Cosmology

@misc{hill1823an9,
    author = "Hill, I",
    title = "An abstract of a new theory of the formation of the earth",
    year = "1823",
    howpublished = "Baltimore, N.G. Maxwell, 211 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Hill, I., 1823, An abstract of a new theory of the formation of the earth: Baltimore, N.G. Maxwell, 211 p.}"
}

In the application of relativistic mechanics and relativistic thermodynamics to cosmology, it has been usual to consider homogeneous models of the universe, filled with an idealized fluid, which at any given time has the same properties throughout the whole of its spatial extent. This procedure has a certain heuristic justification on account of the greater mathematical simplicity of homogeneous as compared with non-homogeneous models, and has a measure of observational justification on account of the approximate uniformity in the large scale distribution of extra-galactic nebulae, which is found out to the some 108 light-years which the Mount Wilson 100-inch telescope has been able to penetrate. Nevertheless, it is evident that some preponderating tendency for inhomogeneities to disappear with time would have to be demonstrated, before such models could be used with confidence to obtain extrapolated conclusions as to the behavior of the universe in very distant regions or over exceedingly long periods of time.

@article{doi101073pnas203169,
    author = "Tolman, Richard C.",
    title = "Effect of Inhomogeneity on Cosmological Models",
    year = "1934",
    journal = "Proceedings of the National Academy of Sciences",
    abstract = "In the application of relativistic mechanics and relativistic thermodynamics to cosmology, it has been usual to consider homogeneous models of the universe, filled with an idealized fluid, which at any given time has the same properties throughout the whole of its spatial extent. This procedure has a certain heuristic justification on account of the greater mathematical simplicity of homogeneous as compared with non-homogeneous models, and has a measure of observational justification on account of the approximate uniformity in the large scale distribution of extra-galactic nebulae, which is found out to the some 108 light-years which the Mount Wilson 100-inch telescope has been able to penetrate. Nevertheless, it is evident that some preponderating tendency for inhomogeneities to disappear with time would have to be demonstrated, before such models could be used with confidence to obtain extrapolated conclusions as to the behavior of the universe in very distant regions or over exceedingly long periods of time.",
    url = "https://doi.org/10.1073/pnas.20.3.169",
    doi = "10.1073/pnas.20.3.169",
    openalex = "W3021615542"
}

@book{hauret1955origines8,
    author = "Hauret, C",
    title = "Origines de l'univers et de l'homme d'apres la Bible [Beginnings",
    year = "1955",
    publisher = "Genesis and Modern Science]: Dubuque, Priory Press, 304 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Hauret, C., 1955, Origines de l'univers et de l'homme d'apres la Bible [Beginnings: Genesis and Modern Science]: Dubuque, Priory Press, 304 p.}"
}

@misc{teilharddechardin1961hymne15,
    author = "Teilhard de Chardin, P",
    title = "Hymne de l'univers. La Messe sur le monde. Trois histoires comme Benson.La Puissance spirituelle de la matiere. Pensees choisies par Fernande Tardivel",
    year = "1961",
    howpublished = "Paris, Editions du Seuil, 246 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Teilhard de Chardin, P., 1961, Hymne de l'univers. La Messe sur le monde. Trois histoires comme Benson.La Puissance spirituelle de la matiere. Pensees choisies par Fernande Tardivel: Paris, Editions du Seuil, 246 p.}"
}

@misc{mccrea1968cosmology13,
    author = "McCrea, W. H",
    title = "Cosmology after half a century",
    year = "1968",
    howpublished = "Science, v. 160, p. 1295- 1299",
    note = "talkorigins\_source = {true}; raw\_reference = {McCrea, W. H., 1968, Cosmology after half a century: Science, v. 160, p. 1295- 1299.}"
}

@book{laird1969theism11,
    author = "Laird, J",
    title = "Theism and Cosmology",
    year = "1969",
    publisher = "Freeport, Books for Libraries Press",
    note = "talkorigins\_source = {true}; raw\_reference = {Laird, J., 1969, Theism and Cosmology: Freeport, Books for Libraries Press.}"
}

@book{morris1970biblical14,
    author = "Morris, H. M",
    title = "Biblical Cosmology and Modern Science",
    year = "1970",
    publisher = "Nutley, New Jersey, Craig Press",
    note = "talkorigins\_source = {true}; raw\_reference = {Morris, H. M., 1970, Biblical Cosmology and Modern Science: Nutley, New Jersey, Craig Press.}"
}

@misc{edwards1974the6,
    author = "Edwards, P",
    title = "The Cosmological Argument, in Brody, B., ed., Readings in the Philosophy of Religion",
    year = "1974",
    howpublished = "Englewood Cliffs, Prentice-Hall",
    note = "talkorigins\_source = {true}; raw\_reference = {Edwards, P., 1974, The Cosmological Argument, in Brody, B., ed., Readings in the Philosophy of Religion: Englewood Cliffs, Prentice-Hall.}"
}

@article{young1974the20,
    author = "Young, J. Z",
    title = "The George Bidder Lecture 1973. Brains and worlds",
    year = "1974",
    journal = "the cerebral cosmologies: Journal of Experimental Biology, v. 61, p. 5-17",
    note = "talkorigins\_source = {true}; raw\_reference = {Young, J. Z., 1974, The George Bidder Lecture 1973. Brains and worlds: the cerebral cosmologies: Journal of Experimental Biology, v. 61, p. 5-17.}"
}

@article{cowen1978the3,
    author = "Cowen, R. C",
    title = "The cosmic cradle",
    year = "1978",
    journal = "Technology Review, v. 80, no. 5, p. 6-7, 19",
    note = "talkorigins\_source = {true}; raw\_reference = {Cowen, R. C., 1978, The cosmic cradle: Technology Review, v. 80, no. 5, p. 6-7, 19.}"
}

@misc{horigan1979chance10,
    author = "Horigan, J. E",
    title = "Chance or Design?",
    year = "1979",
    howpublished = "New York, Philosophical Library, 233 p",
    note = "talkorigins\_source = {true}; raw\_reference = {Horigan, J. E., 1979, Chance or Design?: New York, Philosophical Library, 233 p.}"
}

@incollection{kourganoff1980relativistic,
    author = "Kourganoff, V.",
    title = "Relativistic Effects in Observational Cosmology. The Cosmological Redshift in Expanding Universe",
    year = "1980",
    booktitle = "Introduction to Advanced Astrophysics",
    url = "https://doi.org/10.1007/978-94-009-9468-3\_12",
    doi = "10.1007/978-94-009-9468-3\_12",
    openalex = "W2480454805",
    pages = "383-433",
    references = "doi101086143726, doi101086147041, doi101112plmss242190, doi1011341226719950721, openalexw1664136895, openalexw2600339924, openalexw3040856923, openalexw567317526"
}

@misc{chaisson1981cosmic2,
    author = "Chaisson, E",
    title = "Cosmic Dawn",
    year = "1981",
    howpublished = "The Origins of Matter and Life: Boston, Little, Brown",
    note = "talkorigins\_source = {true}; raw\_reference = {Chaisson, E., 1981, Cosmic Dawn: The Origins of Matter and Life: Boston, Little, Brown.}"
}

@article{dutch1982a5,
    author = "Dutch, S. L",
    title = "A critique of creationist cosmology",
    year = "1982",
    journal = "Journal of Geological Education, v. 30, p. 27-33",
    note = "talkorigins\_source = {true}; raw\_reference = {Dutch, S. L., 1982, A critique of creationist cosmology: Journal of Geological Education, v. 30, p. 27-33.}"
}

@misc{davies1983god4,
    author = "Davies, P",
    title = "God and the New Physics",
    year = "1983",
    howpublished = "New York, Simon and Schuster",
    note = "talkorigins\_source = {true}; raw\_reference = {Davies, P., 1983, God and the New Physics: New York, Simon and Schuster.}"
}

@misc{thomsen1983a17,
    author = "Thomsen, D. E",
    title = "A knowing universe seeking to be known",
    year = "1983",
    howpublished = "Science News, v. 123, p. 124",
    note = "talkorigins\_source = {true}; raw\_reference = {Thomsen, D. E., 1983, A knowing universe seeking to be known: Science News, v. 123, p. 124.}"
}

@misc{thomsen1983the16,
    author = "Thomsen, D. E",
    title = "The new inflationary nothing cosmology",
    year = "1983",
    howpublished = "Science News, v. 123, p. 108-109",
    note = "talkorigins\_source = {true}; raw\_reference = {Thomsen, D. E., 1983, The new inflationary nothing cosmology: Science News, v. 123, p. 108-109.}"
}

@inproceedings{gentry1984radioactive7,
    author = "Gentry, R. V",
    title = "Radioactive Halos in a Radiochronological and Cosmological Perspective, in Awbery, F. T., and Thwaites, W. M., eds., Evolutionists Confront Creationists",
    year = "1984",
    booktitle = "San Francisco, Ca., American Association for the Advancement of Science, v. 1, Part 3, p. 38-65; Proceedings of the 63rd Annual Meeting of the Pacific Division",
    note = "talkorigins\_source = {true}; raw\_reference = {Gentry, R. V., 1984, Radioactive Halos in a Radiochronological and Cosmological Perspective, in Awbery, F. T., and Thwaites, W. M., eds., Evolutionists Confront Creationists: San Francisco, Ca., American Association for the Advancement of Science, v. 1, Part 3, p. 38-65; Proceedings of the 63rd Annual Meeting of the Pacific Division.}"
}

@misc{tyron1984what18,
    author = "Tyron, E",
    title = "What made the world?",
    year = "1984",
    howpublished = "New Scientist, v. 101, p. 14",
    note = "talkorigins\_source = {true}; raw\_reference = {Tyron, E., 1984, What made the world?: New Scientist, v. 101, p. 14.}"
}

@misc{waldrop1984before19,
    author = "Waldrop, M. M",
    title = "Before the beginning",
    year = "1984",
    howpublished = "Science 84, v. 5, no. 1, p. 45-51",
    note = "talkorigins\_source = {true}; raw\_reference = {Waldrop, M. M., 1984, Before the beginning: Science 84, v. 5, no. 1, p. 45-51.}"
}

@misc{bartusaik1987before1,
    author = "Bartusaik, M",
    title = "Before the Big Bang",
    year = "1987",
    howpublished = "The Big Foam: Discover, v. 8, p. 76- 83",
    note = "talkorigins\_source = {true}; raw\_reference = {Bartusaik, M., 1987, Before the Big Bang: The Big Foam: Discover, v. 8, p. 76- 83.}"
}

@misc{mallove1987the12,
    author = "Mallove, E. F",
    title = "The Quickening Universe",
    year = "1987",
    howpublished = "Cosmic Evolution and Human Destiny: New York, St. Martin's",
    note = "talkorigins\_source = {true}; raw\_reference = {Mallove, E. F., 1987, The Quickening Universe: Cosmic Evolution and Human Destiny: New York, St. Martin's.}"
}

We present a new method for calculating linear cosmic microwave background (CMB) anisotropy spectra based on integration over sources along the photon past light cone. In this approach the temperature anisotropy is written as a time integral over the product of a geometrical term and a source term. The geometrical term is given by radial eigenfunctions which do not depend on the particular cosmological model. The source term can be expressed in terms of photon, baryon and metric perturbations, all of which can be calculated using a small number of differential equations. This split clearly separates between the dynamical and geometrical effects on the CMB anisotropies. More importantly, it allows to significantly reduce the computational time compared to standard methods. This is achieved because the source term, which depends on the model and is generally the most time consuming part of calculation, is a slowly varying function of wavelength and needs to be evaluated only in a small number of points. The geometrical term, which oscillates much more rapidly than the source term, does not depend on the particular model and can be precomputed in advance. Standard methods that do not separate the two terms and require a much higher number of evaluations. The new method leads to about two orders of magnitude reduction in CPU time when compared to standard methods and typically requires a few minutes on a workstation for a single model. The method should be especially useful for accurate determinations of cosmological parameters from CMB anisotropy and polarization measurements that will become possible with the next generation of experiments. A programm implementing this method can be obtained from the authors. Subject headings: cosmology: cosmic microwave background, cosmology: large-scale structure of the universe, gravitation, cosmology: dark matter – 2 – 1.

@article{openalexw3106449272,
    author = "Zaldarriaga, Matias",
    title = "A line of sight integration approach to cosmic microwave background anisotropies",
    year = "1996",
    abstract = "We present a new method for calculating linear cosmic microwave background (CMB) anisotropy spectra based on integration over sources along the photon past light cone. In this approach the temperature anisotropy is written as a time integral over the product of a geometrical term and a source term. The geometrical term is given by radial eigenfunctions which do not depend on the particular cosmological model. The source term can be expressed in terms of photon, baryon and metric perturbations, all of which can be calculated using a small number of differential equations. This split clearly separates between the dynamical and geometrical effects on the CMB anisotropies. More importantly, it allows to significantly reduce the computational time compared to standard methods. This is achieved because the source term, which depends on the model and is generally the most time consuming part of calculation, is a slowly varying function of wavelength and needs to be evaluated only in a small number of points. The geometrical term, which oscillates much more rapidly than the source term, does not depend on the particular model and can be precomputed in advance. Standard methods that do not separate the two terms and require a much higher number of evaluations. The new method leads to about two orders of magnitude reduction in CPU time when compared to standard methods and typically requires a few minutes on a workstation for a single model. The method should be especially useful for accurate determinations of cosmological parameters from CMB anisotropy and polarization measurements that will become possible with the next generation of experiments. A programm implementing this method can be obtained from the authors. Subject headings: cosmology: cosmic microwave background, cosmology: large-scale structure of the universe, gravitation, cosmology: dark matter – 2 – 1.",
    openalex = "W3106449272"
}

We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 z 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-z Supernova Search Team and recent results by Riess et al., this expanded set of 16 high-redshift M \ 1) methods. We estimate the dynamical age of the universe to be 14.2 ^1.7 Gyr including systematic uncertainties in the current Cepheid distance scale. We estimate the likely e ect of several sources of systematic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these e ects appear to reconcile the data with and) " \ 0 q 0 0.

@article{doi101086300499,
    author = "Riess, Adam G. and Filippenko, A. V. and Challis, P. and Clocchiatti, A. and Diercks, Alan H. and Garnavich, P. and Gilliland, Ron and Hogan, Craig J. and Jha, Saurabh W. and Kirshner, R. and Leibundgut, B. and Phillips, M. M. and Reiss, David J. and Schmidt, B. and Schommer, R. A. and Smith, R. Chris and Spyromilio, J. and Stubbs, C. W. and Suntzeff, N. B. and Tonry, J.",
    title = "Observational Evidence from Supernovae for an Accelerating Universe and a Cosmological Constant",
    year = "1998",
    journal = "The Astronomical Journal",
    abstract = {We present spectral and photometric observations of 10 Type Ia supernovae (SNe Ia) in the redshift range 0.16 z 0.62. The luminosity distances of these objects are determined by methods that employ relations between SN Ia luminosity and light curve shape. Combined with previous data from our High-z Supernova Search Team and recent results by Riess et al., this expanded set of 16 high-redshift M \ 1) methods. We estimate the dynamical age of the universe to be 14.2 ^1.7 Gyr including systematic uncertainties in the current Cepheid distance scale. We estimate the likely e ect of several sources of systematic error, including progenitor and metallicity evolution, extinction, sample selection bias, local perturbations in the expansion rate, gravitational lensing, and sample contamination. Presently, none of these e ects appear to reconcile the data with and) " \ 0 q 0 0.},
    url = "https://doi.org/10.1086/300499",
    doi = "10.1086/300499",
    openalex = "W2073832139"
}

The High-Z Supernova Search is an international collaboration to discover and monitor type Ia supernovae (SN Ia) at $z > 0.2$ with the aim of measuring cosmic deceleration and global curvature. Our collaboration has pursued a basic understanding of supernovae in the nearby Universe, discovering and observing a large sample of objects, and developing methods to measure accurate distances with SN Ia. This paper describes the extension of this program to $z \\geq 0.2$, outlining our search techniques and follow-up program. We have devised high-throughput filters which provide accurate two-color restframe $B$ and $V$ light curves of SN Ia, enabling us to produce precise, extinction-corrected luminosity distances in the range $0.25 < z < 0.55$. Sources of systematic error from K-corrections, extinction, selection effects, and evolution are investigated, and their effects estimated. We present photometric and spectral observations of SN 1995K, our program's first supernova, and use the data to obtain a precise measurement of the luminosity distance to the $z=0.479$ host galaxy. This object, when combined with a nearby sample of SN, yields an estimate for the matter density of the Universe of $\\Omega_M = -0.2^{+1.0}_{-0.8}$ if $\\Omega_\\Lambda = 0$. For a spatially flat universe composed of normal matter and a cosmological constant, we find $\\Omega_M = 0.4^{+0.5}_{-0.4}$, $\\Omega_\\Lambda = 0.6^{+0.4}_{-0.5}$. We demonstrate that with a sample of $\\sim 30$ objects, we should be able to determine relative luminosity distances over the range $0 < z< 0.5$ with sufficient precision to measure $\\Omega_M$ with an uncertainty of $\\pm 0.2$.

@article{doi101086306308,
    author = "Schmidt, B. and Suntzeff, N. B. and Phillips, M. M. and Schommer, R. A. and Clocchiatti, A. and Kirshner, R. and Garnavich, P. and Challis, P. and Leibundgut, B. and Spyromilio, J. and Riess, Adam G. and Filippenko, A. V. and Hamuy, M. and Smith, R. Chris and Hogan, Craig J. and Stubbs, C. W. and Diercks, Alan H. and Reiss, David J. and Gilliland, Ron and Tonry, J. and Maza, J. and Dressler, Alan and Walsh, J. R. and Ciardullo, Robin",
    title = "The High‐Z Supernova Search: Measuring Cosmic Deceleration and Global Curvature of the Universe Using Type Ia Supernovae",
    year = "1998",
    journal = "The Astrophysical Journal",
    abstract = "The High-Z Supernova Search is an international collaboration to discover and monitor type Ia supernovae (SN Ia) at $z > 0.2$ with the aim of measuring cosmic deceleration and global curvature. Our collaboration has pursued a basic understanding of supernovae in the nearby Universe, discovering and observing a large sample of objects, and developing methods to measure accurate distances with SN Ia. This paper describes the extension of this program to $z \\geq 0.2$, outlining our search techniques and follow-up program. We have devised high-throughput filters which provide accurate two-color restframe $B$ and $V$ light curves of SN Ia, enabling us to produce precise, extinction-corrected luminosity distances in the range $0.25 < z < 0.55$. Sources of systematic error from K-corrections, extinction, selection effects, and evolution are investigated, and their effects estimated. We present photometric and spectral observations of SN 1995K, our program's first supernova, and use the data to obtain a precise measurement of the luminosity distance to the $z=0.479$ host galaxy. This object, when combined with a nearby sample of SN, yields an estimate for the matter density of the Universe of $\\Omega\_M = -0.2^{+1.0}\_{-0.8}$ if $\\Omega\_\\Lambda = 0$. For a spatially flat universe composed of normal matter and a cosmological constant, we find $\\Omega\_M = 0.4^{+0.5}\_{-0.4}$, $\\Omega\_\\Lambda = 0.6^{+0.4}\_{-0.5}$. We demonstrate that with a sample of $\\sim 30$ objects, we should be able to determine relative luminosity distances over the range $0 < z< 0.5$ with sufficient precision to measure $\\Omega\_M$ with an uncertainty of $\\pm 0.2$.",
    url = "https://doi.org/10.1086/306308",
    doi = "10.1086/306308",
    openalex = "W2146293885",
    references = "doi101086147041, doi101112plmss242190, doi105860choice311499"
}

We propose a cosmological scenario in which the hot big bang universe is produced by the collision of a brane in the bulk space with a bounding orbifold plane, beginning from an otherwise cold, vacuous, static universe. The model addresses the cosmological horizon, flatness and monopole problems and generates a nearly scale-invariant spectrum of density perturbations without invoking superluminal expansion (inflation). The scenario relies, instead, on physical phenomena that arise naturally in theories based on extra dimensions and branes. As an example, we present our scenario predominantly within the context of heterotic M theory. A prediction that distinguishes this scenario from standard inflationary cosmology is a strongly blue gravitational wave spectrum, which has consequences for microwave background polarization experiments and gravitational wave detectors.

@article{doi101103physrevd64123522,
    author = "Khoury, Justin and Ovrut, Burt A. and Steinhardt, Paul J. and Turok, Neil",
    title = "Ekpyrotic universe: Colliding branes and the origin of the hot big bang",
    year = "2001",
    journal = "Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D. Particles and fields",
    abstract = "We propose a cosmological scenario in which the hot big bang universe is produced by the collision of a brane in the bulk space with a bounding orbifold plane, beginning from an otherwise cold, vacuous, static universe. The model addresses the cosmological horizon, flatness and monopole problems and generates a nearly scale-invariant spectrum of density perturbations without invoking superluminal expansion (inflation). The scenario relies, instead, on physical phenomena that arise naturally in theories based on extra dimensions and branes. As an example, we present our scenario predominantly within the context of heterotic M theory. A prediction that distinguishes this scenario from standard inflationary cosmology is a strongly blue gravitational wave spectrum, which has consequences for microwave background polarization experiments and gravitational wave detectors.",
    url = "https://doi.org/10.1103/physrevd.64.123522",
    doi = "10.1103/physrevd.64.123522",
    openalex = "W2029143135",
    references = "doi101016037015739290044z, doi1010160370269382912199, doi101016s0370269398004663, doi101016s0370269398008600, doi101103physrevd23347, doi101103physrevd59086004, doi101103physrevlett481220, doi101103physrevlett491110, doi101103physrevlett833370, doi101103physrevlett834690"
}

WMAP precision data enables accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat Lambda-dominated universe seeded by nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data. With parameters fixed only by WMAP data, we can fit finer scale CMB measurements and measurements of large scle structure (galaxy surveys and the Lyman alpha forest). This simple model is also consistent with a host of other astronomical measurements. We then fit the model parameters to a combination of WMAP data with other finer scale CMB experiments (ACBAR and CBI), 2dFGRS measurements and Lyman alpha forest data to find the model's best fit cosmological parameters: h=0.71+0.04-0.03, Omega_b h^2=0.0224+-0.0009, Omega_m h^2=0.135+0.008-0.009, tau=0.17+-0.06, n_s(0.05/Mpc)=0.93+-0.03, and sigma_8=0.84+-0.04. WMAP's best determination of tau=0.17+-0.04 arises directly from the TE data and not from this model fit, but they are consistent. These parameters imply that the age of the universe is 13.7+-0.2 Gyr. The data favors but does not require a slowly varying spectral index. By combining WMAP data with other astronomical data sets, we constrain the geometry of the universe, Omega_tot = 1.02 +- 0.02, the equation of state of the dark energy w = -1), and the energy density in stable neutrinos, Omega_nu h^2 < 0.0076 (95% confidence limit). For 3 degenerate neutrino species, this limit implies that their mass is less than 0.23 eV (95% confidence limit). The WMAP detection of early reionization rules out warm dark matter.

@article{doi101086377226,
    author = "Spergel, David N. and Verde, Licia and Peiris, Hiranya V. and Komatsu, Eiichiro and Nolta, M. R. and Bennett, C. L. and Halpern, M. and Hinshaw, G. and Jarosik, N. and Kogut, A. and Limon, M. and Meyer, S. S. and Page, Lyman A. and Tucker, Gregory S. and Weiland, J. L. and Wollack, Edward J. and Wright, E. L.",
    title = "First‐Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Determination of Cosmological Parameters",
    year = "2003",
    journal = "The Astrophysical Journal Supplement Series",
    abstract = "WMAP precision data enables accurate testing of cosmological models. We find that the emerging standard model of cosmology, a flat Lambda-dominated universe seeded by nearly scale-invariant adiabatic Gaussian fluctuations, fits the WMAP data. With parameters fixed only by WMAP data, we can fit finer scale CMB measurements and measurements of large scle structure (galaxy surveys and the Lyman alpha forest). This simple model is also consistent with a host of other astronomical measurements. We then fit the model parameters to a combination of WMAP data with other finer scale CMB experiments (ACBAR and CBI), 2dFGRS measurements and Lyman alpha forest data to find the model's best fit cosmological parameters: h=0.71+0.04-0.03, Omega\_b h^2=0.0224+-0.0009, Omega\_m h^2=0.135+0.008-0.009, tau=0.17+-0.06, n\_s(0.05/Mpc)=0.93+-0.03, and sigma\_8=0.84+-0.04. WMAP's best determination of tau=0.17+-0.04 arises directly from the TE data and not from this model fit, but they are consistent. These parameters imply that the age of the universe is 13.7+-0.2 Gyr. The data favors but does not require a slowly varying spectral index. By combining WMAP data with other astronomical data sets, we constrain the geometry of the universe, Omega\_tot = 1.02 +- 0.02, the equation of state of the dark energy w = -1), and the energy density in stable neutrinos, Omega\_nu h^2 < 0.0076 (95\% confidence limit). For 3 degenerate neutrino species, this limit implies that their mass is less than 0.23 eV (95\% confidence limit). The WMAP detection of early reionization rules out warm dark matter.",
    url = "https://doi.org/10.1086/377226",
    doi = "10.1086/377226",
    openalex = "W2118265220",
    references = "doi1010160550321388901939, doi101046j13658711199902692x, doi101086300499, doi101086304888, doi101086307221, doi101086320638, doi101086377253, doi101103physrevd373406, doi101103physrevd68023509, doi101103physrevlett801582, openalexw3100110286"
}

Physics welcomes the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, \ensuremath{\Lambda}; today the concept is termed dark energy or quintessence. Physics also suggests that dark energy could be dynamical, allowing for the arguably appealing picture of an evolving dark-energy density approaching its natural value, zero, and small now because the expanding universe is old. This would alleviate the classical problem of the curious energy scale of a millielectron volt associated with a constant \ensuremath{\Lambda}. Dark energy may have been detected by recent cosmological tests. These tests make a good scientific case for the context, in the relativistic Friedmann-Lema\^{\i}tre model, in which the gravitational inverse-square law is applied to the scales of cosmology. We have well-checked evidence that the mean mass density is not much more than one-quarter of the critical Einstein--de Sitter value. The case for detection of dark energy is not yet as convincing but still serious; we await more data, which may be derived from work in progress. Planned observations may detect the evolution of the dark-energy density; a positive result would be a considerable stimulus for attempts at understanding the microphysics of dark energy. This review presents the basic physics and astronomy of the subject, reviews the history of ideas, assesses the state of the observational evidence, and comments on recent developments in the search for a fundamental theory.

@article{doi101103revmodphys75559,
    author = "Peebles, P. J. E. and Ratra, Bharat",
    title = "The cosmological constant and dark energy",
    year = "2003",
    journal = "Reviews of Modern Physics",
    abstract = "Physics welcomes the idea that space contains energy whose gravitational effect approximates that of Einstein's cosmological constant, \ensuremath{\Lambda}; today the concept is termed dark energy or quintessence. Physics also suggests that dark energy could be dynamical, allowing for the arguably appealing picture of an evolving dark-energy density approaching its natural value, zero, and small now because the expanding universe is old. This would alleviate the classical problem of the curious energy scale of a millielectron volt associated with a constant \ensuremath{\Lambda}. Dark energy may have been detected by recent cosmological tests. These tests make a good scientific case for the context, in the relativistic Friedmann-Lema\^{\i}tre model, in which the gravitational inverse-square law is applied to the scales of cosmology. We have well-checked evidence that the mean mass density is not much more than one-quarter of the critical Einstein--de Sitter value. The case for detection of dark energy is not yet as convincing but still serious; we await more data, which may be derived from work in progress. Planned observations may detect the evolution of the dark-energy density; a positive result would be a considerable stimulus for attempts at understanding the microphysics of dark energy. This review presents the basic physics and astronomy of the subject, reviews the history of ideas, assesses the state of the observational evidence, and comments on recent developments in the search for a fundamental theory.",
    url = "https://doi.org/10.1103/revmodphys.75.559",
    doi = "10.1103/revmodphys.75.559",
    openalex = "W2073603601",
    references = "doi101007bf00653471, doi101007bf01332580, doi10106313067575, doi101073pnas153168, doi101086147041, doi101086186504, doi101086311074, doi101093mnras1085372, doi101093mnras1166662, doi101103physrevd23347, doi101103physrevd58043506, doi101103physrevlett592607, doi10111911934936, doi101142s0218271800000542, doi105860choice311499"
}

Cosmology is an unusual science with an unusual history. This bookexamines the formative years of modern cosmology from the perspectiveof its interaction with religious thought. As the first study of itskind, it reveals how closely associated the development of cosmologyhas been with considerations of a philosophical and religiousnature.

@book{doi1011429781860946042,
    author = "Kragh, Helge",
    title = "Matter And Spirit in the Universe - Scientific and Religious Preludes to Modern Cosmology",
    year = "2004",
    booktitle = "History of modern physical sciences",
    abstract = "Cosmology is an unusual science with an unusual history. This bookexamines the formative years of modern cosmology from the perspectiveof its interaction with religious thought. As the first study of itskind, it reveals how closely associated the development of cosmologyhas been with considerations of a philosophical and religiousnature.",
    url = "https://doi.org/10.1142/9781860946042",
    doi = "10.1142/9781860946042",
    openalex = "W1537866359"
}

Quantum gravity is expected to be necessary in order to understand situations where classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical space-time inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding space-time is then modified. One particular realization is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. Main effects are introduced into effective classical equations which allow to avoid interpretational problems of quantum theory. They give rise to new kinds of early universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function which allows to extend space-time beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of space-time arising in loop quantum gravity and its application to cosmology sheds new light on more general issues such as time. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.12942/lrr-2005-11.

@article{doi1012942lrr200511,
    author = "Bojowald, Martin",
    title = "Loop Quantum Cosmology",
    year = "2005",
    journal = "Living Reviews in Relativity",
    abstract = "Quantum gravity is expected to be necessary in order to understand situations where classical general relativity breaks down. In particular in cosmology one has to deal with initial singularities, i.e., the fact that the backward evolution of a classical space-time inevitably comes to an end after a finite amount of proper time. This presents a breakdown of the classical picture and requires an extended theory for a meaningful description. Since small length scales and high curvatures are involved, quantum effects must play a role. Not only the singularity itself but also the surrounding space-time is then modified. One particular realization is loop quantum cosmology, an application of loop quantum gravity to homogeneous systems, which removes classical singularities. Its implications can be studied at different levels. Main effects are introduced into effective classical equations which allow to avoid interpretational problems of quantum theory. They give rise to new kinds of early universe phenomenology with applications to inflation and cyclic models. To resolve classical singularities and to understand the structure of geometry around them, the quantum description is necessary. Classical evolution is then replaced by a difference equation for a wave function which allows to extend space-time beyond classical singularities. One main question is how these homogeneous scenarios are related to full loop quantum gravity, which can be dealt with at the level of distributional symmetric states. Finally, the new structure of space-time arising in loop quantum gravity and its application to cosmology sheds new light on more general issues such as time. ELECTRONIC SUPPLEMENTARY MATERIAL: Supplementary material is available for this article at 10.12942/lrr-2005-11.",
    url = "https://doi.org/10.12942/lrr-2005-11",
    doi = "10.12942/lrr-2005-11",
    openalex = "W2109902906",
    references = "doi101016055032139500150q, doi101017cbo9780511524646, doi101017cbo9780511755804, doi101088026493812115r01, doi101098rspa19700021, doi101103physrev1601113, doi101103physrevd282960, doi101103physrevd361587, doi101103physrevd64123522, doi101103physrevlett572244"
}

@article{moffat2005cosmic,
    author = "Moffat, J W",
    title = "Cosmic microwave background, accelerating universe and inhomogeneous cosmology",
    year = "2005",
    journal = "Journal of Cosmology and Astroparticle Physics",
    url = "https://doi.org/10.1088/1475-7516/2005/10/012",
    doi = "10.1088/1475-7516/2005/10/012",
    number = "10",
    openalex = "W2006634252",
    pages = "012-012",
    volume = "2005",
    references = "doi101073pnas203169, doi101086148982, doi101086186504, doi101086300499, doi101086307221, doi101086310075, doi101086377226, doi101086377253, doi101086427976, doi101103revmodphys75559"
}

We identify 31 dimensionless physical constants required by particle physics and cosmology, and emphasize that both microphysical constraints and selection effects might help elucidate their origin. Axion cosmology provides an instructive example, in which these two kinds of arguments must both be taken into account, and work well together. If a Peccei-Quinn phase transition occurred before or during inflation, then the axion dark matter density will vary from place to place with a probability distribution. By calculating the net dark matter halo formation rate as a function of all four relevant cosmological parameters and assessing other constraints, we find that this probability distribution, computed at stable solar systems, is arguably peaked near the observed dark matter density. If cosmologically relevant weakly interacting massive particle (WIMP) dark matter is discovered, then one naturally expects comparable densities of WIMPs and axions, making it important to follow up with precision measurements to determine whether WIMPs account for all of the dark matter or merely part of it.

@article{doi101103physrevd73023505,
    author = "Tegmark, Max and Aguirre, Anthony and Rees, M. J. and Wilczek, Frank",
    title = "Dimensionless constants, cosmology, and other dark matters",
    year = "2006",
    journal = "Physical review. D. Particles, fields, gravitation, and cosmology/Physical review. D, Particles, fields, gravitation, and cosmology",
    abstract = "We identify 31 dimensionless physical constants required by particle physics and cosmology, and emphasize that both microphysical constraints and selection effects might help elucidate their origin. Axion cosmology provides an instructive example, in which these two kinds of arguments must both be taken into account, and work well together. If a Peccei-Quinn phase transition occurred before or during inflation, then the axion dark matter density will vary from place to place with a probability distribution. By calculating the net dark matter halo formation rate as a function of all four relevant cosmological parameters and assessing other constraints, we find that this probability distribution, computed at stable solar systems, is arguably peaked near the observed dark matter density. If cosmologically relevant weakly interacting massive particle (WIMP) dark matter is discovered, then one naturally expects comparable densities of WIMPs and axions, making it important to follow up with precision measurements to determine whether WIMPs account for all of the dark matter or merely part of it.",
    url = "https://doi.org/10.1103/physrevd.73.023505",
    doi = "10.1103/physrevd.73.023505",
    openalex = "W1978483279",
    references = "openalexw2600339924"
}

@article{crossref2009the,
    title = "The Birds and the Dinosaurs",
    year = "2009",
    journal = "Science",
    url = "https://doi.org/10.1126/science.324\_565d",
    doi = "10.1126/science.324\_565d",
    number = "5927",
    pages = "565-565",
    volume = "324"
}

We propose a model for a power-counting renormalizable field theory living in a fractal spacetime. The action is Lorentz covariant and equipped with a Stieltjes measure. The system flows, even in a classical sense, from an ultraviolet regime where spacetime has Hausdorff dimension 2 to an infrared limit coinciding with a standard D-dimensional field theory. We discuss the properties of a scalar field model at classical and quantum level. Classically, the field lives on a fractal which exchanges energy-momentum with the bulk of integer topological dimension D. Although an observer experiences dissipation, the total energy-momentum is conserved. The field spectrum is a continuum of massive modes. The gravitational sector and Einstein equations are discussed in detail, also on cosmological backgrounds. We find ultraviolet cosmological solutions and comment on their implications for the early universe.

@article{doi101007jhep032010120,
    author = "Calcagni, Gianluca",
    title = "Quantum field theory, gravity and cosmology in a fractal universe",
    year = "2010",
    journal = "Journal of High Energy Physics",
    abstract = "We propose a model for a power-counting renormalizable field theory living in a fractal spacetime. The action is Lorentz covariant and equipped with a Stieltjes measure. The system flows, even in a classical sense, from an ultraviolet regime where spacetime has Hausdorff dimension 2 to an infrared limit coinciding with a standard D-dimensional field theory. We discuss the properties of a scalar field model at classical and quantum level. Classically, the field lives on a fractal which exchanges energy-momentum with the bulk of integer topological dimension D. Although an observer experiences dissipation, the total energy-momentum is conserved. The field spectrum is a continuum of massive modes. The gravitational sector and Einstein equations are discussed in detail, also on cosmological backgrounds. We find ultraviolet cosmological solutions and comment on their implications for the early universe.",
    url = "https://doi.org/10.1007/jhep03(2010)120",
    doi = "10.1007/jhep03(2010)120",
    openalex = "W2010195969",
    references = "doi1011341226719950721"
}

The apparent accelerating expansion of the Universe is forcing us to examine the foundational aspects of the standard model of cosmology -- in particular, the fact that dark energy is a direct consequence of the homogeneity assumption. We discuss the foundations of the assumption of spatial homogeneity, in the case when the Copernican Principle is adopted. We present results that show how (almost-) homogeneity follows from (almost-) isotropy of various observables. The analysis requires the fully nonlinear field equations -- i.e., it is not possible to use second- or higher-order perturbation theory, since one cannot assume a homogeneous and isotropic background. Then we consider what happens if the Copernican Principle is abandoned in our Hubble volume. The simplest models are inhomogeneous but spherically symmetric universes which do not require dark energy to fit the distance modulus. Key problems in these models are to compute the CMB anisotropies and the features of large-scale structure. We review how to construct perturbation theory on a non-homogeneous cosmological background, and discuss the complexities that arise in using this to determine the growth of large-scale structure.

@article{doi101088026493812712124008,
    author = "Clarkson, Chris and Maartens, Roy",
    title = "Inhomogeneity and the foundations of concordance cosmology",
    year = "2010",
    journal = "Classical and Quantum Gravity",
    abstract = "The apparent accelerating expansion of the Universe is forcing us to examine the foundational aspects of the standard model of cosmology -- in particular, the fact that dark energy is a direct consequence of the homogeneity assumption. We discuss the foundations of the assumption of spatial homogeneity, in the case when the Copernican Principle is adopted. We present results that show how (almost-) homogeneity follows from (almost-) isotropy of various observables. The analysis requires the fully nonlinear field equations -- i.e., it is not possible to use second- or higher-order perturbation theory, since one cannot assume a homogeneous and isotropic background. Then we consider what happens if the Copernican Principle is abandoned in our Hubble volume. The simplest models are inhomogeneous but spherically symmetric universes which do not require dark energy to fit the distance modulus. Key problems in these models are to compute the CMB anisotropies and the features of large-scale structure. We review how to construct perturbation theory on a non-homogeneous cosmological background, and discuss the complexities that arise in using this to determine the growth of large-scale structure.",
    url = "https://doi.org/10.1088/0264-9381/27/12/124008",
    doi = "10.1088/0264-9381/27/12/124008",
    openalex = "W2086773856",
    references = "moffat2005cosmic"
}

Loop quantum cosmology (LQC) is the result of applying principles of loop quantum gravity (LQG) to cosmological settings. The distinguishing feature of LQC is the prominent role played by the quantum geometry effects of LQG. In particular, quantum geometry creates a brand new repulsive force which is totally negligible at low spacetime curvature but rises very rapidly in the Planck regime, overwhelming the classical gravitational attraction. In cosmological models, while Einstein's equations hold to an excellent degree of approximation at low curvature, they undergo major modifications in the Planck regime: for matter satisfying the usual energy conditions, any time a curvature invariant grows to the Planck scale, quantum geometry effects dilute it, thereby resolving singularities of general relativity. Quantum geometry corrections become more sophisticated as the models become richer. In particular, in anisotropic models, there are significant changes in the dynamics of shear potentials which tame their singular behavior in striking contrast to older results on anisotropies in bouncing models. Once singularities are resolved, the conceptual paradigm of cosmology changes and one has to revisit many of the standard issues - e.g. the 'horizon problem' - from a new perspective. Such conceptual issues as well as potential observational consequences of the new Planck scale physics are being explored, especially within the inflationary paradigm. These considerations have given rise to a burst of activity in LQC in recent years, with contributions from quantum gravity experts, mathematical physicists and cosmologists. The goal of this review is to provide an overview of the current state of the art in LQC for three sets of audiences: young researchers interested in entering this area; the quantum gravity community in general and cosmologists who wish to apply LQC to probe modifications in the standard paradigm of the early universe. In this review, effort has been made to streamline the material so that each of these communities can read only the sections they are most interested in, without loss of continuity. © 2011 IOP Publishing Ltd.

@article{doi101088026493812821213001,
    author = "Ashtekar, Abhay and Singh, Parampreet",
    title = "Loop quantum cosmology: a status report",
    year = "2011",
    journal = "Classical and Quantum Gravity",
    abstract = "Loop quantum cosmology (LQC) is the result of applying principles of loop quantum gravity (LQG) to cosmological settings. The distinguishing feature of LQC is the prominent role played by the quantum geometry effects of LQG. In particular, quantum geometry creates a brand new repulsive force which is totally negligible at low spacetime curvature but rises very rapidly in the Planck regime, overwhelming the classical gravitational attraction. In cosmological models, while Einstein's equations hold to an excellent degree of approximation at low curvature, they undergo major modifications in the Planck regime: for matter satisfying the usual energy conditions, any time a curvature invariant grows to the Planck scale, quantum geometry effects dilute it, thereby resolving singularities of general relativity. Quantum geometry corrections become more sophisticated as the models become richer. In particular, in anisotropic models, there are significant changes in the dynamics of shear potentials which tame their singular behavior in striking contrast to older results on anisotropies in bouncing models. Once singularities are resolved, the conceptual paradigm of cosmology changes and one has to revisit many of the standard issues - e.g. the 'horizon problem' - from a new perspective. Such conceptual issues as well as potential observational consequences of the new Planck scale physics are being explored, especially within the inflationary paradigm. These considerations have given rise to a burst of activity in LQC in recent years, with contributions from quantum gravity experts, mathematical physicists and cosmologists. The goal of this review is to provide an overview of the current state of the art in LQC for three sets of audiences: young researchers interested in entering this area; the quantum gravity community in general and cosmologists who wish to apply LQC to probe modifications in the standard paradigm of the early universe. In this review, effort has been made to streamline the material so that each of these communities can read only the sections they are most interested in, without loss of continuity. © 2011 IOP Publishing Ltd.",
    url = "https://doi.org/10.1088/0264-9381/28/21/213001",
    doi = "10.1088/0264-9381/28/21/213001",
    openalex = "W2064559964",
    references = "doi101017cbo9780511524646, doi101017cbo9780511755804, doi1010631531249, doi10108800319112314029, doi10108800670049192218, doi101088026493812115r01, doi101103physrev1601113, doi101103physrevd282960, doi101103physrevd361587, doi101103physrevd525743, doi101103physrevd64123522, doi101103physrevd65126003, doi101103physrevd72333, doi101103physrevd73124038, doi101103physrevd74084003, doi101103physrevlett572244, doi101103physrevlett96141301, doi101103revmodphys20367, doi101142s0218271811018925, doi1012942lrr200511, openalexw2984224373"
}

The backbone of standard cosmology is the Friedmann-Robertson-Walker solution to Einstein's equations of general relativity (GR). In recent years, observations have largely confirmed many of the properties of this model, which are based on a partitioning of the universe's energy density into three primary constituents: matter, radiation and a hypothesized dark energy which, in cold dark matter (CDM), is assumed to be a cosmological constant. Yet with this progress, several unpalatable coincidences (perhaps even inconsistencies) have emerged along with the successful confirmation of expected features. One of these is the observed equality of our gravitational horizon R h (t 0) with the distance ct 0 light has travelled since the big bang, in terms of the current age t 0 of the universe. This equality is very peculiar because it need not have occurred at all and, if it did, should only have happened once (right now) in the context of CDM. In this paper, we propose an explanation for why this equality may actually be required by GR, through the application of Birkhoff's theorem and the Weyl postulate, at least in the case of a flat space-time. If this proposal is correct, R h (t) should be equal to ct for all cosmic time t, not just its present value t 0. Therefore, models such as CDM would be incomplete because they ascribe the cosmic expansion to variable conditions not consistent with this relativistic constraint. We show that this may be the reason why the observed galaxy correlation function is not consistent with the predictions of the standard model. We suggest that an R h = ct universe is easily distinguishable from all other models at large redshift (i.e. in the early universe), where the latter all predict a rapid deceleration.

@article{doi101111j13652966201119906x,
    author = "Melia, Fulvio and Shevchuk, A. S. H.",
    title = "The Rh=ct universe",
    year = "2011",
    journal = "Monthly Notices of the Royal Astronomical Society",
    abstract = "The backbone of standard cosmology is the Friedmann-Robertson-Walker solution to Einstein's equations of general relativity (GR). In recent years, observations have largely confirmed many of the properties of this model, which are based on a partitioning of the universe's energy density into three primary constituents: matter, radiation and a hypothesized dark energy which, in cold dark matter (CDM), is assumed to be a cosmological constant. Yet with this progress, several unpalatable coincidences (perhaps even inconsistencies) have emerged along with the successful confirmation of expected features. One of these is the observed equality of our gravitational horizon R h (t 0) with the distance ct 0 light has travelled since the big bang, in terms of the current age t 0 of the universe. This equality is very peculiar because it need not have occurred at all and, if it did, should only have happened once (right now) in the context of CDM. In this paper, we propose an explanation for why this equality may actually be required by GR, through the application of Birkhoff's theorem and the Weyl postulate, at least in the case of a flat space-time. If this proposal is correct, R h (t) should be equal to ct for all cosmic time t, not just its present value t 0. Therefore, models such as CDM would be incomplete because they ascribe the cosmic expansion to variable conditions not consistent with this relativistic constraint. We show that this may be the reason why the observed galaxy correlation function is not consistent with the predictions of the standard model. We suggest that an R h = ct universe is easily distinguishable from all other models at large redshift (i.e. in the early universe), where the latter all predict a rapid deceleration.",
    url = "https://doi.org/10.1111/j.1365-2966.2011.19906.x",
    doi = "10.1111/j.1365-2966.2011.19906.x",
    openalex = "W2951267753",
    references = "doi101112plmss242190"
}

Assuming the universe is spatially homogeneous on the largest scales lays the foundation for almost all cosmology. This idea is based on the Copernican Principle, that we are not at a particularly special place in the universe. Surprisingly, this philosophical assumption has yet to be rigorously demonstrated independently of the standard paradigm. This issue has been brought to light by cosmological models which can potentially explain apparent acceleration by spatial inhomogeneity rather than dark energy. These models replace the temporal fine tuning associated with Λ with a spatial fine tuning, and so violate the Copernican assumption. While is seems unlikely that such models can really give a realistic solution to the dark energy problem, they do reveal how poorly constrained radial inhomogeneity actually is. So the bigger issue remains: How do we robustly test the Copernican Principle independently of dark energy or theory of gravity?

@article{doi101016jcrhy201204005,
    author = "Clarkson, Chris",
    title = "Establishing homogeneity of the universe in the shadow of dark energy",
    year = "2012",
    journal = "Comptes Rendus Physique",
    abstract = "Assuming the universe is spatially homogeneous on the largest scales lays the foundation for almost all cosmology. This idea is based on the Copernican Principle, that we are not at a particularly special place in the universe. Surprisingly, this philosophical assumption has yet to be rigorously demonstrated independently of the standard paradigm. This issue has been brought to light by cosmological models which can potentially explain apparent acceleration by spatial inhomogeneity rather than dark energy. These models replace the temporal fine tuning associated with Λ with a spatial fine tuning, and so violate the Copernican assumption. While is seems unlikely that such models can really give a realistic solution to the dark energy problem, they do reveal how poorly constrained radial inhomogeneity actually is. So the bigger issue remains: How do we robustly test the Copernican Principle independently of dark energy or theory of gravity?",
    url = "https://doi.org/10.1016/j.crhy.2012.04.005",
    doi = "10.1016/j.crhy.2012.04.005",
    openalex = "W2046417303",
    references = "moffat2005cosmic"
}

Roger Penrose's groundbreaking and bestselling Road to Reality provided a comprehensive yet readable guide to our present understanding of the laws that are currently believed to govern our universe. In Cycles of Time, he moves far beyond this to develop a completely new perspective on cosmology, providing a quite unexpected answer to the often-asked question, 'what came before the Big Bang'? The two key ideas underlying this novel proposal are a penetrating analysis the Second Law of thermodynamics - according to which the 'randomness' of our world is continually increasing - and a thorough examination of the light-cone geometry of space-time. Penrose is able to combine these two central themes to show how the expected ultimate fate of our accelerating, expanding universe can actually be reinterpreted as the 'Big Bang' of a new one. On the way, many other basic ingredients are presented, and their roles discussed in detail, though without any complex mathematical formulae (these all being banished to the appendices). Various standard and non-standard cosmological models are presented, as is the fundamental and ubiquitous role of the cosmic microwave background. Also crucial to the discussion are the huge black holes lying in galactic centres, and their eventual disappearance via the mysterious process of Hawking evaporation.

@article{doi105860choice492636,
    title = "Cycles of time: an extraordinary new view of the universe",
    year = "2012",
    journal = "Choice Reviews Online",
    abstract = "Roger Penrose's groundbreaking and bestselling Road to Reality provided a comprehensive yet readable guide to our present understanding of the laws that are currently believed to govern our universe. In Cycles of Time, he moves far beyond this to develop a completely new perspective on cosmology, providing a quite unexpected answer to the often-asked question, 'what came before the Big Bang'? The two key ideas underlying this novel proposal are a penetrating analysis the Second Law of thermodynamics - according to which the 'randomness' of our world is continually increasing - and a thorough examination of the light-cone geometry of space-time. Penrose is able to combine these two central themes to show how the expected ultimate fate of our accelerating, expanding universe can actually be reinterpreted as the 'Big Bang' of a new one. On the way, many other basic ingredients are presented, and their roles discussed in detail, though without any complex mathematical formulae (these all being banished to the appendices). Various standard and non-standard cosmological models are presented, as is the fundamental and ubiquitous role of the cosmic microwave background. Also crucial to the discussion are the huge black holes lying in galactic centres, and their eventual disappearance via the mysterious process of Hawking evaporation.",
    url = "https://doi.org/10.5860/choice.49-2636",
    doi = "10.5860/choice.49-2636",
    openalex = "W1486184397"
}

This paper presents the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensing-potential power spectra. We find that the Planck spectra at high multipoles (> 40) are extremely well described by the standard spatiallyflat six-parameter CDM cosmology with a power-law spectrum of adiabatic scalar perturbations. Within the context of this cosmology, the Planck data determine the cosmological parameters to high precision: the angular size of the sound horizon at recombination, the physical densities of baryons and cold dark matter, and the scalar spectral index are estimated to be * = (1.04147 0.00062) 10 -2, b h 2 = 0.02205 0.00028, c h 2 = 0.1199 0.0027, and n s = 0.9603 0.0073, respectively (note that in this abstract we quote 68% errors on measured parameters and 95% upper limits on other parameters). For this cosmology, we find a low value of the Hubble constant, H 0 = (67.3 1.2) km s -1 Mpc -1, and a high value of the matter density parameter, m = 0.315 0.017. These values are in tension with recent direct measurements of H 0 and the magnituderedshift relation for Type Ia supernovae, but are in excellent agreement with geometrical constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent level precision using Planck CMB data alone. We use high-resolution CMB data together with Planck to provide greater control on extragalactic foreground components in an investigation of extensions to the six-parameter CDM model. We present selected results from a large grid of cosmological models, using a range of additional astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured over the standard six-parameter CDM cosmology. The deviation of the scalar spectral index from unity is insensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find an upper limit of r 0.002 < 0.11 on the tensor-to-scalar ratio. There is no evidence for additional neutrino-like relativistic particles beyond the three families of neutrinos in the standard model. Using BAO and CMB data, we find N eff = 3.30 0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the sum of neutrino masses. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of N eff = 3.046. We find no evidence for dynamical dark energy; using BAO and CMB data, the dark energy equation of state parameter is constrained to be w = -1.13 +0.13 -0.10. We also use the Planck data to set limits on a possible variation of the fine-structure constant, dark matter annihilation and primordial magnetic fields. Despite the success of the six-parameter CDM model in describing the Planck data at high multipoles, we note that this cosmology does not provide a good fit to the temperature power spectrum at low multipoles. The unusual shape of the spectrum in the multipole range 20 < < 40 was seen previously in the WMAP data and is a real feature of the primordial CMB anisotropies. The poor fit to the spectrum at low multipoles is not of decisive significance, but is an "anomaly" in an otherwise self-consistent analysis of the Planck temperature data.

@article{doi10105100046361201321591,
    author = "Ade, P. A. R. and Aghanim, N. and Armitage-Caplan, C. and Arnaud, M. and Ashdown, M. and Atrio‐Barandela, F. and Aumont, J. and Baccigalupi, C. and Banday, A. J. and Barreiro, R. B. and Bartlett, J. G. and Battaner, E. and Benabed, K. and Benoı̂t, A. and Benoit-Lévy, A. and Bernard, J. P. and Bersanelli, M. and Bielewicz, P. and Bobin, J. and Bock, J. J. and Bonaldi, A. and Bond, J. R. and Borrill, J. and Bouchet, F. R. and Bridges, M. and Bucher, M. and Burigana, C. and Butler, R. C. and Calabrese, E. and Cappellini, B. and Cardoso, J.-F. and Catalano, A. and Challinor, A. and Chamballu, A. and Chary, Ranga‐Ram and Chen, X. and Chiang, H. C. and Chiang, L.-Y and Christensen, P. R. and Church, S. and Clements, D. L. and Colombi, S. and Colombo, L. P. L. and Couchot, F. and Coulais, A. and Crill, B. P. and Curto, A. and Cuttaia, F. and Danese, L. and Davies, R. D. and Davis, R. J. and de Bernardis, P. and de Rosa, A. and de Zotti, G. and Delabrouille, J. and Delouis, J.‐M. and Désert, F.–X. and Dickinson, C. and Diego, J. M. and Dolag, K. and Dole, H. and Donzelli, S. and Doré, O. and Douspis, M. and Dunkley, J. and Dupac, X. and Efstathiou, G. and Elsner, F. and Enßlin, T. A. and Eriksen, H. K. and Finelli⋆, F. and Forni, O. and Frailis, M. and Fraisse, A. A. and Franceschi, E. and Gaier, T. and Galeotta, S. and Galli, S. and Ganga, K. and Giard, M. and Giardino, G. and Giraud–Héraud, Y. and Gjerløw, E. and González-Nuevo, J. and Górski, K. M. and Gratton, S. and Gregorio, A. and Gruppuso, A. and Gudmundsson, J. E. and Haïssinski, J. and Hamann, J. and Hansen, F. K. and Hanson, D. and Harrison, D. L. and Henrot–Versillé, S. and Hernández-Monteagudo, C. and Herranz, D. and Hildebrandt, S. R. and Hivon, E. and Hobson, M.",
    title = "Planck 2013 results. XVI. Cosmological parameters",
    year = "2014",
    journal = "Astronomy and Astrophysics",
    abstract = {This paper presents the first cosmological results based on Planck measurements of the cosmic microwave background (CMB) temperature and lensing-potential power spectra. We find that the Planck spectra at high multipoles (> 40) are extremely well described by the standard spatiallyflat six-parameter CDM cosmology with a power-law spectrum of adiabatic scalar perturbations. Within the context of this cosmology, the Planck data determine the cosmological parameters to high precision: the angular size of the sound horizon at recombination, the physical densities of baryons and cold dark matter, and the scalar spectral index are estimated to be * = (1.04147 0.00062) 10 -2, b h 2 = 0.02205 0.00028, c h 2 = 0.1199 0.0027, and n s = 0.9603 0.0073, respectively (note that in this abstract we quote 68\% errors on measured parameters and 95\% upper limits on other parameters). For this cosmology, we find a low value of the Hubble constant, H 0 = (67.3 1.2) km s -1 Mpc -1, and a high value of the matter density parameter, m = 0.315 0.017. These values are in tension with recent direct measurements of H 0 and the magnituderedshift relation for Type Ia supernovae, but are in excellent agreement with geometrical constraints from baryon acoustic oscillation (BAO) surveys. Including curvature, we find that the Universe is consistent with spatial flatness to percent level precision using Planck CMB data alone. We use high-resolution CMB data together with Planck to provide greater control on extragalactic foreground components in an investigation of extensions to the six-parameter CDM model. We present selected results from a large grid of cosmological models, using a range of additional astrophysical data sets in addition to Planck and high-resolution CMB data. None of these models are favoured over the standard six-parameter CDM cosmology. The deviation of the scalar spectral index from unity is insensitive to the addition of tensor modes and to changes in the matter content of the Universe. We find an upper limit of r 0.002 < 0.11 on the tensor-to-scalar ratio. There is no evidence for additional neutrino-like relativistic particles beyond the three families of neutrinos in the standard model. Using BAO and CMB data, we find N eff = 3.30 0.27 for the effective number of relativistic degrees of freedom, and an upper limit of 0.23 eV for the sum of neutrino masses. Our results are in excellent agreement with big bang nucleosynthesis and the standard value of N eff = 3.046. We find no evidence for dynamical dark energy; using BAO and CMB data, the dark energy equation of state parameter is constrained to be w = -1.13 +0.13 -0.10. We also use the Planck data to set limits on a possible variation of the fine-structure constant, dark matter annihilation and primordial magnetic fields. Despite the success of the six-parameter CDM model in describing the Planck data at high multipoles, we note that this cosmology does not provide a good fit to the temperature power spectrum at low multipoles. The unusual shape of the spectrum in the multipole range 20 < < 40 was seen previously in the WMAP data and is a real feature of the primordial CMB anisotropies. The poor fit to the spectrum at low multipoles is not of decisive significance, but is an "anomaly" in an otherwise self-consistent analysis of the Planck temperature data.},
    url = "https://doi.org/10.1051/0004-6361/201321591",
    doi = "10.1051/0004-6361/201321591",
    openalex = "W2139937287",
    references = "doi10100797835407435381, doi101086186504, doi101086309179, doi101086377226, doi1010880004637x7072916, doi10108800670049192218, doi101103physrevd23347, doi101103physrevd64123522, doi101103physrevd66103511, doi101111j13652966201119250x, doi1012942lrr20112, openalexw3100355343"
}

The article discusses the problem of interpretation of the universe as a whole in the context of the modern dialogue between science and religion. It is argued that the very possibility of cosmology and theology imply each other. Thus humanity becomes the central problem of the dialogue because of its ambivalent position in the universe as being an organic physical being on the one hand and the articulating consciousness of the whole universe, on the other hand. On the basis of asymmetry in relation between theology and cosmology a methodology of a theological treatment of cosmology is suggested as being based in the irreducible primacy of the event of living with respect to any possible representation of the universe. A phenomenological methodology of "deconstructing" the ideas about the universe is suggested with the aim to disclose the source of these ideas in human person.

@article{doi101751619971370201581439,
    author = "Nesteruk, Alexei V.",
    title = "The Sense of the Universe: towards a New Phenomenological Turn in the Dialogue between Cosmology and Theology",
    year = "2015",
    journal = "Journal of Siberian Federal University Humanities \& Social Sciences",
    abstract = {The article discusses the problem of interpretation of the universe as a whole in the context of the modern dialogue between science and religion. It is argued that the very possibility of cosmology and theology imply each other. Thus humanity becomes the central problem of the dialogue because of its ambivalent position in the universe as being an organic physical being on the one hand and the articulating consciousness of the whole universe, on the other hand. On the basis of asymmetry in relation between theology and cosmology a methodology of a theological treatment of cosmology is suggested as being based in the irreducible primacy of the event of living with respect to any possible representation of the universe. A phenomenological methodology of "deconstructing" the ideas about the universe is suggested with the aim to disclose the source of these ideas in human person.},
    url = "https://doi.org/10.17516/1997-1370-2015-8-1-4-39",
    doi = "10.17516/1997-1370-2015-8-1-4-39",
    openalex = "W2181303128",
    references = "openalexw1577727379"
}

Over recent decades, the role of torsion in gravity has been extensively investigated along the main direction of bringing gravity closer to its gauge formulation and incorporating spin in a geometric description. Here we review various torsional constructions, from teleparallel, to Einstein-Cartan, and metric-affine gauge theories, resulting in extending torsional gravity in the paradigm of f (T) gravity, where f (T) is an arbitrary function of the torsion scalar. Based on this theory, we further review the corresponding cosmological and astrophysical applications. In particular, we study cosmological solutions arising from f (T) gravity, both at the background and perturbation levels, in different eras along the cosmic expansion. The f (T) gravity construction can provide a theoretical interpretation of the late-time universe acceleration, alternative to a cosmological constant, and it can easily accommodate with the regular thermal expanding history including the radiation and cold dark matter dominated phases. Furthermore, if one traces back to very early times, for a certain class of f (T) models, a sufficiently long period of inflation can be achieved and hence can be investigated by cosmic microwave background observations-or, alternatively, the Big Bang singularity can be avoided at even earlier moments due to the appearance of non-singular bounces. Various observational constraints, especially the bounds coming from the large-scale structure data in the case of f (T) cosmology, as well as the behavior of gravitational waves, are described in detail. Moreover, the spherically symmetric and black hole solutions of the theory are reviewed. Additionally, we discuss various extensions of the f (T) paradigm. Finally, we consider the relation with other modified gravitational theories, such as those based on curvature, like f (R) gravity, trying to illuminate the subject of which formulation, or combination of formulations, might be more suitable for quantization ventures and cosmological applications.

@article{doi101088003448857910106901,
    author = "Cai, Yi-Fu and Capozzıello, Salvatore and Laurentis, Mariafelicia De and Saridakis, Emmanuel N.",
    title = "f (T) teleparallel gravity and cosmology",
    year = "2016",
    journal = "Reports on Progress in Physics",
    abstract = "Over recent decades, the role of torsion in gravity has been extensively investigated along the main direction of bringing gravity closer to its gauge formulation and incorporating spin in a geometric description. Here we review various torsional constructions, from teleparallel, to Einstein-Cartan, and metric-affine gauge theories, resulting in extending torsional gravity in the paradigm of f (T) gravity, where f (T) is an arbitrary function of the torsion scalar. Based on this theory, we further review the corresponding cosmological and astrophysical applications. In particular, we study cosmological solutions arising from f (T) gravity, both at the background and perturbation levels, in different eras along the cosmic expansion. The f (T) gravity construction can provide a theoretical interpretation of the late-time universe acceleration, alternative to a cosmological constant, and it can easily accommodate with the regular thermal expanding history including the radiation and cold dark matter dominated phases. Furthermore, if one traces back to very early times, for a certain class of f (T) models, a sufficiently long period of inflation can be achieved and hence can be investigated by cosmic microwave background observations-or, alternatively, the Big Bang singularity can be avoided at even earlier moments due to the appearance of non-singular bounces. Various observational constraints, especially the bounds coming from the large-scale structure data in the case of f (T) cosmology, as well as the behavior of gravitational waves, are described in detail. Moreover, the spherically symmetric and black hole solutions of the theory are reviewed. Additionally, we discuss various extensions of the f (T) paradigm. Finally, we consider the relation with other modified gravitational theories, such as those based on curvature, like f (R) gravity, trying to illuminate the subject of which formulation, or combination of formulations, might be more suitable for quantization ventures and cosmological applications.",
    url = "https://doi.org/10.1088/0034-4885/79/10/106901",
    doi = "10.1088/0034-4885/79/10/106901",
    openalex = "W2177433753",
    references = "doi101103physrevd16953, doi101103physrevd64123522, doi101103physrevd68023509, openalexw3098371892"
}

@article{piran2016cosmic,
    author = "Piran, Tsvi and Jimenez, Raul and Cuesta, Antonio J. and Simpson, Fergus and Verde, Licia",
    title = "Cosmic Explosions, Life in the Universe, and the Cosmological Constant",
    year = "2016",
    journal = "Physical Review Letters",
    url = "https://doi.org/10.1103/physrevlett.116.081301",
    doi = "10.1103/physrevlett.116.081301",
    number = "8",
    openalex = "W1893055178",
    volume = "116",
    references = "doi101086305673, doi101086425155, doi1010880004637x6911182, doi10108800319112382028, doi101103physrevd73023505, doi101103physrevlett113231102, doi101103physrevlett592607, doi101111j13652966200711909x, doi101111j13652966200814066x, doi101111j13652966200915191x"
}

The Nobel Prize winning confirmation in 1998 of the accelerated expansion of our Universe put into sharp focus the need of a consistent theoretical model to explain the origin of this acceleration. As a result over the past two decades there has been a huge theoretical and observational effort into improving our understanding of the Universe. The cosmological equations describing the dynamics of a homogeneous and isotropic Universe are systems of ordinary differential equations, and one of the most elegant ways these can be investigated is by casting them into the form of dynamical systems. This allows the use of powerful analytical and numerical methods to gain a quantitative understanding of the cosmological dynamics derived by the models under study. In this review we apply these techniques to cosmology. We begin with a brief introduction to dynamical systems, fixed points, linear stability theory, Lyapunov stability, centre manifold theory and more advanced topics relating to the global structure of the solutions. Using this machinery we then analyse a large number of cosmological models and show how the stability conditions allow them to be tightly constrained and even ruled out on purely theoretical grounds. We are also able to identify those models which deserve further in depth investigation through comparison with observational data. This review is a comprehensive and detailed study of dynamical systems applications to cosmological models focusing on the late-time behaviour of our Universe, and in particular on its accelerated expansion. In self contained sections we present a large number of models ranging from canonical and non-canonical scalar fields, interacting models and non-scalar field models through to modified gravity scenarios. Selected models are discussed in detail and interpreted in the context of late-time cosmology.

@article{openalexw3101462954,
    author = "Bahamonde, S and Boehmer, CG and Carloni, S and Copeland, EJ and Fang, W and Tamanini, N",
    title = "Dynamical systems applied to cosmology: dark energy and modified gravity",
    year = "2017",
    journal = "UCL Discovery (University College London)",
    abstract = "The Nobel Prize winning confirmation in 1998 of the accelerated expansion of our Universe put into sharp focus the need of a consistent theoretical model to explain the origin of this acceleration. As a result over the past two decades there has been a huge theoretical and observational effort into improving our understanding of the Universe. The cosmological equations describing the dynamics of a homogeneous and isotropic Universe are systems of ordinary differential equations, and one of the most elegant ways these can be investigated is by casting them into the form of dynamical systems. This allows the use of powerful analytical and numerical methods to gain a quantitative understanding of the cosmological dynamics derived by the models under study. In this review we apply these techniques to cosmology. We begin with a brief introduction to dynamical systems, fixed points, linear stability theory, Lyapunov stability, centre manifold theory and more advanced topics relating to the global structure of the solutions. Using this machinery we then analyse a large number of cosmological models and show how the stability conditions allow them to be tightly constrained and even ruled out on purely theoretical grounds. We are also able to identify those models which deserve further in depth investigation through comparison with observational data. This review is a comprehensive and detailed study of dynamical systems applications to cosmological models focusing on the late-time behaviour of our Universe, and in particular on its accelerated expansion. In self contained sections we present a large number of models ranging from canonical and non-canonical scalar fields, interacting models and non-scalar field models through to modified gravity scenarios. Selected models are discussed in detail and interpreted in the context of late-time cosmology.",
    openalex = "W3101462954",
    references = "doi101088026493812821213001"
}

We review recent developments and results in testing general relativity (GR) at cosmological scales. The subject has witnessed rapid growth during the last two decades with the aim of addressing the question of cosmic acceleration and the dark energy associated with it. However, with the advent of precision cosmology, it has also become a well-motivated endeavor by itself to test gravitational physics at cosmic scales. We overview cosmological probes of gravity, formalisms and parameterizations for testing deviations from GR at cosmological scales, selected modified gravity (MG) theories, gravitational screening mechanisms, and computer codes developed for these tests. We then provide summaries of recent cosmological constraints on MG parameters and selected MG models. We supplement these cosmological constraints with a summary of implications from the recent binary neutron star merger event. Next, we summarize some results on MG parameter forecasts with and without astrophysical systematics that will dominate the uncertainties. The review aims at providing an overall picture of the subject and an entry point to students and researchers interested in joining the field. It can also serve as a quick reference to recent results and constraints on testing gravity at cosmological scales.

@article{doi101007s4111401800174,
    author = "Ishak, Mustapha",
    title = "Testing general relativity in cosmology",
    year = "2018",
    journal = "Living Reviews in Relativity",
    abstract = "We review recent developments and results in testing general relativity (GR) at cosmological scales. The subject has witnessed rapid growth during the last two decades with the aim of addressing the question of cosmic acceleration and the dark energy associated with it. However, with the advent of precision cosmology, it has also become a well-motivated endeavor by itself to test gravitational physics at cosmic scales. We overview cosmological probes of gravity, formalisms and parameterizations for testing deviations from GR at cosmological scales, selected modified gravity (MG) theories, gravitational screening mechanisms, and computer codes developed for these tests. We then provide summaries of recent cosmological constraints on MG parameters and selected MG models. We supplement these cosmological constraints with a summary of implications from the recent binary neutron star merger event. Next, we summarize some results on MG parameter forecasts with and without astrophysical systematics that will dominate the uncertainties. The review aims at providing an overall picture of the subject and an entry point to students and researchers interested in joining the field. It can also serve as a quick reference to recent results and constraints on testing gravity at cosmological scales.",
    url = "https://doi.org/10.1007/s41114-018-0017-4",
    doi = "10.1007/s41114-018-0017-4",
    openalex = "W2809838409",
    references = "doi101007bf01332580, doi101112plmss242190"
}

Models of the very early universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code from the eagle collaboration, we investigate the effect of the cosmological constant on the formation of galaxies and stars. We simulate universes with values of the cosmological constant ranging from Λ = 0 to Λ0 ×300, where Λ0 is the value of the cosmological constant in our Universe. Because the global star formation rate in our Universe peaks at t = 3.5 Gyr, before the onset of accelerating expansion, increases in Λ of even an order of magnitude have only a small effect on the star formation history and efficiency of the universe. We use our simulations to predict the observed value of the cosmological constant, given a measure of the multiverse. Whether the cosmological constant is successfully predicted depends crucially on the measure. The impact of the cosmological constant on the formation of structure in the universe is not a sharp enough function of Λ to explain its observed value alone.

@article{doi101093mnrassty846,
    author = "Barnes, Luke A. and Elahi, Pascal J. and Salcido, Jaime and Bower, R. G. and Lewis, Geraint F. and Theuns, Tom and Schaller, Matthieu and Crain, Robert A. and Schaye, Joop",
    title = "Galaxy formation efficiency and the multiverse explanation of the cosmological constant with EAGLE simulations",
    year = "2018",
    journal = "Monthly Notices of the Royal Astronomical Society",
    abstract = "Models of the very early universe, including inflationary models, are argued to produce varying universe domains with different values of fundamental constants and cosmic parameters. Using the cosmological hydrodynamical simulation code from the eagle collaboration, we investigate the effect of the cosmological constant on the formation of galaxies and stars. We simulate universes with values of the cosmological constant ranging from Λ = 0 to Λ0 ×300, where Λ0 is the value of the cosmological constant in our Universe. Because the global star formation rate in our Universe peaks at t = 3.5 Gyr, before the onset of accelerating expansion, increases in Λ of even an order of magnitude have only a small effect on the star formation history and efficiency of the universe. We use our simulations to predict the observed value of the cosmological constant, given a measure of the multiverse. Whether the cosmological constant is successfully predicted depends crucially on the measure. The impact of the cosmological constant on the formation of structure in the universe is not a sharp enough function of Λ to explain its observed value alone.",
    url = "https://doi.org/10.1093/mnras/sty846",
    doi = "10.1093/mnras/sty846",
    openalex = "W2784500484",
    references = "doi1010179781316661413, piran2016cosmic"
}

ABSTRACT We present a measurement of the Hubble constant (H0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analysed blindly with respect to the cosmological parameters. In a flat Λ cold dark matter (ΛCDM) cosmology, we find $H_{0} = 73.3_{-1.8}^{+1.7}~\mathrm{km~s^{-1}~Mpc^{-1}}$, a $2.4{{\ \rm per\ cent}}$ precision measurement, in agreement with local measurements of H0 from type Ia supernovae calibrated by the distance ladder, but in 3.1σ tension with Planck observations of the cosmic microwave background (CMB). This method is completely independent of both the supernovae and CMB analyses. A combination of time-delay cosmography and the distance ladder results is in 5.3σ tension with Planck CMB determinations of H0 in flat ΛCDM. We compute Bayes factors to verify that all lenses give statistically consistent results, showing that we are not underestimating our uncertainties and are able to control our systematics. We explore extensions to flat ΛCDM using constraints from time-delay cosmography alone, as well as combinations with other cosmological probes, including CMB observations from Planck, baryon acoustic oscillations, and type Ia supernovae. Time-delay cosmography improves the precision of the other probes, demonstrating the strong complementarity. Allowing for spatial curvature does not resolve the tension with Planck. Using the distance constraints from time-delay cosmography to anchor the type Ia supernova distance scale, we reduce the sensitivity of our H0 inference to cosmological model assumptions. For six different cosmological models, our combined inference on H0 ranges from ∼73 to 78 km s−1 Mpc−1, which is consistent with the local distance ladder constraints.

@article{doi101093mnrasstz3094,
    author = "Wong, Kenneth C. and Suyu, S. H. and Chen, Geoff C.-F. and Rusu, Cristian E. and Millon, Martin and Sluse, Dominique and Bonvin, V. and Fassnacht, C. D. and Taubenberger, S. and Auger, Matthew W. and Birrer, Simon and Chan, J. H. H. and Courbin, F. and Hilbert, Stefan and Tihhonova, O. and Treu, Tommaso and Agnello, Adriano and Ding, Xuheng and Jee, Inh and Komatsu, Eiichiro and Shajib, Anowar J. and Sonnenfeld, Alessandro and Blandford, R. D. and Koopmans, L. V. E. and Marshall, Philip J. and Meylan, Georges",
    title = "H0LiCOW – XIII. A 2.4 per cent measurement of H0 from lensed quasars: 5.3σ tension between early- and late-Universe probes",
    year = "2019",
    journal = "Monthly Notices of the Royal Astronomical Society",
    abstract = "ABSTRACT We present a measurement of the Hubble constant (H0) and other cosmological parameters from a joint analysis of six gravitationally lensed quasars with measured time delays. All lenses except the first are analysed blindly with respect to the cosmological parameters. In a flat Λ cold dark matter (ΛCDM) cosmology, we find $H\_{0} = 73.3\_{-1.8}^{+1.7}\textasciitilde \mathrm{km\textasciitilde s^{-1}\textasciitilde Mpc^{-1}}$, a $2.4{{\ \rm per\ cent}}$ precision measurement, in agreement with local measurements of H0 from type Ia supernovae calibrated by the distance ladder, but in 3.1σ tension with Planck observations of the cosmic microwave background (CMB). This method is completely independent of both the supernovae and CMB analyses. A combination of time-delay cosmography and the distance ladder results is in 5.3σ tension with Planck CMB determinations of H0 in flat ΛCDM. We compute Bayes factors to verify that all lenses give statistically consistent results, showing that we are not underestimating our uncertainties and are able to control our systematics. We explore extensions to flat ΛCDM using constraints from time-delay cosmography alone, as well as combinations with other cosmological probes, including CMB observations from Planck, baryon acoustic oscillations, and type Ia supernovae. Time-delay cosmography improves the precision of the other probes, demonstrating the strong complementarity. Allowing for spatial curvature does not resolve the tension with Planck. Using the distance constraints from time-delay cosmography to anchor the type Ia supernova distance scale, we reduce the sensitivity of our H0 inference to cosmological model assumptions. For six different cosmological models, our combined inference on H0 ranges from ∼73 to 78 km s−1 Mpc−1, which is consistent with the local distance ladder constraints.",
    url = "https://doi.org/10.1093/mnras/stz3094",
    doi = "10.1093/mnras/stz3094",
    openalex = "W2961457169",
    references = "doi10384715384357aab9bb"
}

Abstract We present a full-fledged analysis of Brans–Dicke cosmology with a cosmological constant and cold dark matter (BD-ΛCDM for short). We extend the scenarios where the current cosmological value of the BD-field is restricted by the local astrophysical domain to scenarios where that value is fixed only by the cosmological observations, which should be more natural in view of the possible existence of local screening mechanism. Our analysis includes both the background and perturbations equations in different gauges. We find that the BD-ΛCDM is favored by the overall cosmological data as compared to the concordance GR-ΛCDM model, namely data on distant supernovae, cosmic chronometers, local measurements of the Hubble parameter, baryonic acoustic oscillations, large-scale structure formation and the cosmic microwave background under full Planck 2018 CMB likelihood. We also test the impact of strong and weak-lensing data on our results, which can be significant. We find that the BD-ΛCDM can mimic effective quintessence with a significance of about 3.0–3.5 σ c.l. (depending on the lensing datasets). The fact that the BD-ΛCDM behaves effectively as a running vacuum model (RVM) when viewed from the GR perspective helps to alleviate some of the existing tensions with the data, such as the σ 8 excess predicted by GR-ΛCDM. On the other hand, the BD-ΛCDM model has a crucial bearing on the acute H 0 -tension with the local measurements, which is rendered virtually harmless owing to the small increase of the effective value of the gravitational constant with the expansion. The simultaneous alleviation of the two tensions is a most remarkable feature of BD-gravity with a cosmological constant in the light of the current observations, and hence goes in support of BD-ΛCDM against GR-ΛCDM.

@article{doi10108813616382abbc43,
    author = "Peracaula, Joan Solà and Gómez-Valent, Adrià and de Cruz Pérez, Javier and Moreno-Pulido, Cristian",
    title = "Brans–Dicke cosmology with a Λ-term: a possible solution to ΛCDM tensions*",
    year = "2020",
    journal = "Classical and Quantum Gravity",
    abstract = "Abstract We present a full-fledged analysis of Brans–Dicke cosmology with a cosmological constant and cold dark matter (BD-ΛCDM for short). We extend the scenarios where the current cosmological value of the BD-field is restricted by the local astrophysical domain to scenarios where that value is fixed only by the cosmological observations, which should be more natural in view of the possible existence of local screening mechanism. Our analysis includes both the background and perturbations equations in different gauges. We find that the BD-ΛCDM is favored by the overall cosmological data as compared to the concordance GR-ΛCDM model, namely data on distant supernovae, cosmic chronometers, local measurements of the Hubble parameter, baryonic acoustic oscillations, large-scale structure formation and the cosmic microwave background under full Planck 2018 CMB likelihood. We also test the impact of strong and weak-lensing data on our results, which can be significant. We find that the BD-ΛCDM can mimic effective quintessence with a significance of about 3.0–3.5 σ c.l. (depending on the lensing datasets). The fact that the BD-ΛCDM behaves effectively as a running vacuum model (RVM) when viewed from the GR perspective helps to alleviate some of the existing tensions with the data, such as the σ 8 excess predicted by GR-ΛCDM. On the other hand, the BD-ΛCDM model has a crucial bearing on the acute H 0 -tension with the local measurements, which is rendered virtually harmless owing to the small increase of the effective value of the gravitational constant with the expansion. The simultaneous alleviation of the two tensions is a most remarkable feature of BD-gravity with a cosmological constant in the light of the current observations, and hence goes in support of BD-ΛCDM against GR-ΛCDM.",
    url = "https://doi.org/10.1088/1361-6382/abbc43",
    doi = "10.1088/1361-6382/abbc43",
    openalex = "W3034121481",
    references = "doi101016jphysrep201809001"
}

We present the cosmological implications from final measurements of clustering using galaxies, quasars, and $\mathrm{Ly}\ensuremath{\alpha}$ forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, ${r}_{d}$, from eight different samples and six measurements of the growth rate parameter, $f{\ensuremath{\sigma}}_{8}$, from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization, under the same model, the BAO data provide nearly an order of magnitude improvement on curvature constraints relative to primary CMB constraints alone. Independent of distance measurements, the SDSS RSD data complement weak lensing measurements from the Dark Energy Survey (DES) in demonstrating a preference for a flat $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ cosmological model when combined with Planck measurements. The combined BAO and RSD measurements indicate ${\ensuremath{\sigma}}_{8}=0.85\ifmmode\pm\else\textpm\fi{}0.03$, implying a growth rate that is consistent with predictions from Planck temperature and polarization data and with General Relativity. When combining the results of SDSS BAO and RSD, Planck, Pantheon Type Ia supernovae (SNe Ia), and DES weak lensing and clustering measurements, all multiple-parameter extensions remain consistent with a $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. Regardless of cosmological model, the precision on each of the three parameters, ${\mathrm{\ensuremath{\Omega}}}_{\mathrm{\ensuremath{\Lambda}}}$, ${H}_{0}$, and ${\ensuremath{\sigma}}_{8}$, remains at roughly 1%, showing changes of less than 0.6% in the central values between models. In a model that allows for free curvature and a time-evolving equation of state for dark energy, the combined samples produce a constraint ${\mathrm{\ensuremath{\Omega}}}_{k}=\ensuremath{-}0.0022\ifmmode\pm\else\textpm\fi{}0.0022$. The dark energy constraints lead to ${w}_{0}=\ensuremath{-}0.909\ifmmode\pm\else\textpm\fi{}0.081$ and ${w}_{a}=\ensuremath{-}0.4{9}_{\ensuremath{-}0.30}^{+0.35}$, corresponding to an equation of state of ${w}_{p}=\ensuremath{-}1.018\ifmmode\pm\else\textpm\fi{}0.032$ at a pivot redshift ${z}_{p}=0.29$ and a Dark Energy Task Force Figure of Merit of 94. The inverse distance ladder measurement under this model yields ${H}_{0}=68.18\ifmmode\pm\else\textpm\fi{}0.79\text{}\text{}\mathrm{km}\text{}{\mathrm{s}}^{\ensuremath{-}1}\text{}{\mathrm{Mpc}}^{\ensuremath{-}1}$, remaining in tension with several direct determination methods; the BAO data allow Hubble constant estimates that are robust against the assumption of the cosmological model. In addition, the BAO data allow estimates of ${H}_{0}$ that are independent of the CMB data, with similar central values and precision under a $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. Our most constraining combination of data gives the upper limit on the sum of neutrino masses at $\ensuremath{\sum}{m}_{\ensuremath{\nu}}<0.115\text{}\text{}\mathrm{eV}$ (95% confidence). Finally, we consider the improvements in cosmology constraints over the last decade by comparing our results to a sample representative of the period 2000--2010. We compute the relative gain across the five dimensions spanned by $w$, ${\mathrm{\ensuremath{\Omega}}}_{k}$, $\ensuremath{\sum}{m}_{\ensuremath{\nu}}$, ${H}_{0}$, and ${\ensuremath{\sigma}}_{8}$ and find that the SDSS BAO and RSD data reduce the total posterior volume by a factor of 40 relative to the previous generation. Adding again the Planck, DES, and Pantheon SN Ia samples leads to an overall contraction in the five-dimensional posterior volume of 3 orders of magnitude.

@article{doi101103physrevd103083533,
    author = "Alam, Shadab and Aubert, M and Àvila, S. and Balland, Christophe and Bautista, Julian and Bershady, Matthew A. and Bizyaev, Dmitry and Blanton, Michael R. and Bolton, A. and Bovy, Jo and Brinkmann, J. and Brownstein, Joel R. and Burtin, E. and Chabanier, Solène and Chapman, Michael J. and Choi, Peter Doohyun and Chuang, Chia-Hsun and Comparat, Johan and Cousinou, Marie-Claude and Cuceu, Andrei and Dawson, Kyle and de la Torre, Sylvain and de Mattia, Arnaud and de Sainte Agathe, Victoria and du Mas des Bourboux, Hélion and Escoffier, S. and Etourneau, Thomas and Farr, James R. and Font-Ribera, Andreu and Frinchaboy, Peter M. and Fromenteau, S. and Gil-Marín, Héctor and Goff, Jean-Marc Le and Gonzalez-Morales, Alma X. and González-Pérez, Violeta and Grabowski, Kathleen and Guy, Julien and Hawken, A. J. and Hou, Jiamin and Kong, Hui and Parker, J.R. and Klaene, Mark A. and Kneib, Jean‐Paul and Lin, S. Y. and Long, Daniel W. and Lyke, Brad W. and de la Macorra, Axel and Martini, Paul and Masters, Karen L. and Mohammad, Faizan G and Moon, Jeongin and Mueller, Eva-Maria and Muñoz-Gutiérrez, A. and Myers, Adam D. and Nadathur, S. and Neveux, Richard and Newman, Jeffrey A. and Noterdaeme, P. and Oravetz, Audrey and Oravetz, Daniel and Palanque‐Delabrouille, N. and Pan, Kaike and Paviot, Romain and Percival, Will J. and Pérez-Ràfols, Ignasi and Petitjean, Patrick and Pieri, Matthew M. and Prakash, Abhishek and Raichoor, Anand and Ravoux, C. and Rezaie, Mehdi and Rich, James and Ross, Ashley J. and Rossi, Graziano and Ruggeri, Rossana and Ruhlmann-Kleider, V. and Sánchez, Ariel G. and Sánchez, Javier and Sánchez-Gallego, José and Sayres, Conor and Schneider, Donald P. and Seo, Hee‐Jong and Shafieloo, Arman and Slosar, Anže and Smith, A. G. and Stermer, Julianna and Tamone, Amélie and Tinker, Jeremy L. and Tojeiro, Rita and Vargas-Magaña, M. and Variu, Andrei and Wang, Yuting and Weaver, Benjamin Alan and Weijmans, Anne-Marie and Yèche, Christophe and Zarrouk, Pauline and Zhao, Cheng and Zhao, Gong‐Bo and Zheng, Zheng",
    title = "Completed SDSS-IV extended Baryon Oscillation Spectroscopic Survey: Cosmological implications from two decades of spectroscopic surveys at the Apache Point Observatory",
    year = "2021",
    journal = "Physical review. D/Physical review. D.",
    abstract = "We present the cosmological implications from final measurements of clustering using galaxies, quasars, and $\mathrm{Ly}\ensuremath{\alpha}$ forests from the completed Sloan Digital Sky Survey (SDSS) lineage of experiments in large-scale structure. These experiments, composed of data from SDSS, SDSS-II, BOSS, and eBOSS, offer independent measurements of baryon acoustic oscillation (BAO) measurements of angular-diameter distances and Hubble distances relative to the sound horizon, ${r}\_{d}$, from eight different samples and six measurements of the growth rate parameter, $f{\ensuremath{\sigma}}\_{8}$, from redshift-space distortions (RSD). This composite sample is the most constraining of its kind and allows us to perform a comprehensive assessment of the cosmological model after two decades of dedicated spectroscopic observation. We show that the BAO data alone are able to rule out dark-energy-free models at more than eight standard deviations in an extension to the flat, $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model that allows for curvature. When combined with Planck Cosmic Microwave Background (CMB) measurements of temperature and polarization, under the same model, the BAO data provide nearly an order of magnitude improvement on curvature constraints relative to primary CMB constraints alone. Independent of distance measurements, the SDSS RSD data complement weak lensing measurements from the Dark Energy Survey (DES) in demonstrating a preference for a flat $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ cosmological model when combined with Planck measurements. The combined BAO and RSD measurements indicate ${\ensuremath{\sigma}}\_{8}=0.85\ifmmode\pm\else\textpm\fi{}0.03$, implying a growth rate that is consistent with predictions from Planck temperature and polarization data and with General Relativity. When combining the results of SDSS BAO and RSD, Planck, Pantheon Type Ia supernovae (SNe Ia), and DES weak lensing and clustering measurements, all multiple-parameter extensions remain consistent with a $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. Regardless of cosmological model, the precision on each of the three parameters, ${\mathrm{\ensuremath{\Omega}}}\_{\mathrm{\ensuremath{\Lambda}}}$, ${H}\_{0}$, and ${\ensuremath{\sigma}}\_{8}$, remains at roughly 1\%, showing changes of less than 0.6\% in the central values between models. In a model that allows for free curvature and a time-evolving equation of state for dark energy, the combined samples produce a constraint ${\mathrm{\ensuremath{\Omega}}}\_{k}=\ensuremath{-}0.0022\ifmmode\pm\else\textpm\fi{}0.0022$. The dark energy constraints lead to ${w}\_{0}=\ensuremath{-}0.909\ifmmode\pm\else\textpm\fi{}0.081$ and ${w}\_{a}=\ensuremath{-}0.4{9}\_{\ensuremath{-}0.30}^{+0.35}$, corresponding to an equation of state of ${w}\_{p}=\ensuremath{-}1.018\ifmmode\pm\else\textpm\fi{}0.032$ at a pivot redshift ${z}\_{p}=0.29$ and a Dark Energy Task Force Figure of Merit of 94. The inverse distance ladder measurement under this model yields ${H}\_{0}=68.18\ifmmode\pm\else\textpm\fi{}0.79\text{}\text{}\mathrm{km}\text{}{\mathrm{s}}^{\ensuremath{-}1}\text{}{\mathrm{Mpc}}^{\ensuremath{-}1}$, remaining in tension with several direct determination methods; the BAO data allow Hubble constant estimates that are robust against the assumption of the cosmological model. In addition, the BAO data allow estimates of ${H}\_{0}$ that are independent of the CMB data, with similar central values and precision under a $\mathrm{\ensuremath{\Lambda}}\mathrm{CDM}$ model. Our most constraining combination of data gives the upper limit on the sum of neutrino masses at $\ensuremath{\sum}{m}\_{\ensuremath{\nu}}<0.115\text{}\text{}\mathrm{eV}$ (95\% confidence). Finally, we consider the improvements in cosmology constraints over the last decade by comparing our results to a sample representative of the period 2000--2010. We compute the relative gain across the five dimensions spanned by $w$, ${\mathrm{\ensuremath{\Omega}}}\_{k}$, $\ensuremath{\sum}{m}\_{\ensuremath{\nu}}$, ${H}\_{0}$, and ${\ensuremath{\sigma}}\_{8}$ and find that the SDSS BAO and RSD data reduce the total posterior volume by a factor of 40 relative to the previous generation. Adding again the Planck, DES, and Pantheon SN Ia samples leads to an overall contraction in the five-dimensional posterior volume of 3 orders of magnitude.",
    url = "https://doi.org/10.1103/physrevd.103.083533",
    doi = "10.1103/physrevd.103.083533",
    openalex = "W3043102132",
    references = "doi10105100046361201833910, doi101093mnrasstx721, doi10384715384357aab9bb"
}

@misc{crossref2022universe,
    title = "universe, including Cosmology",
    year = "2022",
    booktitle = "Shakespeare and Science",
    url = "https://doi.org/10.5040/9781350044654.art249",
    doi = "10.5040/9781350044654.art249",
    openalex = "W4402224560",
    pages = "237-238"
}

The standard Λ Cold Dark Matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H0, the σ8–S8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements. After showing the H0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Ωm, and the amplitude or rate of the growth of structure (σ8,fσ8). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H0–S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions.

@misc{doi101016jjheap202204002,
    author = "Abdalla, Élcio and Abellán, Guillermo Franco and Aboubrahim, Amin and Agnello, Adriano and Akarsu, Özgür and Akrami, Y. and Alestas, George and Aloni, Daniel and Amendola, Luca and Anchordoqui, Luis A. and Anderson, Richard I. and Arendse, Nikki and Asgari, Marika and Ballardini, M. and Barger, V. and Basilakos, Spyros and Batista, Ronaldo C. and Battistelli, E. S. and Battye, Richard A. and Benetti, Micol and Benisty, David and Berlin, Asher and de Bernardis, P. and Berti, Emanuele and Bidenko, Bohdan and Birrer, Simon and Blakeslee, John P. and Boddy, Kimberly K. and Bom, Clécio R. and Bonilla, Alexander and Borghi, Nicola and Bouchet, F. R. and Braglia, Matteo and Buchert, Thomas and Buckley‐Geer, E. and Calabrese, Erminia and Caldwell, Robert R. and Camarena, David and Capozzıello, Salvatore and Casertano, Stefano and Chen, Geoff C.-F. and Chluba, Jens and Chen, Angela and Chen, Hsin-Yu and Chudaykin, Anton and Cicoli, Michele and Copi, Craig J. and Courbin, F. and Cyr-Racine, Francis-Yan and Czerny, B. and Dainotti, Maria Giovanna and D’Amico, Guido and Davis, Anne-Christine and de Cruz Pérez, Javier and de Haro, Jaume and Delabrouille, Jacques and Denton, Peter B. and Dhawan, Suhail and Dienes, Keith R. and Valentino, Eleonora Di and Du, Pu and Eckert, D. and Escamilla‐Rivera, Celia and Ferté, A. and Finelli⋆, F. and Fosalba, P. and Freedman, Wendy L. and Frusciante, Noemi and Gaztañaga, E. and Giarè, William and Giusarma, Elena and Gómez-Valent, Adrià and Handley, Will and Harrison, I. and Hart, Luke and Hazra, Dhiraj Kumar and Heavens, Alan and Heinesen, Asta and Hildebrandt, H. and Hill, J. Colin and Hogg, Natalie B and Holz, D. E. and Hooper, Deanna C. and Hosseininejad, Nikoo and Huterer, Dragan and Ishak, Mustapha and Ivanov, Mikhail M. and Jaffe, Andrew H. and Jang, In Sung and Jedamzik, Karsten and Jiménez, Raúl and Joseph, Melissa and Joudaki, Shahab and Kamionkowski, Marc and Karwal, Tanvi and Kazantzidis, Lavrentios and Keeley, Ryan E. and Klasen, Michael and Komatsu, Eiichiro and Koopmans, L. V. E.",
    title = "Cosmology intertwined: A review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies",
    year = "2022",
    booktitle = "Archivio istituzionale della ricerca (Alma Mater Studiorum Università di Bologna)",
    abstract = "The standard Λ Cold Dark Matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H0, the σ8–S8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements. After showing the H0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Ωm, and the amplitude or rate of the growth of structure (σ8,fσ8). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H0–S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions.",
    url = "https://doi.org/10.1016/j.jheap.2022.04.002",
    doi = "10.1016/j.jheap.2022.04.002",
    openalex = "W4225610241",
    references = "doi10105100046361201833910, doi10108802649381159013, doi10108811266708200006006, doi101103physrevd80122003, doi1012942lrr20112, doi10384715384357aab9bb"
}

Abstract We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω M = 0.334 ± 0.018 from SNe Ia alone. For a flat w 0 CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s −1 Mpc −1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 0.978 − 0.031 + 0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 73.3 ± 1.1 km s −1 Mpc −1 when including SH0ES Cepheid distances, and w a = − 0.65 − 0.32 + 0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.

@article{doi10384715384357ac8e04,
    author = "Brout, Dillon and Scolnic, D. and Popovic, B and Riess, Adam G. and Carr, Anthony and Zuntz, Joe and Kessler, Rick and Davis, T. M. and Hinton, S. R. and Jones, D. O. and Kenworthy, W. D. and Peterson, Erik R. and Said, Khaled and Taylor, G. and Ali, Noor and Armstrong, P. and Charvu, Pranav and Dwomoh, Arianna and Meldorf, Cole and Palmese, A. and Qu, Helen and Rose, Benjamin and Sánchez, B. and Stubbs, C. W. and Vincenzi, M. and Wood, Charlotte M. and Brown, P. J. and Chen, R and Chambers, K. C. and Coulter, D. A. and Dai, Mi and Dimitriadis, G. and Filippenko, A. V. and Foley, R. J. and Jha, Saurabh W. and Kelsey, L and Kirshner, R. and Möller, A. and Muir, J. and Nadathur, S. and Pan, Y. C. and Rest, A. and Rojas-Bravo, C. and Šako, M. and Siebert, M. R. and Smith, M. and Stahl, Benjamin E. and Wiseman, Phil",
    title = "The Pantheon+ Analysis: Cosmological Constraints",
    year = "2022",
    journal = "The Astrophysical Journal",
    abstract = "Abstract We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find Ω M = 0.334 ± 0.018 from SNe Ia alone. For a flat w 0 CDM model, we measure w 0 = −0.90 ± 0.14 from SNe Ia alone, H 0 = 73.5 ± 1.1 km s −1 Mpc −1 when including the Cepheid host distances and covariance (SH0ES), and w 0 = − 0.978 − 0.031 + 0.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w 0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w 0 w a CDM universe, and measure w a = − 0.1 − 2.0 + 0.9 from Pantheon+ SNe Ia alone, H 0 = 73.3 ± 1.1 km s −1 Mpc −1 when including SH0ES Cepheid distances, and w a = − 0.65 − 0.32 + 0.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H 0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.",
    url = "https://doi.org/10.3847/1538-4357/ac8e04",
    doi = "10.3847/1538-4357/ac8e04",
    openalex = "W4282961335",
    references = "doi10105100046361201833910, doi10384715384357aab9bb"
}

@article{luu2023axionhiggs,
    author = "Luu, Hoang Nhan",
    title = "Axion-Higgs cosmology: Cosmic microwave background and cosmological tensions",
    year = "2023",
    journal = "Physical Review D",
    url = "https://doi.org/10.1103/physrevd.107.023513",
    doi = "10.1103/physrevd.107.023513",
    number = "2",
    openalex = "W4313991527",
    volume = "107",
    references = "doi101016jphysrep201606005, doi10105100046361201833910, doi101086309179, doi10108813616382ac086d, doi101093mnrasstv154, doi101093mnrasstx721, doi101103physrevd66103511, doi101111j13652966201119250x, doi10384715384357aab9bb, doi10384715384357ab1422"
}

Cosmological scalar fields coupled to the Standard Model drive temporal variations in the fundamental constants that grow with redshift, positioning the early Universe as a powerful tool to study such models. We investigate the dynamics and phenomenology of coupled scalars from the early Universe to the present to consistently leverage the myriad searches for time-varying constants and the cosmological signatures of scalars’ gravitational effects. We compute the in-medium contribution from Standard Model particles to the scalar’s dynamics and identify only a limited range of couplings for which the scalar has an observable impact on the fundamental constants without either evolving before recombination or gravitating non-negligibly. We then extend existing laboratory and astrophysical bounds to the hyperlight scalar regime. We present joint limits from the early and late Universe, specializing to hyperlight, quadratically coupled scalars that modulate the mass of the electron or the strength of electromagnetism and make up a subcomponent of the dark matter today. Our dedicated analysis of observations of the cosmic microwave background, baryon acoustic oscillations, and type Ia supernovae provides the most stringent constraints on quadratically coupled scalars with masses from 10 − 28.5 to ∼ 10 − 31 eV, below which quasar absorption spectra yield stronger bounds. These results jointly limit hyperlight scalars that comprise a few percent of the current dark matter density to near- or subgravitational couplings to electrons or photons.

@article{doi101103pylsgvyr,
    author = "Baryakhtar, Masha and Simon, Olivier and Weiner, Zachary J.",
    title = "Searching for coupled, hyperlight scalars across cosmic history",
    year = "2025",
    journal = "Physical review. D/Physical review. D.",
    abstract = "Cosmological scalar fields coupled to the Standard Model drive temporal variations in the fundamental constants that grow with redshift, positioning the early Universe as a powerful tool to study such models. We investigate the dynamics and phenomenology of coupled scalars from the early Universe to the present to consistently leverage the myriad searches for time-varying constants and the cosmological signatures of scalars’ gravitational effects. We compute the in-medium contribution from Standard Model particles to the scalar’s dynamics and identify only a limited range of couplings for which the scalar has an observable impact on the fundamental constants without either evolving before recombination or gravitating non-negligibly. We then extend existing laboratory and astrophysical bounds to the hyperlight scalar regime. We present joint limits from the early and late Universe, specializing to hyperlight, quadratically coupled scalars that modulate the mass of the electron or the strength of electromagnetism and make up a subcomponent of the dark matter today. Our dedicated analysis of observations of the cosmic microwave background, baryon acoustic oscillations, and type Ia supernovae provides the most stringent constraints on quadratically coupled scalars with masses from 10 − 28.5 to ∼ 10 − 31 eV, below which quasar absorption spectra yield stronger bounds. These results jointly limit hyperlight scalars that comprise a few percent of the current dark matter density to near- or subgravitational couplings to electrons or photons.",
    url = "https://doi.org/10.1103/pyls-gvyr",
    doi = "10.1103/pyls-gvyr",
    openalex = "W4410549979",
    references = "luu2023axionhiggs"
}

MU4D VIDEO - G.SALDUCCI NOUVEAU LOGO EN PDF ( Logiciel Blender ) / NEW LOGO IN PDF ( Blender Software ) 4DUM 4-Dimensional Universal Matrix : The Fundamental axiom of reality (English version)New Cosmological ModelGérald SALDUCCI - Introduction The 4DUM cosmological model proposes an innovative vision of the fundamental structure of space-time and the resulting dynamics of matter. Unlike the standard ΛCDM model, often perceived as centered on the nature of the universe from our observational point of view, an approach that can be called "geocentric," 4DUM adopts a conceptual "heliocentric" perspective aiming to transcend this established framework, which I consider limiting the global understanding of the universe. By breaking these conceptual limits, 4DUM fits into a more universal approach based on a space-time matrix defined as a primordial quantum substrate, infinite, isotropic, and flat, without boundaries or edges. It is consequently the source of primordial energy and matter, generated by fluctuations of quantum vacuum energy, and possibly by more hypothetical singularities such as white fountains causing local metric deformations, giving rise to so-called "bubble universes." Space being the manifestation of time, this conceptual approach offers a strong ontology of space-time as absolute. - Context Standard cosmological model ΛCDM rely on an initial singularity (Big Bang) and a defined topology of the universe, conceptually incorporating the fabric of space-time and matter into a single singularity before the Big Bang, contrary to my model which proposes an alternative, considering an omnipotent space-time without beginning or end. This matrix is flat, isotropic, infinite, and borderless, thus without global topology.4DUM aims to unify quantum physics, special relativity, and general relativity based on this conceptual decoupling between space-time and matter, the latter emerging either through the Casimir effect resulting from quantum vacuum fluctuations or through the possible presence of a singularity from a white fountain (white hole). - Model Description a) The space-time matrix: The 4DUM is a fundamental fabric or a dense mesh of space-time quanta.It is isotropic and flat in all directions, ensuring homogeneity and the absence of overall curvature.It is infinite and boundaryless, meaning it has neither spatial limits nor borders.In this Matrix, space is the manifestation of time. b) Generation of energy and matter: Primordial energy is produced by the creation of "+ and - pairs" via the Casimir effect linked to quantum vacuum fluctuations. These particles, accumulating, form a pocket in the matrix where this extremely concentrated primordial energy creates a plasma which, beyond a critical threshold, can exhibit the dynamics of a white fountain expelling this primordial matter, thus forming a "bubble universe" post-Big Bang, releasing its own kinetic energy.This primordial energy transforms into matter through thermal dissipation.It is also possible that phenomena such as white fountains (white holes) locally generate deformations of the matrix, thus forming "bubble universes." c) Bubble universes and local deformations: These "bubble universes" are envisioned as local deformations of the metric within the Matrix, characterized by a distinct metric.They could be connected by Einstein-Rosen bridges (wormholes), forming a complex network comparable to a neural network. - Temporal Duality The model proposes a temporal duality : - A global absolute time associated with the matrix, stable and uniform.- A local relative time in the "bubble universes," resulting from metric deformations.This duality reconciles a universal fundamental time with variable local times, integrating aspects of relativity and quantum mechanics. - Conceptual Ontology 4DUM does not limit itself to a phenomenological description or simple mathematical modeling but proposes a fundamental and structuring nature of cosmic reality. This strong ontology rests on several pillars: Primordial Quantum Substrate :Space-time is conceived as a 4-Dimensional Universal Matrix, a fundamental quantum substrate, infinite, isotropic, and flat, without boundaries or edges. This matrix is the primary reality, the framework upon which everything is constructed. Dissociation between Space-Time and Matter :Contrary to the ΛCDM model where space-time and matter are intimately linked from the origin (Big Bang), 4DUM dissociates these two entities. Matter emerges from quantum fluctuations of this matrix, notably via the Casimir effect, or from hypothetical singularities such as white fountains. Bubble Universes as Local Deformations :Bubble universes are local manifestations of metric deformations in this matrix, each potentially possessing its own physical and temporal properties, forming a complex network. Conceptual Heliocentric Perspective :Opposed to a view centered on our observation point (geocentric), 4DUM proposes a more universal and global vision, seeking to transcend the conceptual limits of the standard model. - Implications and Perspectives Offers a new perspective on the nature of space-time and matter creation. Proposes a possible unification of major physical theories. Opens the way to testable predictions via the study of bubble universes and Einstein-Rosen bridges. Conclusion : This new model is an ambitious proposal aiming to rethink the fundamental structure of the universe. By combining an infinite primordial quantum substrate with potential local deformations, it offers a unifying and innovative framework for modern cosmology. "Major innovations do not always come from the brightest minds or the most expensive projects. Sometimes, they come from a technician who dares to ask a question that no one else has dared to formulate." MU4D Matrice Universelle à 4 Dimensions : L'axiome fondamental de la réalité ( Version Française )Nouveau modèle cosmologiqueGérald SALDUCCI - Introduction Le modèle cosmologique MU4D propose une vision novatrice de la structure fondamentale de l’espace-temps et de la dynamique de la matière qui en découle. Contrairement au modèle standard ΛCDM, souvent perçu comme centré sur la nature de l’univers à partir de notre point d’observation, une approche que l’on peut qualifier de « géocentrique », MU4D adopte une perspective conceptuelle « héliocentrique » visant à dépasser ce cadre établi, que je considère comme limitant la compréhension globale de l’univers. En fracturant ces limites conceptuelles, MU4D s’inscrit dans une approche plus universelle, fondée sur une matrice espace-temps définie comme un substrat quantique primordial, infini, isotrope et plat, sans bornes ni bords. Elle est par conséquent la source de l’énergie primordiale et de la matière, générées par les fluctuations de l’énergie du vide quantique, et éventuellement par des singularités plus hypothétiques telles que les fontaines blanches provocant des déformations locales de la métrique, donnant naissance à ce que l’on appelle des « univers bulles ». L’espace étant la manifestation du temps, cette approche conceptuelle offre une ontologie forte de l’espace-temps comme étant absolu. - Contexte Le modèle cosmologique standard ΛCDM repose sur une singularité initiale (Big Bang) et une topologie définie de l’univers, incorporant conceptuellement le tissu espace-temps et la matière dans une seule et même singularité pré Big Bang contrairement à mon modèle qui propose une alternative, considérant un espace-temps omnipotent sans début ni fin. Cette matrice est plate, isotrope, infinie et sans bord donc sans topologie globale.MU4D vise à unifier la physique quantique, la relativité restreinte et la relativité générale à partir de ce découplage conceptuel entre espace-temps et matière, cette dernière étant issue soit par effet Casimir résultant des fluctuations du vide quantique, soit par la présence éventuelle d’une singularité issue d’une fontaine blanche (trou blanc). - Description du modèle a) La matrice espace-temps : - La MU4D est un tissu fondamental ou un maillage dense de quanta d’espace-temps.- Elle est isotrope et plate dans toutes les directions, assurant une homogénéité et une absence de courbure globale.- Elle est infinie et sans bord, ce qui signifie qu’elle ne possède ni limites ni frontières spatiales.- Dans cette Matrice, l’espace est la manifestation du temps. b) Génération d’énergie et de matière : - L’énergie primordiale est produite par la création de « paires + et - » via l’effet Casimir lié aux fluctuations quantiques du vide. Particules qui en s’accumulant forment une poche dans la matrice dans laquelle cette énergie primordiale extrêmement concentrée forme un plasma qui à partir d’un seuil critique peut avoir la dynamique d’une fontaine blanche expulsant cette matière primordiale formant ainsi un « univers-bulle » post Big Bang libérant sa propre énergie cinétique.- Cette énergie primordiale se transforme par dissipation thermique en matière.- Il est également possible que des phénomènes tels que des fontaines blanches (trous blancs) génèrent localement des déformations de la matrice, formant ainsi des « univers bulles ». c) Univers-bulles et déformations locales : - Ces « univers-bulles » sont envisagés comme des déformations locales de la métrique dans la Matrice, caractérisées par une métrique distincte.- Ils pourraient être reliés par des ponts Einstein-Rosen (trous de ver), formant un réseau complexe comparable à un réseau neuronal. - Dualité temporelle Le modèle propose une dualité temporelle : - Un temps absolu global associé à la matrice, stable et uniforme.- Un temps relatif local dans les « univers bulles », résultant des déformations de la métrique.Cette dualité permet de concilier un temps fondamental universel avec des temps locaux variables, intégrant des aspects de la relativité et de la mécanique quantique. Ontologie conceptuelle MU4D ne se contente pas d’une description phénoménologique ou d’une simple modélisation mathématique, mais propose une nature fondamentale et structurante de la réalité cosmique. Cette ontologie forte repose sur plusieurs piliers : Substrat quantique primordial :L’espace-temps est envisagé comme une Matrice Universelle à 4 Dimensions, un substrat quantique fondamental, infini, isotrope et plat, sans bornes ni bords. Cette matrice est la réalité première, la trame sur laquelle tout se construit. Dissociation entre espace-temps et matière :Contrairement au modèle ΛCDM où espace-temps et matière sont intimement liés dès l’origine (Big Bang), MU4D dissocie ces deux entités. La matière émerge des fluctuations quantiques de cette matrice, notamment via l’effet Casimir, ou par des singularités hypothétiques comme les fontaines blanches. « Univers bulles » comme déformations locales :Les univers bulles sont des manifestations locales de déformations métriques dans cette matrice, chacune pouvant posséder ses propres propriétés physiques et temporelles, formant un réseau complexe. Perspective héliocentrique conceptuelle :En opposition à une vision centrée sur notre point d’observation (géocentrique), MU4D propose une vision plus universelle et globale, cherchant à dépasser les limites conceptuelles du modèle standard. - Implications et perspectives Offre une nouvelle perspective sur la nature de l’espace-temps et la création de matière. Propose une unification possible des théories physiques majeures. Ouvre la voie à des prédictions testables via l’étude des « univers bulles » et des ponts d’Einstein-Rosen. Conclusion : Ce nouveau modèle est une proposition ambitieuse visant à repenser la structure fondamentale de l’univers. En combinant un substrat quantique primordial infini avec des déformations locales potentielles, il offre un cadre unificateur et innovant pour la cosmologie moderne. "Les grandes innovations ne viennent pas toujours des esprits les plus brillants ou des projets les plus coûteux. Parfois, elles viennent d'un technicien qui ose poser une question que personne n'a osé formuler."

@techreport{salducci20264dimensional,
    author = "SALDUCCI, GERALD",
    title = "4-Dimensional Universal Matrix : The fundamental axiom of reality - New Cosmological Model",
    year = "2026",
    publisher = "Zenodo",
    abstract = {MU4D VIDEO - G.SALDUCCI NOUVEAU LOGO EN PDF ( Logiciel Blender ) / NEW LOGO IN PDF ( Blender Software ) 4DUM 4-Dimensional Universal Matrix : The Fundamental axiom of reality (English version)New Cosmological ModelGérald SALDUCCI - Introduction The 4DUM cosmological model proposes an innovative vision of the fundamental structure of space-time and the resulting dynamics of matter. Unlike the standard ΛCDM model, often perceived as centered on the nature of the universe from our observational point of view, an approach that can be called "geocentric," 4DUM adopts a conceptual "heliocentric" perspective aiming to transcend this established framework, which I consider limiting the global understanding of the universe. By breaking these conceptual limits, 4DUM fits into a more universal approach based on a space-time matrix defined as a primordial quantum substrate, infinite, isotropic, and flat, without boundaries or edges. It is consequently the source of primordial energy and matter, generated by fluctuations of quantum vacuum energy, and possibly by more hypothetical singularities such as white fountains causing local metric deformations, giving rise to so-called "bubble universes." Space being the manifestation of time, this conceptual approach offers a strong ontology of space-time as absolute. - Context Standard cosmological model ΛCDM rely on an initial singularity (Big Bang) and a defined topology of the universe, conceptually incorporating the fabric of space-time and matter into a single singularity before the Big Bang, contrary to my model which proposes an alternative, considering an omnipotent space-time without beginning or end. This matrix is flat, isotropic, infinite, and borderless, thus without global topology.4DUM aims to unify quantum physics, special relativity, and general relativity based on this conceptual decoupling between space-time and matter, the latter emerging either through the Casimir effect resulting from quantum vacuum fluctuations or through the possible presence of a singularity from a white fountain (white hole). - Model Description a) The space-time matrix: The 4DUM is a fundamental fabric or a dense mesh of space-time quanta.It is isotropic and flat in all directions, ensuring homogeneity and the absence of overall curvature.It is infinite and boundaryless, meaning it has neither spatial limits nor borders.In this Matrix, space is the manifestation of time. b) Generation of energy and matter: Primordial energy is produced by the creation of "+ and - pairs" via the Casimir effect linked to quantum vacuum fluctuations. These particles, accumulating, form a pocket in the matrix where this extremely concentrated primordial energy creates a plasma which, beyond a critical threshold, can exhibit the dynamics of a white fountain expelling this primordial matter, thus forming a "bubble universe" post-Big Bang, releasing its own kinetic energy.This primordial energy transforms into matter through thermal dissipation.It is also possible that phenomena such as white fountains (white holes) locally generate deformations of the matrix, thus forming "bubble universes." c) Bubble universes and local deformations: These "bubble universes" are envisioned as local deformations of the metric within the Matrix, characterized by a distinct metric.They could be connected by Einstein-Rosen bridges (wormholes), forming a complex network comparable to a neural network. - Temporal Duality The model proposes a temporal duality : - A global absolute time associated with the matrix, stable and uniform.- A local relative time in the "bubble universes," resulting from metric deformations.This duality reconciles a universal fundamental time with variable local times, integrating aspects of relativity and quantum mechanics. - Conceptual Ontology 4DUM does not limit itself to a phenomenological description or simple mathematical modeling but proposes a fundamental and structuring nature of cosmic reality. This strong ontology rests on several pillars: Primordial Quantum Substrate :Space-time is conceived as a 4-Dimensional Universal Matrix, a fundamental quantum substrate, infinite, isotropic, and flat, without boundaries or edges. This matrix is the primary reality, the framework upon which everything is constructed. Dissociation between Space-Time and Matter :Contrary to the ΛCDM model where space-time and matter are intimately linked from the origin (Big Bang), 4DUM dissociates these two entities. Matter emerges from quantum fluctuations of this matrix, notably via the Casimir effect, or from hypothetical singularities such as white fountains. Bubble Universes as Local Deformations :Bubble universes are local manifestations of metric deformations in this matrix, each potentially possessing its own physical and temporal properties, forming a complex network. Conceptual Heliocentric Perspective :Opposed to a view centered on our observation point (geocentric), 4DUM proposes a more universal and global vision, seeking to transcend the conceptual limits of the standard model. - Implications and Perspectives Offers a new perspective on the nature of space-time and matter creation. Proposes a possible unification of major physical theories. Opens the way to testable predictions via the study of bubble universes and Einstein-Rosen bridges. Conclusion : This new model is an ambitious proposal aiming to rethink the fundamental structure of the universe. By combining an infinite primordial quantum substrate with potential local deformations, it offers a unifying and innovative framework for modern cosmology. "Major innovations do not always come from the brightest minds or the most expensive projects. Sometimes, they come from a technician who dares to ask a question that no one else has dared to formulate." MU4D Matrice Universelle à 4 Dimensions : L'axiome fondamental de la réalité ( Version Française )Nouveau modèle cosmologiqueGérald SALDUCCI - Introduction Le modèle cosmologique MU4D propose une vision novatrice de la structure fondamentale de l’espace-temps et de la dynamique de la matière qui en découle. Contrairement au modèle standard ΛCDM, souvent perçu comme centré sur la nature de l’univers à partir de notre point d’observation, une approche que l’on peut qualifier de « géocentrique », MU4D adopte une perspective conceptuelle « héliocentrique » visant à dépasser ce cadre établi, que je considère comme limitant la compréhension globale de l’univers. En fracturant ces limites conceptuelles, MU4D s’inscrit dans une approche plus universelle, fondée sur une matrice espace-temps définie comme un substrat quantique primordial, infini, isotrope et plat, sans bornes ni bords. Elle est par conséquent la source de l’énergie primordiale et de la matière, générées par les fluctuations de l’énergie du vide quantique, et éventuellement par des singularités plus hypothétiques telles que les fontaines blanches provocant des déformations locales de la métrique, donnant naissance à ce que l’on appelle des « univers bulles ». L’espace étant la manifestation du temps, cette approche conceptuelle offre une ontologie forte de l’espace-temps comme étant absolu. - Contexte Le modèle cosmologique standard ΛCDM repose sur une singularité initiale (Big Bang) et une topologie définie de l’univers, incorporant conceptuellement le tissu espace-temps et la matière dans une seule et même singularité pré Big Bang contrairement à mon modèle qui propose une alternative, considérant un espace-temps omnipotent sans début ni fin. Cette matrice est plate, isotrope, infinie et sans bord donc sans topologie globale.MU4D vise à unifier la physique quantique, la relativité restreinte et la relativité générale à partir de ce découplage conceptuel entre espace-temps et matière, cette dernière étant issue soit par effet Casimir résultant des fluctuations du vide quantique, soit par la présence éventuelle d’une singularité issue d’une fontaine blanche (trou blanc). - Description du modèle a) La matrice espace-temps : - La MU4D est un tissu fondamental ou un maillage dense de quanta d’espace-temps.- Elle est isotrope et plate dans toutes les directions, assurant une homogénéité et une absence de courbure globale.- Elle est infinie et sans bord, ce qui signifie qu’elle ne possède ni limites ni frontières spatiales.- Dans cette Matrice, l’espace est la manifestation du temps. b) Génération d’énergie et de matière : - L’énergie primordiale est produite par la création de « paires + et - » via l’effet Casimir lié aux fluctuations quantiques du vide. Particules qui en s’accumulant forment une poche dans la matrice dans laquelle cette énergie primordiale extrêmement concentrée forme un plasma qui à partir d’un seuil critique peut avoir la dynamique d’une fontaine blanche expulsant cette matière primordiale formant ainsi un « univers-bulle » post Big Bang libérant sa propre énergie cinétique.- Cette énergie primordiale se transforme par dissipation thermique en matière.- Il est également possible que des phénomènes tels que des fontaines blanches (trous blancs) génèrent localement des déformations de la matrice, formant ainsi des « univers bulles ». c) Univers-bulles et déformations locales : - Ces « univers-bulles » sont envisagés comme des déformations locales de la métrique dans la Matrice, caractérisées par une métrique distincte.- Ils pourraient être reliés par des ponts Einstein-Rosen (trous de ver), formant un réseau complexe comparable à un réseau neuronal. - Dualité temporelle Le modèle propose une dualité temporelle : - Un temps absolu global associé à la matrice, stable et uniforme.- Un temps relatif local dans les « univers bulles », résultant des déformations de la métrique.Cette dualité permet de concilier un temps fondamental universel avec des temps locaux variables, intégrant des aspects de la relativité et de la mécanique quantique. Ontologie conceptuelle MU4D ne se contente pas d’une description phénoménologique ou d’une simple modélisation mathématique, mais propose une nature fondamentale et structurante de la réalité cosmique. Cette ontologie forte repose sur plusieurs piliers : Substrat quantique primordial :L’espace-temps est envisagé comme une Matrice Universelle à 4 Dimensions, un substrat quantique fondamental, infini, isotrope et plat, sans bornes ni bords. Cette matrice est la réalité première, la trame sur laquelle tout se construit. Dissociation entre espace-temps et matière :Contrairement au modèle ΛCDM où espace-temps et matière sont intimement liés dès l’origine (Big Bang), MU4D dissocie ces deux entités. La matière émerge des fluctuations quantiques de cette matrice, notamment via l’effet Casimir, ou par des singularités hypothétiques comme les fontaines blanches. « Univers bulles » comme déformations locales :Les univers bulles sont des manifestations locales de déformations métriques dans cette matrice, chacune pouvant posséder ses propres propriétés physiques et temporelles, formant un réseau complexe. Perspective héliocentrique conceptuelle :En opposition à une vision centrée sur notre point d’observation (géocentrique), MU4D propose une vision plus universelle et globale, cherchant à dépasser les limites conceptuelles du modèle standard. - Implications et perspectives Offre une nouvelle perspective sur la nature de l’espace-temps et la création de matière. Propose une unification possible des théories physiques majeures. Ouvre la voie à des prédictions testables via l’étude des « univers bulles » et des ponts d’Einstein-Rosen. Conclusion : Ce nouveau modèle est une proposition ambitieuse visant à repenser la structure fondamentale de l’univers. En combinant un substrat quantique primordial infini avec des déformations locales potentielles, il offre un cadre unificateur et innovant pour la cosmologie moderne. "Les grandes innovations ne viennent pas toujours des esprits les plus brillants ou des projets les plus coûteux. Parfois, elles viennent d'un technicien qui ose poser une question que personne n'a osé formuler."},
    url = "https://zenodo.org/doi/10.5281/zenodo.18208316",
    doi = "10.5281/zenodo.18208316",
    openalex = "W7120929521"
}