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Cosmology

About: Cosmology is a research topic. Over the lifetime, 18004 publications have been published within this topic receiving 631028 citations. The topic is also known as: physical cosmology & cosmologies.


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Journal ArticleDOI
TL;DR: In this paper, the authors provide a brief overview of models in both categories as well as their phenomenology and characteristic observable signatures in cosmology and introduce a rigorous distinction between dark energy and modified gravity based on the strong and weak equivalence principles.
Abstract: Understanding the reason for the observed accelerated expansion of the Universe represents one of the fundamental open questions in physics. In cosmology, a classification has emerged among physical models for this acceleration, distinguishing between dark energy and modified gravity. In this review, we provide a brief overview of models in both categories as well as their phenomenology and characteristic observable signatures in cosmology. We also introduce a rigorous distinction between dark energy and modified gravity based on the strong and weak equivalence principles.

277 citations

Journal ArticleDOI
TL;DR: In this article, the authors derived upper and lower bounds for the basic physical parameters (mass-radius ratio, anisotropy, redshift and total energy) for arbitrary anisotropic general relativistic matter distributions in the presence of a cosmological constant.
Abstract: We derive the upper and lower limits for the basic physical parameters (mass-radius ratio, anisotropy, redshift and total energy) for arbitrary anisotropic general relativistic matter distributions in the presence of a cosmological constant. The values of these quantities are strongly dependent on the value of the anisotropy parameter (the difference between the tangential and radial pressure) at the surface of the star. In the presence of the cosmological constant, a minimum mass configuration with a given anisotropy does exist. Anisotropic compact stellar-type objects can be much more compact than the isotropic ones, and their radii may be close to their corresponding Schwarzschild radii. Upper bounds for the anisotropy parameter are also obtained from the analysis of the curvature invariants. General restrictions for the redshift and the total energy (including the gravitational contribution) for anisotropic stars are obtained in terms of the anisotropy parameter. Values of the surface redshift parameter greater than two could be the main observational signature for anisotropic stellar-type objects. © 2006 IOP Publishing Ltd.

276 citations

Journal ArticleDOI
TL;DR: In this article, a limited set of only 37 cosmological models (the "Coyote Universe" suite) is used to predict the nonlinear matter power spectrum to 1% over a prior parameter range set by current cosmic microwave background observations.
Abstract: The power spectrum of density fluctuations is a foundational source of cosmological information. Precision cosmological probes targeted primarily at investigations of dark energy require accurate theoretical determinations of the power spectrum in the nonlinear regime. To exploit the observational power of future cosmological surveys, accuracy demands on the theory are at the 1% level or better. Numerical simulations are currently the only way to produce sufficiently error-controlled predictions for the power spectrum. The very high computational cost of (precision) N-body simulations is a major obstacle to obtaining predictions in the nonlinear regime, while scanning over cosmological parameters. Near-future observations, however, are likely to provide a meaningful constraint only on constant dark energy equation of state, "wCDM", cosmologies. In this paper, we demonstrate that a limited set of only 37 cosmological models—the "Coyote Universe" suite—can be used to predict the nonlinear matter power spectrum to 1% over a prior parameter range set by current cosmic microwave background observations. This paper is the second in a series of three, with the final aim to provide a high-accuracy prediction scheme for the nonlinear matter power spectrum for wCDM cosmologies.

276 citations

Journal ArticleDOI
Wayne Hu1
TL;DR: In this article, a phenomenological model for a generalized dark matter (GDM) component and its effect on large-scale structure and CMB anisotropies is introduced. But the model requires not only a model for its equation of state but also one for its full stress tensor.
Abstract: The next generation of cosmic microwave background (CMB) experiments, galaxy surveys, and high-redshift observations can potentially determine the nature of the dark matter observationally. With this in mind, we introduce a phenomenological model for a generalized dark matter (GDM) component and discuss its effect on large-scale structure and CMB anisotropies. Specifying the gravitational influence of the otherwise non-interacting GDM requires not merely a model for its equation of state but one for its full stress tensor. From consideration of symmetries, conservation laws, and gauge invariance, we construct a simple but powerful 3 component parameterization of these stresses that exposes the new phenomena produced by GDM. Limiting cases include: a particle component (e.g. WIMPS, radiation or massive neutrinos), a cosmological constant, and a scalar field component. Intermediate cases illustrate how the clustering properties of the dark matter can be specified independently of its equation of state. This freedom allows one to alter the amplitude and features in the matter power spectrum relative to those of the CMB anisotropies while leaving the background cosmology fixed. Conversely, observational constraints on such properties can help determine the nature of the dark matter.

276 citations

Journal ArticleDOI
TL;DR: In this article, the authors used the conditional luminosity function (CLF) and data from the 2dFGRS to constrain the average relation between light and mass in a LCDM cosmology with Omegam=0.23 and sigma_8 = 0.74.
Abstract: We use the conditional luminosity function (CLF) and data from the 2dFGRS to constrain the average relation between light and mass in a LCDM cosmology with Omega_m=0.23 and sigma_8=0.74 (hereafter WMAP3 cosmology). Reproducing the observed luminosity dependence of the galaxy two-point correlation function results in average mass-to-light ratios that are about 35 percent lower than in a LCDM cosmology with Omega_m=0.3 and sigma_8=0.9 (hereafter WMAP1 cosmology). This removes an important problem with previous halo occupation models which had a tendency to predict cluster mass-to-light ratios that were too high. For the WMAP3 cosmology our model yields average mass-to-light ratios, central galaxy luminosities, halo occupation numbers, satellite fractions, and luminosity-gap statistics, that are all in excellent agreement with those obtained from a 2dFGRS group catalogue and from other independent studies. We also use our CLF model to compute the probability distribution P(M|L_cen), that a central galaxy of luminosity L_cen resides in a halo of mass M. We find this distribution to be much broader than what is typically assumed in HOD models, which has important implications for the interpretation of galaxy-galaxy lensing data. Finally, reproducing the luminosity dependence of the pairwise velocity dispersions in the 2dFGRS requires relatively low mass-to-light ratios for clusters and a satellite fraction that decreases strongly with increasing luminosity. This is only marginally consistent with our CLF constraints. We argue that a cosmology with parameters between those of the WMAP1 and WMAP3 cosmologies is likely to yield results with a higher level of consistency.

275 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20241
2023768
20221,518
2021737
2020784
2019782