Topic
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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TL;DR: In this article, the authors developed a unified phantom cosmology where the same scalar plays the role of early time (phantom) inflaton and late-time dark energy, and the recent transition from decelerating to accelerating phase is described too by the scalar field.
376 citations
TL;DR: In this paper, the authors use the linear intrinsic alignment model as a base and compare it to an alternative model and data, and find that when intrinsic alignments are included two or more times as many bins are required to obtain 80% of the available information.
Abstract: Cosmic shear constrains cosmology by exploiting the apparent alignments of pairs of galaxies due to gravitational lensing by intervening mass clumps. However, galaxies may become (intrinsically) aligned with each other, and with nearby mass clumps, during their formation. This effect needs to be disentangled from the cosmic shear signal to place constraints on cosmology. We use the linear intrinsic alignment model as a base and compare it to an alternative model and data. If intrinsic alignments are ignored then the dark energy equation of state is biased by ~50%. We examine how the number of tomographic redshift bins affects uncertainties on cosmological parameters and find that when intrinsic alignments are included two or more times as many bins are required to obtain 80% of the available information. We investigate how the degradation in the dark energy figure of merit depends on the photometric redshift scatter. Previous studies have shown that lensing does not place stringent requirements on the photometric redshift uncertainty, so long as the uncertainty is well known. However, if intrinsic alignments are included the requirements become a factor of three tighter. These results are quite insensitive to the fraction of catastrophic outliers, assuming that this fraction is well known. We show the effect of uncertainties in photometric redshift bias and scatter. Finally, we quantify how priors on the intrinsic alignment model would improve dark energy constraints.
375 citations
TL;DR: In this article, the future evolution of the dark energy universe in modified gravities including $F(R)$ gravity, string-inspired scalar Gauss-Bonnet and modified GaussBonnet ones, and ideal fluid with the inhomogeneous equation of state (EoS) was investigated.
Abstract: We investigate the future evolution of the dark energy universe in modified gravities including $F(R)$ gravity, string-inspired scalar-Gauss-Bonnet and modified Gauss-Bonnet ones, and ideal fluid with the inhomogeneous equation of state (EoS). Modified Friedmann-Robertson-Walker (FRW) dynamics for all these theories may be presented in universal form by using the effective ideal fluid with an inhomogeneous EoS without specifying its explicit form. We construct several examples of the modified gravity which produces accelerating cosmologies ending at the finite-time future singularity of all four known types by applying the reconstruction program. Some scenarios to resolve the finite-time future singularity are presented. Among these scenarios, the most natural one is related with additional modification of the gravitational action in the early universe. In addition, late-time cosmology in the non-minimal Maxwell-Einstein theory is considered. We investigate the forms of the non-minimal gravitational coupling which generates the finite-time future singularities and the general conditions for this coupling in order that the finite-time future singularities cannot emerge. Furthermore, it is shown that the non-minimal gravitational coupling can remove the finite-time future singularities or make the singularity stronger (or weaker) in modified gravity.
374 citations
TL;DR: In this paper, the authors investigated f(T) cosmology in both the background, as well as in the perturbation level, and presented the general formalism for reconstructing the equivalent one-parameter family of f (T) models for any given dynamical dark energy scenario.
Abstract: We investigate f(T) cosmology in both the background, as well as in the perturbation level, and we present the general formalism for reconstructing the equivalent one-parameter family of f(T) models for any given dynamical dark energy scenario Despite the completely indistinguishable background behavior, the perturbations break this degeneracy and the growth histories of all these models differ from one another As an application we reconstruct the f(T) equivalent for quintessence, and we show that the deviation of the matter overdensity evolution is strong for small scales and weak for large scales, while it is negligible for large redshifts
374 citations
TL;DR: In this article, a list of 28 independent measurements of the Hubble parameter between redshifts 0.07 ≤ z ≤ 2.3 was compiled and used to place constraints on model parameters of constant and time-evolving dark energy cosmologies.
Abstract: We compile a list of 28 independent measurements of the Hubble parameter between redshifts 0.07 ≤ z ≤ 2.3 and use this to place constraints on model parameters of constant and time-evolving dark energy cosmologies. These H(z) measurements by themselves require a currently accelerating cosmological expansion at about, or better than, 3σ confidence. The mean and standard deviation of the six best-fit model deceleration-acceleration transition redshifts (for the three cosmological models and two Hubble constant priors we consider) are z da = 0.74 ± 0.05, in good agreement with the recent Busca et al. determination of z da = 0.82 ± 0.08 based on 11 H(z) measurements between redshifts 0.2 ≤ z ≤ 2.3, almost entirely from baryon-acoustic-oscillation-like data.
373 citations