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, a frame-independent formulation of the Boltzmann equation is presented, which allows simultaneous implementation of the good aspects of the two frames in a clear and straightforward way.
Abstract: Scalar-tensor theories of gravity can be formulated in different frames, most notably, the Einstein and the Jordan one. While some debate still persists in the literature on the physical status of the different frames, a frame transformation in scalar-tensor theories amounts to a local redefinition of the metric, and then should not affect physical results. We analyze the issue in a cosmological context. In particular, we define all the relevant observables (redshift, distances, cross sections, ...) in terms of frame-independent quantities. Then, we give a frame-independent formulation of the Boltzmann equation, and outline its use in relevant examples such as particle freeze-out and the evolution of the cosmic microwave background photon distribution function. Finally, we derive the gravitational equations for the frame-independent quantities at first order in perturbation theory. From a practical point of view, the present approach allows the simultaneous implementation of the good aspects of the two frames in a clear and straightforward way.
160 citations
TL;DR: In this article, the authors investigated the impact of the running vacuum model (RVM) and related models on the controversy of the precise value of H 0, which is the first ever parameter of modern cosmology and one of the prime parameters in the field, still goes on and on after over half a century of measurements.
160 citations
TL;DR: The Dark Ages Radio Explorer (DARE) as mentioned in this paper was proposed to measure the expected spectral features in the sky-averaged, redshifted 21-cm signal over a radio bandpass of 40-120 MHz.
160 citations
TL;DR: In this article, the spectral index of the Lyman-α forest 1D flux power spectrum is used to estimate the neutrino mass under weak lensing constraints on (Ωm,σ8) and has the same small tension with Planck.
Abstract: The Lyman-α forest 1D flux power spectrum is a powerful probe of several cosmological parameters. Assuming a ΛCDM cosmology including massive neutrinos, we find that the latest SDSS DR14 BOSS and eBOSS Lyman-α forest data is in very good agreement with current weak lensing constraints on (Ωm, σ8) and has the same small level of tension with Planck. We did not identify a systematic effect in the data analysis that could explain this small tension, but we show that it can be reduced in extended cosmological models where the spectral index is not the same on the very different times and scales probed by CMB and Lyman-α data. A particular case is that of a ΛCDM model including a running of the spectral index on top of massive neutrinos. With combined Lyman-α and Planck data, we find a slight (3σ) preference for negative running, αs= −0.010 ± 0.004 (68%CL). Neutrino mass bounds are found to be robust against different assumptions. In the ΛCDM model with running, we find ∑ mν 5.3 keV (95%CL).
160 citations
TL;DR: In this paper, the authors used the local curvature to investigate the possible existence of non-Gaussianity/asymmetry in the Wilkinson Microwave Anisotropy Probe data.
Abstract: We use the local curvature to investigate the possible existence of non-Gaussianity/asymmetry in the Wilkinson Microwave Anisotropy Probe data. Considering the full sky, we find results that are consistent with the Gaussian assumption. However, strong non-Gaussian features emerge when considering the northern and southern Galactic hemisphere separately, particularly on scales between 1° and 5°. Quite interestingly, the maximum non-Gaussianity is found for hemispheres centered near the ecliptic poles, which might suggest the presence of some systematic effect. The direction of the asymmetry seems consistent with the findings by Eriksen et al.
159 citations