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 paper, the tension between the Planck observations of the cosmic microwave background anisotropies and the local measurement of the Hubble constant was investigated, and it was shown that the ΛCDM+Neff model is most favored by the current observations, and this model can reduce the tension to 1.87σ level.
Abstract: We wish to investigate whether there is an extension to the base ΛCDM cosmology that can resolve the tension between the Planck observation of the cosmic microwave background anisotropies and the local measurement of the Hubble constant. We consider various plausible extended models in this work, and we use the Planck 2015 observations, combined with the baryon acoustic oscillation data, the JLA type Ia supernovae data, and the local measurement of the Hubble constant (by Riess et al. in 2016), to make an analysis. We find that the holographic dark energy plus sterile neutrino model can reduce the tension to be at the 1.11σ level, but this model is obviously not favored by the current observations. Among these extended models, the ΛCDM+Neff model is most favored by the current observations, and this model can reduce the tension to be at the 1.87σ level. By a careful test, we conclude that none of these extended models can convincingly resolve the H0 tension.
140 citations
TL;DR: In this paper, the existence of a mirror universe of fermions and forces is shown to be impossible, and the possible existence of such a universe is thereby excluded, as shown in Figure 1.
140 citations
Carnegie Learning1, Carnegie Institution for Science2, University of Chile3, University of Victoria4, Texas A&M University5, Centre national de la recherche scientifique6, Collège de France7, University of Cape Town8, University of Toronto9, Fermilab10, University of Chicago11, University of Notre Dame12, Las Cumbres Observatory Global Telescope Network13, University of California, Santa Barbara14, Institute of Cosmology and Gravitation, University of Portsmouth15, Johns Hopkins University16, Space Telescope Science Institute17, University of Pennsylvania18, Pennsylvania State University19, University of Oxford20, University of Pittsburgh21
TL;DR: The Carnegie Supernova Project (CSP) is designed to measure the luminosity distance for Type Ia supernovae (SNe Ia) as a function of redshift, and to set observational constraints on the dark energy contribution to the total energy content of the universe as mentioned in this paper.
Abstract: The Carnegie Supernova Project (CSP) is designed to measure the luminosity distance for Type Ia supernovae (SNe Ia) as a function of redshift, and to set observational constraints on the dark energy contribution to the total energy content of the universe The CSP differs from other projects to date in its goal of providing an I-band rest-frame Hubble diagram Here, we present the first results from near-infrared observations obtained using the Magellan Baade telescope for SNe Ia with 01
140 citations
TL;DR: In this article, the potential of the ghost condensate field is chosen such that the cosmological bounce is stable against the presence of anisotropic stress, and this model allows for the realization of the ''matter bounce'' scenario, an alternative to inflationary cosmology for the generation of the observed primordial fluctuations in which the inhomogeneities originate as quantum vacuum perturbations which exit the Hubble radius in the matterdominated phase of contraction.
Abstract: Assuming the existence of a scalar field which undergoes ``ghost condensation and which has a suitably chosen potential, it is possible to obtain a non-singular bouncing cosmology in the presence of regular matter and radiation. The potential for the ghost condensate field can be chosen such that the cosmological bounce is stable against the presence of anisotropic stress. Cosmological fluctuations on long wavelengths relevant to current cosmological observations pass through the bounce unaffected by the new physics which yields the bounce. Thus, this model allows for the realization of the ``matter bounce scenario, an alternative to inflationary cosmology for the generation of the observed primordial fluctuations in which the inhomogeneities originate as quantum vacuum perturbations which exit the Hubble radius in the matter-dominated phase of contraction.
140 citations
TL;DR: In this article, the authors study models of late-time cosmic acceleration in terms of scalar-tensor theories generalized to include a certain class of nonlinear derivative interaction of the scalar field, and show that the expansion history until today is almost indistinguishable from that of the $\ensuremath{\Lambda}mathrm{CDM}$ model or some (phantom) dark energy models, but the fate of the universe depends clearly on the model parameter.
Abstract: We study models of late-time cosmic acceleration in terms of scalar-tensor theories generalized to include a certain class of nonlinear derivative interaction of the scalar field. The nonlinear effect suppresses the scalar-mediated force at short distances to pass solar-system tests of gravity. It is found that the expansion history until today is almost indistinguishable from that of the $\ensuremath{\Lambda}\mathrm{CDM}$ model or some (phantom) dark energy models, but the fate of the universe depends clearly on the model parameter. The growth index of matter density perturbations is computed to show that its past asymptotic value is given by $9/16$, while the value today is as small as 0.4.
140 citations