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.

Status of neutrino properties and future prospects - Cosmological and astrophysical constraints

Abstract: Cosmological observations are a powerful probe of neutrino properties, and in particular of their mass. In this review, we first discuss the role of neutrinos in shaping the cosmological evolution at both the background and perturbation level, and describe their effects on cosmological observables such as the cosmic microwave background and the distribution of matter at large scale. We then present the state of the art concerning the constraints on neutrino masses from those observables, and also review the prospects for future experiments. We also briefly discuss the prospects for determining the neutrino hierarchy from cosmology, the complementarity with laboratory experiments, and the constraints on neutrino properties beyond their mass.

Phenomenology of D-brane inflation with general speed of sound

Abstract: A characteristic of D-brane inflation is that fluctuations in the inflaton field can propagate at a speed significantly less than the speed of light. This yields observable effects that are distinct from those of single-field slow-roll inflation, such as a modification of the inflationary consistency relation and a potentially large level of non-Gaussianities. We present a numerical algorithm that extends the inflationary flow formalism to models with general speed of sound. For an ensemble of D-brane-inflation models parametrized by the Hubble parameter and the speed of sound as polynomial functions of the inflaton field, we give qualitative predictions for the key inflationary observables. We discuss various consistency relations for D-brane inflation, and compare the qualitative shapes of the warp factors we derive from the numerical models with analytical warp factors considered in the literature. Finally, we derive and apply a generalized microphysical bound on the inflaton field variation during brane inflation. While a large number of models are consistent with current cosmological constraints, almost all of these models violate the compactification constraint on the field range in four-dimensional Planck units. If the field range bound is to hold, then models with a detectable level of non-Gaussianity predict a blue scalar spectral index, and a tensor component that is far below the detection limit of any future experiment.

Entropy from Extra Dimensions

Abstract: The phenomenon of ''dynamical compactification'' in a universe with 4+n/sub c/ dimensions is studied, and it is found that if the whole process is adiabatic, entropy is pumped into the effective four-dimensional universe. Some cosmological consequences of this fact are discussed.

Improved Cosmological Constraints from Gravitational Lens Statistics

Abstract: We combine the Cosmic Lens All-Sky Survey (CLASS) with new Sloan Digital Sky Survey (SDSS) data on the local velocity dispersion distribution function of E/S0 galaxies, � (� ), to derive lens statistics constraints on � � and � m. Previous studies of this kind relied on a combination of the E/S0 galaxy luminosity function and the FaberJackson relation to characterize the lens galaxy population. However, ignoring dispersion in the Faber-Jackson relation leads to a biased estimate of � (� ) and therefore biased and overconfident constraints on the cosmological parameters. The measured velocity dispersion function from a large sample of E/S0 galaxies provides a more reliable method for probing cosmology with strong lens statistics. Our new constraints are in good agreement with recent results from the redshift-magnitude relation of Type Ia supernovae. Adopting the traditional assumption that the E/S0 velocity function is constant in comoving units, we find a maximum likelihood estimate of � � ¼ 0:74 0:78 for a spatially flat universe (where the range reflects uncertainty in the number of E/S0 lenses in the CLASS sample) and a 95% confidence upper bound of � � < 0:86. If � (� ) instead evolves in accord with the extended PressSchechter theory, then the maximum likelihood estimate for � � becomes 0.72‐0.78, with the 95% confidence upper bound � � < 0:89. Even without assuming flatness, lensing provides independent confirmation of the evidence from Type Ia supernovae for a nonzero dark energy component in the universe. Subject headingg cosmological parameters — cosmology: observations — cosmology: theory — gravitational lensing

Precision cosmology from future lensed gravitational wave and electromagnetic signals

Abstract: The standard siren approach of gravitational wave cosmology appeals to the direct luminosity distance estimation through the waveform signals from inspiralling double compact binaries, especially those with electromagnetic counterparts providing redshifts. It is limited by the calibration uncertainties in strain amplitude and relies on the fine details of the waveform. The Einstein telescope is expected to produce 104–105 gravitational wave detections per year, 50–100 of which will be lensed. Here, we report a waveform-independent strategy to achieve precise cosmography by combining the accurately measured time delays from strongly lensed gravitational wave signals with the images and redshifts observed in the electromagnetic domain. We demonstrate that just 10 such systems can provide a Hubble constant uncertainty of 0.68% for a flat lambda cold dark matter universe in the era of third-generation ground-based detectors. Gravitational wave sources can be used as cosmological probes through a direct distance luminosity relation. Here, the authors demonstrate that the time delay between lensed gravitational wave signals and their electromagnetic counterparts can reduce the uncertainty in the Hubble constant.