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.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this paper, the authors investigated the age-graphic dark energy models which were recently proposed to explain the dark energy-dominated universe and calculated their equation of states and squared speeds of sound.
180 citations
TL;DR: In this paper, it was shown that the low quadrupole amplitude is associated with spatial curvature, and that the quadrupoles amplitude can be reproduced if the primordial spectrum truncates on scales comparable to the curvature scale.
Abstract: The temperature anisotropy power spectrum measured with the Wilkinson Microwave Anisotropy Probe (WMAP) at high multipoles is in spectacular agreement with an inflationary Lambda-dominated cold dark matter cosmology. However, the low order multipoles (especially the quadrupole) have lower amplitudes than expected from this cosmology, indicating a need for new physics. Here we speculate that the low quadrupole amplitude is associated with spatial curvature. We show that positively curved models are consistent with the WMAP data and that the quadrupole amplitude can be reproduced if the primordial spectrum truncates on scales comparable to the curvature scale.
180 citations
180 citations
TL;DR: In this article, a universe is envisioned in which there was a major creation episode when the mean universal density was about 10 to the -27 g/cu cm. Explicit equations are given for the creation of matter; in a cosmological approximation, these equations lead to expressions for the time-dependence of the cosmology scale factor S(t), but do not entail, as big bang cosmology does, that S( t) tend to zero at some finite time t.
Abstract: A universe is envisioned in which there was a major creation episode when the mean universal density was about 10 to the -27 g/cu cm. Explicit equations are given for the creation of matter; in a cosmological approximation, these equations lead to expressions for the time-dependence of the cosmological scale factor S(t), but do not entail, as big bang cosmology does, that S(t) tend to zero at some finite time t. The equations therefore possess a universality that is absent from big bang cosmology. Creation occurs when certain conservation equations involving the gradient of a scalar field C(i) are satisfied.
180 citations
TL;DR: In this article, the authors consider a brane universe with standard-model fields localized on a 3-brane in 6 spacetime dimensions, and show that if the spacetime is rotationally symmetric about the brane, local quantities in the bulk are insensitive to the couplings on the 3brane.
Abstract: We consider `brane universe' scenarios with standard-model fields localized on a 3-brane in 6 spacetime dimensions. We show that if the spacetime is rotationally symmetric about the brane, local quantities in the bulk are insensitive to the couplings on the brane. This potentially allows compactifications where the effective 4-dimensional cosmological constant is independent of the couplings on the 3-brane. We consider several possible singularity-free compactification mechanisms, and find that they do not maintain this property. We also find solutions with naked spacetime singularities, and we speculate that new short-distance physics can become important near the singularities and allow a compactification with the desired properties. The picture that emerges is that standard-model loop contributions to the effective 4-dimensional cosmological constant can be cut off at distances shorter than the compactification scale. At shorter distance scales, renormalization effects due to standard-model fields renormalize the 3-brane tension, which changes a deficit angle in the transverse space without affecting local quantities in the bulk. For a compactification scale of order 10−2 mm, this gives a standard-model contribution to the cosmological constant in the range favored by cosmology.
180 citations