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Particle horizon
About: Particle horizon is a research topic. Over the lifetime, 2096 publications have been published within this topic receiving 69137 citations.
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TL;DR: In this paper, the authors considered an anti-de-sitter universe filled by quantum conformal matter with the contribution from the usual tachyon and a perfect fluid, and the radius corresponding to this universe was calculated and the effect of the Tachyon potential was discussed, in particular concerning the possibility to get an accelerated scale factor for the proposed model.
Abstract: We consider an Anti-de Sitter universe filled by quantum conformal matter with the contribution from the usual tachyon and a perfect fluid. The model represents the combination of a trace-anomaly annihilated and a tachyon driven Anti-de Sitter universe. The influence exerted by the quantum effects and by the tachyon on the AdS space is studied. The radius corresponding to this universe is calculated and the effect of the tachyon potential is discussed, in particular, concerning the possibility to get an accelerated scale factor for the proposed model (which yields an accelerated expansion of the AdS type of universe). Fulfillment of the cosmological energy conditions in the model is also investigated.
10 citations
TL;DR: In this paper, the authors consider the fate of the observable universe in the light of the discovery of a dark energy component to the cosmic energy budget and examine the constraints on phenomena that may prevent the eternal acceleration of our patch of the universe.
Abstract: We consider the fate of the observable universe in the light of the discovery of a dark energy component to the cosmic energy budget. We extend results for a cosmological constant to a general dark energy component and examine the constraints on phenomena that may prevent the eternal acceleration of our patch of the universe. We find that the period of accelerated cosmic expansion has not lasted long enough for observations to confirm that we are undergoing inflation; such an observation will be possible when the dark energy density has risen to between 90% and 95% of the critical. The best we can do is make cosmological observations in order to verify the continued presence of dark energy to some high redshift. Having done that, the only possibility that could spoil the conclusion that we are inflating would be the existence of a disturbance (the surface of a true vacuum bubble, for example) that is moving toward us with sufficiently high velocity, but is too far away to be currently observable. Such a disturbance would have to move toward us with speed greater than about $0.8c$ in order to spoil the late-time inflation of our patch of the universe and yet avoid being detectable.
10 citations
TL;DR: In this paper, the authors considered a higher dimensional gravity theory with a negative kinetic energy scalar field and a cosmological constant, and they found that the theory admits an exact cosmology solution for the scale factor of our universe.
Abstract: We consider a higher dimensional gravity theory with a negative kinetic energy scalar field and a cosmological constant. We find that the theory admits an exact cosmological solution for the scale factor of our universe. It has the feature that the universe undergoes a continuous transition from deceleration to acceleration at some finite time. This transition time can be interpreted as that of recent acceleration of our universe.
10 citations
TL;DR: In this article, the authors review the physics of the Grishchuk-Zel'dovich effect which describes the impact of large amplitude, superhorizon gravitational field fluctuations on the cosmic microwave background anisotropy power spectrum.
Abstract: We review the physics of the Grishchuk-Zel'dovich effect which describes the impact of large amplitude, superhorizon gravitational field fluctuations on the cosmic microwave background anisotropy power spectrum. Using the latest determination of the spectrum by the Wilkinson Microwave Anisotropy Probe satellite, we infer a lower limit on the present length scale of such fluctuations of $3.9\ifmmode\times\else\texttimes\fi{}{10}^{3}$ times the cosmological particle horizon (at the 95% confidence level).
10 citations
TL;DR: In this article, the authors study the thermodynamics of the Cardassian universe and regard it as the origin of this cosmological model, and find that the corresponding entropy obeys ordinary area law when the area of the trapping horizon is small, while it becomes a constant when area is going to be large in the original and modified polytropic Cardassian model.
Abstract: In the Cadassian universe, one can explain the acceleration of the universe without introducing dark energy component. However, the dynamical equations of this model can not be directly obtained from the action principle. Recently, works on the relation between thermodynamics and gravity indicates that gravity force may not be the fundamental force. In this paper, we study the thermodynamics of the Cardassian universe, and regard it as the origin of this cosmological model. We find that the corresponding entropy obeys ordinary area law when the area of the trapping horizon is small, while it becomes a constant when area is going to be large in the original and modified polytropic Cardassian model, and it has a maximum value in the exponential one. It seems that the Cardassian universe only contains finite information according to the holographic principle, which states that all the information in the bulk should be encoded in the boundary of the bulk.
10 citations