Topic
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: Based on the formulation of the reconstruction for the k-essence model, which was recently proposed in arXiv:1001.0220 [hep-th], the authors explicitly construct cosmological model to unify the late-time acceleration and the inflation in the early universe.
Abstract: Based on the formulation of the reconstruction for the k-essence model, which was recently proposed in arXiv:1001.0220 [hep-th], we explicitly construct cosmological model to unifying the late-time acceleration and the inflation in the early universe.
3 citations
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TL;DR: In this article, the authors address the issue related to the particle horizon problem in the bouncing universe models and present a toy example of a bouncing universe where they specify the conditions which dictate the presence of a particle horizon.
Abstract: As our understanding of the past in a bouncing universe is limited, it becomes difficult to propose a cosmological model which can give some understanding of the causal structure of the bouncing universe. In this article we address the issue related to the particle horizon problem in the bouncing universe models. It is shown that in many models the particle horizon does not exist, and consequently the horizon problem is trivially solved. In some cases a bouncing universe can have a particle horizon and we specify the conditions for its existence. In the absence of a particle horizon the Hubble surface specifies the causal structure of a bouncing universe. We specify the complex relationship between the Hubble surface and the particle horizon when the particle horizon exists. The article also address the issue related to the event horizon in a bouncing universe. A toy example of a bouncing universe is first presented where we specify the conditions which dictate the presence of a particle horizon. Next we specify the causal structures of three widely used bouncing models. The first case is related to quintom matter bounce model, the second one is loop quantum cosmology based bounce model and lastly f(R) gravity induced bounce model. We present a brief discussion on the horizon problem in bouncing cosmologies. We point out that the causal structure of the various bounce models fit our general theoretical predictions.
3 citations
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TL;DR: In this paper, a refined version of a recently introduced method for analysing the dynamics of an inhomogeneous irrotational dust universe is presented, and a fully nonperturbative numerical computation of the time dependence of volume in this framework leads to the following results.
Abstract: A refined version of a recently introduced method for analysing the dynamics of an inhomogeneous irrotational dust universe is presented. A fully non-perturbative numerical computation of the time dependence of volume in this framework leads to the following results. If the initial state of the universe is Einstein-de Sitter with small Gaussian perturbations, then there is no acceleration even though the inhomogeneities strongly affect the evolution. A universe with a positive background curvature can exhibit acceleration, but not in conjunction with reasonable values for the Hubble rate. Thus the correct values for both quantities can be achieved only by introducing a positive cosmological constant. Possible loopholes to this conclusion are discussed; in particular, acceleration as an illusion created by peculiarities of light propagation in an inhomogeneous universe is still possible. Independently of the cosmological constant question, the present formalism should provide an important tool for precision cosmology.
3 citations
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01 Oct 2006
TL;DR: In this article, the authors derived the Brans-Dicke relation with respect to the cosmological constant of the universe from the conjecture that the total energy of the entire universe is null.
Abstract: By analogy with the original Brans-Dicke relation GM2R � 1 , several other similar relations can be obtained, relating the angular momentum, absolute temperature T , and the cosmological ”constant”, with R , where R , M stand for the radius (scale-factor) and the mass of the causally related Universe. We show here that these properties, which characterize Machian Universes, can be derived from the conjecture that the total energy of the Universe is null, and imply that the angular momentum runs like R 2 ; T , like R − 1 2 ; so that the total entropy of the Universe increases with R 3 2 , and, then, also as M 3 2 . This also solves the ”loss of information paradox”,
3 citations
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30 Jul 2012
TL;DR: In this article, the cosmological precision data can be used to set very strict constraints on axions and axion-like particles (ALPs) produced thermally in the big bang.
Abstract: Cosmological precision data can be used to set very strict constraints on axions and axion-like particles (ALPs) produced thermally in the big bang. We briefly review the known bounds and propose two new constraints for axions and ALPs decaying in the early universe, based upon the concomitant dilution of baryon and neutrino densities, using WMAP7 and other cosmological data.
3 citations