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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, a model of the universe filled with various kinds of matter characterized by different equations of state is explored at phenomenological level, and it is shown that introducing each kind of matter is equivalent to a certain choice of a gauge condition, the gauge condition describing a medium with a given equation of state.
Abstract: We explore at phenomenological level a model of the Universe filled with various kinds of matter characterized by different equations of state. We show that introducing of each kind of matter is equivalent to a certain choice of a gauge condition, the gauge condition describing a medium with a given equation of state. The case of a particular interest is when one kind of matter (de Sitter false vacuum) dominates at the early stage of the Universe evolution while another kind (radiation, or ultrarelativistic gas) dominates at its later stage. We can, therefore, consider different asymptotic regimes for the early and later stages of the Universe existence. These regimes are described by solutions to the Wheeler - DeWitt equation for the Universe with matter in that given state, and, at the same time, in the "extended phase space" approach to quantum geometrodynamics the regimes are described by solutions to a Schrodinger equation associated with a choice of some gauge condition. It is supposed that, from the viewpoint of the observer located at the later stage of the Universe evolution, solutions for a Lambda-dominated early Universe would decay.
TL;DR: In this paper, the effect of the ratio of matter to radiation in the universe was investigated and the matter-radiation model of the universe is studied and the effect on the ratio is investigated.
Abstract: The matter-radiation model of the universe is studied and the effect of the ratio of matter to radiation investigated.
Posted Content•
TL;DR: In this paper, the back-reaction effect of the vacuum energy of quantized massless matter fields at finite temperatures is investigated, and it is shown that the original spatial singularity is avoided and that the universe is maintained all times at a critical density.
Abstract: The Friedmann paradigm for a dynamical universe emanating from a spacetime singularity is critically reviwed. Quantum effects, playing the essential role at the very early stages, suggests that the universe may follow different course to that presented by the standard Friedmann solutions. The investigation of the back-reaction effect of the vacuum energy of quantized massless matter fields at finite temperatures shows that the original spatial singularity is avoided and that the universe is maintained all times at a critical density. Instead of having a universe that was created at once we have an emergent universe with energy being created continuously so as to maintain the overall density at its critical value. The calculations presented here provide a basis to construct a dynamical model for the universe where all the known problems of the standard big bang can be avioded from start without the need to assume the occurence of an inflation phase.
Posted Content•
01 Jan 2015
TL;DR: In this article, a detailed analysis of the cosmic dipoles in f(R,T) cosmological model is presented, showing that the maximum anisotropic deviation direction is (l,b) = (137.7 −32).
Abstract: Recent astronomical observations show that the universe may be anisotropic on large scales. The Union2 SnIa data hint that the universe has a preferred direction. If such a cosmological privileged axis indeed exists, one has to consider an anisotropic expanding Universe, instead of the isotropic cosmological model. In this paper, we present a detailed analysis of the cosmic dipoles in f(R,T) Cosmological Model. the maximum anisotropic deviation direction is (l,b) = (137.7 −32
10 Jul 2006
TL;DR: In this article, the authors review recent advances in cosmic topology since it has entered a new era of experimental tests, including the recent analysis of CMB data provided by the WMAP satellite, which suggests a finite universe with the topology of the Poincare dodecahedral spherical space.
Abstract: In this talk I review recent advances in cosmic topology since it has entered a new era of experimental tests. High redshift surveys of astronomical sources and accurate maps of the Cosmic Microwave Background radiation (CMB) are beginning to hint at the shape of the universe, or at least to limit the wide range of possibilities. Among those possibilites are surprising “wrap around” universe models in which space, whatever its curvature, may be smaller than the observable universe and generate topological lensing effects on a detectable cosmic scale. In particular, the recent analysis of CMB data provided by the WMAP satellite suggest a finite universe with the topology of the Poincare dodecahedral spherical space. Such a model of a “small universe”, the volume of which would represent only about 80% the volume of the observable universe, offers an observational signature in the form of a predictable topological lens effect on one hand, and rises new issues on the early universe physics on the other hand.