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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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01 Jan 2008
TL;DR: In this article, the authors investigated how large the magnitude of a negative cosmological constant is allowed to be and pointed out that a measure of the evolution of the dark energy equation of state may be a good discriminator.
Abstract: The presently accelerating universe may keep accelerating forever, eventually run into the event horizon problem, and thus be in conflict with the superstring idea. In the other way around, the current accelerating phase as well as the fate of the universe may be swayed by a negative cosmological constant, which dictates a big crunch. Based on the current observational data, in this paper we investigate how large the magnitude of a negative cosmological constant is allowed to be. In addition, for distinguishing the sign of the cosmological constant via observations, we point out that a measure of the evolution of the dark energy equation of state may be a good discriminator. Hopefully future observations will provide much more detailed information about dark energy and thereby indicates the sign of the cosmological constant as well as the fate of the presently accelerating universe.
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TL;DR: In this paper, the size of the classical electron, which is a stable elemental particle with the smallest concentration of matter in Nature, was used to explain the very big size of Earth.
Abstract: In this paper, it is proposed that the size of the classical electron, which is a stable elemental particle with the smallest concentration of matter in Nature, can be used to explain the very big size of the Universe In order to reach that objective, the apparent size of heavenly bodies as seemed each other at very big distances in space, is used as a fundamental concept Also, it is proved that the size, shape, mass, and future of the Universe are ruled by the speed of light, and the range of gravitational interactions
29 May 2009
TL;DR: In this paper, the theoretical basis of our understanding of the large scale structure of the universe is presented, together with a description of the issues raised by the search of primordial non-Gaussianities.
Abstract: These lectures present the theoretical basis of our understanding of the large scale structure of the universe. The different types of primordial metric fluctuations are described as well as their evolution from super‐Hubble to sub‐Hubble scales in the local universe. It is shown how the only adiabatic mode can explain what we have so far observed of the large‐scale structure of the Universe.These notes also present our current understanding of the origin of these metric perturbation in the inflationary context. Various models of inflation are presented together with their motivations. These notes are completed with a description of the issues raised by the search of primordial non‐Gaussianities. Those issues are presented both in the context of classical perturbation theory and in the physics of the early universe.
TL;DR: In this article, a fluid homogeneous cosmologioal model with a Robertson-Walker metric and positive curvature is proposed, which affords an interpretation to the matter production process in the following terms.
Abstract: A fluid homogeneous cosmologioal model is proposed with a Robertson-Walker metric and positive curvature. The Einstein field equations are modified through the following two assumptions: the principle of Mach in Whitrow’s formulation and a new version of Hoyle’s vector field. The present model affords an interpretation to the matter production process in the following terms: the matter injection into the observable universe is due to the work done along cosmic expansion by a negative-pressure substratum and to the variation of a negative field energy. The properties of the expansion function and the vector field demand a negative cosmological constant.
TL;DR: In this article, Vilenkin's results are generalized by allowing for strings, domain walls, and various kinds of compressed matter that contribute to the potential through which the tunneling occurs, and the conditions of applicability of the quasi-classical approximation in the calculation of these quantities are found.
Abstract: Quantum tunneling of the universe from “nothing” into a de Sitter vacuum, interpreted as the birth of the universe from a vacuum, is considered Vilenkin's results are generalized by allowing for strings, domain walls, and various kinds of compressed matter that contribute to the potential through which the tunneling occurs The energy spectrum of the universe in the quantum pre-de Sitter stage, the coefficient of passage through the potential barrier, which describes the probability of birth of the universe, and the conditions of applicability of the quasi-classical approximation in the calculation of these quantities are found