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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 origin of seed perturbations in the universe is studied within the framework of a specific minisuperspace model and it is shown that the creation of the universe as a result of a quantum transition from a flat empty spacetime would lead to a flat FLRW (Friedmann-Lemaitre-Robertson-Walker) universe with weak inhomogeneous perturbation at large wavelengths.
Abstract: The origin of seed perturbations in the universe is studied within the framework of a specific minisuperspace model. It is shown that the creation of the universe as a result of a quantum transition from a flat empty spacetime would lead to a flat FLRW (Friedmann-Lemaitre-Robertson-Walker) universe with weak inhomogeneous perturbations at large wavelengths. The power spectrum of these perturbations is found to be scale invariant at horizon crossing (i.e., the Harrison-Zel'dovich spectrum)
4 citations
TL;DR: In this article, a class of homogeneous and isotropic zero-curvature Robertson-Walker models with bulk viscosity is studied and the time dependence of the cosmological constant in terms of varying γ index is established.
Abstract: A class of homogeneous and isotropic zero-curvature Robertson-Walker models with bulk viscosity is studied. Solutions are obtained with the parameter gamma of the “γ-law” equation of state p = (γ – 1)ρ in which the adiabatic parameter gamma varies continuously as the universe expands. A unified description of the early evolution of the universe is presented with constant bulk viscosity and time-dependent bulk viscosity in which an inflationary period is followed by a radiation-dominated phase. We also establish the time dependence of the cosmological constant in terms of varying γ index. Some physical properties of the models are also discussed.
4 citations
Posted Content•
01 Jan 2014
TL;DR: The scale principle or scale law is the first Meta law we, humans, have discovered as discussed by the authors, and it is known as the scale law of scale principle (SLP) in physics.
Abstract: In 2012 I formulated the scale principle or scale law which was published at viXra.org in June this year. This paper is about a cosmological analysis based on this new law. On previous papers I have shown that several fundamental laws such as the Heisenberg’s uncertainty principle, the black hole entropy, the Bohr postulate, the De Broglie wavelength-momentum relationship, the formula for the Schwarzschild radius, Einstein’s relativistic energy equation, Newton’s law of universal gravitation and Schrodinger’s equation obey this formulation. Furthermore the author’s previous research suggests that the mass of the Higgs boson, the radius of the proton, the radius of the electron might obey this law as well. The present paper shows that the scale law correctly describes several cosmological issues such as the age of the universe (this analysis includes the latest data from the Planck spacecraft- 2013), the universe mass density, the radius of the present particle horizon and finally the Friedmann’s equation. This simple law is the first Meta law we, humans, have discovered.
4 citations
TL;DR: In this article , it is shown that the cosmological abundances of the different components of the universe remain unchanged over time, even as the universe expands, and that such situations are not fine-tuned, but are actually global attractors within certain cosmology frameworks.
Abstract: One signature of an expanding universe is the time-variation of the cosmological abundances of its different components. For example, a radiation-dominated universe inevitably gives way to a matter-dominated universe, and critical moments such as matter-radiation equality are fleeting. In this paper, we point out that this lore is not always correct, and that it is possible to obtain a form of "stasis" in which the relative cosmological abundances $\Omega_i$ of the different components remain unchanged over extended cosmological epochs, even as the universe expands. Moreover, we demonstrate that such situations are not fine-tuned, but are actually global attractors within certain cosmological frameworks, with the universe naturally evolving towards such long-lasting periods of stasis for a wide variety of initial conditions. The existence of this kind of stasis therefore gives rise to a host of new theoretical possibilities across the entire cosmological timeline, ranging from potential implications for primordial density perturbations, dark-matter production, and structure formation all the way to early reheating, early matter-dominated eras, and even the age of the universe.
4 citations
TL;DR: In this paper, the influence of the cosmological constant and physical processes on the evolution of the primordial cloud collapse was investigated, and it was shown that the physical mechanisms (photon drag, photon cooling, recombination, etc.) amplify perturbations.
Abstract: We investigate the influence both of the cosmological constant and of the physical processes that take place during the evolution of the Universe on the primordial cloud collapse. We study the evolution of a cloud with a density perturbation, b, from the recombination era to the present. As an example, we study an initial perturbation bj = 10-6 for a cloud of mass 10\ 105 and 106 M0 • In particular, we study the influence of the physical processes on the evolution of the peculiar velocity factor, f=d In bid Ina, where 'a' is the scalefactor ofthe Universe. We compare our results with the analytic expression for f obtained by Lahav et al. Our results show that the physical mechanisms (photon drag, photon cooling, recombination, etc.) amplify perturbations, and the cosmological constant is particularly important in a Universe dominated by it with a small matter density.
4 citations