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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01 Jan 2006
TL;DR: In this paper, an expression for the gravitational constant was derived based on a Planck scale underpinning for the universe, which exhibits it as a distributional effect over all the particles of the universe.
Abstract: Based on a Planck scale underpinning for the universe, we deduce an expression for the gravitational constant which exhibits it as a distributional effect over all the particles of the universe. This solves a long standing puzzle, the so called Weinberg formula which gives a microphysical parameter in terms of a cosmic parameter. This was also discussed on the basis of a cosmology that correctly predicted a dark energy driven accelerating universe - the linkage is now established.
07 Mar 2022
TL;DR: In this article , the authors studied the Bianchi type I model with modifications of scale factors in different directions in the generalized Bianchi Type I metric equation, and compared the results with the ΛCDM model and also with available cosmological observational data.
Abstract: Abstract According to standard cosmology, the universe is homogeneous and isotropic at large scales. However, some anisotropies can be observed at the local scale in the universe through various ways. Here we have studied the Bianchi type I model with customizing the scale factors to understand the anisotropic nature of the universe. We have considered two cases with slight modifications of scale factors in different directions in the generalized Bianchi Type I metric equation, and compared the results with the ΛCDM model and also with available cosmological observational data. Through this study, we also want to predict the possible degree of anisotropy present in the early universe and its evolution to current time by calculating the value of density parameter for anisotropy (Ω σ ) for both low and high redshift (z) along with the possible relative anisotropy that exist among different directions. It is found that there was a significant amount of anisotropy in the early universe and the anisotropic nature of the universe vanishes at the near past and the present epochs. Thus at near past and present stages of the universe there is no effective distinction between this anisotropic model and the standard ΛCDM model.
TL;DR: In this paper, it was shown that the non-oscillatory solution coincides with the adiabatic solution up to 6.6 order for all the evolution of the universe with cosmological interest.
Abstract: As the red shift shows no sign of oscillatory behavior in an expanding universe we postulate that the energyω
k
of a scalar field does not oscillate in such a universe. In the massive case, expanding the differential equation forω
k
in mass powers, we find that the nonoscillatory solution coincides with the adiabatic solution up to them
6 order. We also demonstrate that this solution is unique for all the evolution of the universe with cosmological interest. Using the nonoscillatory solution as the one that defines the good vacuum state, we compute the particle and energy creation for a simple model of expanding universe. Both quantities turn out to be finite.
01 Jan 2001
TL;DR: The evolution of the flat Einstein-deSitter model universe into a cosmological isothermal sphere has been studied in this article, where the symmetry and metric of an isothermal model differ from those of its Robertson-Walker progenitor.
Abstract: The expansion of the flat Einstein-deSitter model universe constantly slows, and ultimately ceases. This facilitates the eventual condensation of galaxies into a small number of great clusters. Consequently the model may evolve asymptotically into a cosmological isothermal sphere. The symmetries and metric of an isothermal model differ from those of its Robertson-Walker progenitor, suggesting that the evolution leads to a phase transition in the infinite future.
TL;DR: In this article, the authors study a possible fate of universe, one in which there is neither a rip singularity, which results in the disintegration of bound systems, nor an endless expansion; instead the universe will be quasi-static.
Abstract: We study a possible fate of universe, one in which there is neither a rip singularity, which results in the disintegration of bound systems, nor an endless expansion; instead the universe will be quasi-static. We discuss the parameterization of the corresponding evolution and the reconstruction of the scalar field model. We find, with the parameterization consistent with the current observation, that the current universe might arrive at a quasi-static phase after less than 20 Gyr.