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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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31 May 2022
TL;DR: In this paper , a relativistic model of the universe is proposed, in which the geometry describes a 4D version of the 2-sheeted hyperboloid that is isotropic, homogeneous in space at a given time and inhomogeneous in time.
Abstract: This paper proposes a relativistic model of the Universe in which the geometry describes a 4D version of the 2-sheeted hyperboloid that is isotropic, homogeneous in space at a given time and inhomogeneous in time. The radius of this metric is temporal as opposed to spatial. It predicts both a Universe and Anti-Universe moving in opposite directions of time undergoing an expansion phase, followed by a collapsing phase. Using only the current age of the Universe and transition redshift, it predicts the accelerated expansion and it is shown that its Hubble diagram fits currently available supernova and quasar data as well as predicting a Hubble constant H0 ≈ 71.6km/s/M pc. The angular term of the metric describes time dilation caused by the relativistic kinematic precession effect known as Thomas Precession which can be interpreted as spin about the time dimension. The model also makes two novel predictions: that the early Universe should have structures older than expected due to an increased amount of proper time relative to coordinate time in that era and that the background Universe should appear brighter than current models predict
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TL;DR: In this article, the distance-redshift relation in a universe filled with point particles was studied, and it was shown that the statistical nature of the amplification is independent of the number of particles.
Abstract: We study the distance-redshift relation in a universe filled with point particles, and discuss what the universe looks like when we make the number of particles N very large, while fixing the averaged mass density. Using the Raychaudhuri equation and a simple analysis of the probability of strong lensing effects, we show that the statistical nature of the amplification is independent of N, and clarify the appearance of the point particle universe.
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TL;DR: In this article, the effects of primordial non-Gaussianities in the primordial universe on the baryonic structure formation process were investigated by relating the cosmic star formation rate in Gaussian and nonGaussian scenarios to the detectability of high-redshift sources of reionization.
Abstract: We investigate the effects of primordial non-Gaussianities in the primordial Universe on the baryonic structure formation process. By relating the cosmic star formation rate in Gaussian and non-Gaussian scenarios to the detectability of high-redshift sources of reionization, we derive the expected Gamma-Ray Burst rate in the different models. We find that counts of high-redshift Gamma-Ray Bursts can be used as cosmological probes of non-Gaussianities and that they are suitable candidates to distinguish non-Gaussian effects at early epochs.
15 Oct 2001
TL;DR: In this paper, the authors use the CMB to study the properties of the early universe and of the universe at large scales, using the Hot Big Bang model to find out what happened before and the background geometry of our universe.
Abstract: The CMB is the fundamental tool to study the properties of the early universe and of the
universe at large scales. In the framework of the Hot Big Bang model, when we look to
the CMB we look back in time to the end of the plasma era, at a redshift ~ 1000, when
the universe was ~ 50000 times younger, ~ 1000 times hotter and ~ 10^9 times denser
than today. The image of the CMB can be used to study the physical processes there, to
infer what happened before, and also to study the background geometry of our Universe.
TL;DR: The cosmological event horizon entropy and the apparent horizon entropy of the ΛCDM and the Bianchi type I universe model with viscosity has been calculated numerically and analytically in the large time limit as mentioned in this paper.
Abstract: The cosmological event horizon entropy and the apparent horizon entropy of the ΛCDM and the Bianchi type I Universe model with viscosity has been calculated numerically, and analytically in the large time limit. It is shown that for these Universe models the cosmological event horizon entropy increases with time and for large times it approaches a finite maximum value. The effect of viscosity upon the entropy is also studied and we have found that its role is to decrease the entropy. The bigger the viscosity coefficient is the less the entropy will be. Furthermore, the radiation entropy for the ΛCDM Universe model with and without viscosity is investigated, and together with the cosmological event horizon entropy are used to examine the validity of the generalized second law of thermodynamics, which states that the total rate of change of entropy of the Universe is never negative, in this Universe model.