scispace - formally typeset
Search or ask a question
Topic

Particle horizon

About: Particle horizon is a research topic. Over the lifetime, 2096 publications have been published within this topic receiving 69137 citations.


Papers
More filters
Journal ArticleDOI
TL;DR: In this article, the authors revisited the holographic principle from a cosmological viewpoint and showed that the holography principle requires the existence of a graceful exit mechanism, which renders the universe non-singular by connecting pre-and post-big-bang phases smoothly.
Abstract: String cosmology is revisited from a cosmological viewpoint of the holographic principle put forward by 't Hooft, and by Fischler and Susskind. It is shown that the holography principle requires the existence of a `graceful exit' mechanism, which renders the universe non-singular by connecting pre- and post-big-bang phases smoothly. It is proven that a flat universe is consistent with the holography principle only if it starts with an absolutely cold and vacuous state and particle entropy is produced during the `graceful exit' period. An open universe can always satisfy the holography principle no matter what the initial state of the universe is.

61 citations

Journal ArticleDOI
TL;DR: In this paper, the authors explore the viability of a bulk viscous matter-dominated universe to explain the present accelerated expansion of the universe and find that from all the possible scenarios for the Universe, the preferred one by the best estimated values of (\zeta, \zeta_1) is that of an expanding universe beginning with a Big- Bang, followed by a decelerated expansion at early times, and with a smooth transition in recent times to an accelerated expansion epoch that is going to continue forever.
Abstract: We explore the viability of a bulk viscous matter-dominated Universe to explain the present accelerated expansion of the Universe. The model is composed by a pressureless fluid with bulk viscosity of the form \zeta = \zeta_0 + \zeta_1 * H where \zeta_0 and \zeta_1 are constants and H is the Hubble parameter. The pressureless fluid characterizes both the baryon and dark matter components. We study the behavior of the Universe according to this model analyzing the scale factor as well as some curvature scalars and the matter density. On the other hand, we compute the best estimated values of \zeta_0 and \zeta_1 using the type Ia Supernovae (SNe Ia) probe. We find that from all the possible scenarios for the Universe, the preferred one by the best estimated values of (\zeta_0, \zeta_1) is that of an expanding Universe beginning with a Big- Bang, followed by a decelerated expansion at early times, and with a smooth transition in recent times to an accelerated expansion epoch that is going to continue forever. The predicted age of the Universe is a little smaller than the mean value of the observational constraint coming from the oldest globular clusters but it is still inside of the confidence interval of this constraint. A drawback of the model is the violation of the local second law of thermodynamics in redshifts z >= 1. However, when we assume \zeta_1 = 0, the simple model \zeta = \zeta_0 evaluated at the best estimated value for \zeta_0 satisfies the local second law of thermodynamics, the age of the Universe is in perfect agreement with the constraint of globular clusters, and it also has a Big-Bang, followed by a decelerated expansion with the smooth transition to an accelerated expansion epoch in late times, that is going to continue forever.

61 citations

Journal ArticleDOI
23 May 2021-Symmetry
TL;DR: In this paper, the equivalence between the entropic DE and the generalized holographic dark energy (HDE) was established for the quintessence and for the Ricci DE model.
Abstract: In the formalism of generalized holographic dark energy (HDE), the holographic cut-off is generalized to depend upon LIR=LIRLp,L˙p,L¨p,⋯,Lf,L˙f,⋯,a with Lp and Lf being the particle horizon and the future horizon, respectively (moreover, a is the scale factor of the Universe). Based on such formalism, in the present paper, we show that a wide class of dark energy (DE) models can be regarded as different candidates for the generalized HDE family, with respective cut-offs. This can be thought as a symmetry between the generalized HDE and different DE models. In this regard, we considered several entropic dark energy models—such as the Tsallis entropic DE, the Renyi entropic DE, and the Sharma–Mittal entropic DE—and found that they are indeed equivalent with the generalized HDE. Such equivalence between the entropic DE and the generalized HDE is extended to the scenario where the respective exponents of the entropy functions are allowed to vary with the expansion of the Universe. Besides the entropic DE models, the correspondence with the generalized HDE was also established for the quintessence and for the Ricci DE model. In all the above cases, the effective equation of state (EoS) parameter corresponding to the holographic energy density was determined, by which the equivalence of various DE models with the respective generalized HDE models was further confirmed. The equivalent holographic cut-offs were determined by two ways: (1) in terms of the particle horizon and its derivatives, (2) in terms of the future horizon horizon and its derivatives.

61 citations

Journal ArticleDOI
TL;DR: In this paper, the authors study the possibility to probe the spatial geometry of the universe by supernova measurement and illustrate with an accelerating universe model with infinite-volume extra dimensions, for which the 1σ level supernova results indicate that the universe is closed.

61 citations

Journal ArticleDOI
TL;DR: In this paper, the authors consider the expansion of the universe powered by the gravitationally induced "adiabatic" matter creation and demonstrate how matter creation works well with the expanding universe.
Abstract: In a flat Friedmann–Lemaitre–Robertson–Walker (FLRW) geometry, we consider the expansion of the universe powered by the gravitationally induced ‘adiabatic’ matter creation. To demonstrate how matter creation works well with the expanding universe, we have considered a general creation rate and analysed this rate in the framework of dynamical analysis. The dynamical analysis hints the presence of a non-singular universe (without the big bang singularity) with two successive accelerated phases, one at the very early phase of the universe (i.e. inflation), and the other one describes the current accelerating universe, where this early, late accelerated phases are associated with an unstable fixed point (i.e. repeller) and a stable fixed point (attractor), respectively. We have described this phenomena by analytic solutions of the Hubble function and the scale factor of the FLRW universe. Using Jacobi last multiplier method, we have found a Lagrangian for this matter creation rate describing this scenario of the universe. To match with our early physics results, we introduce an equivalent dynamics driven by a single scalar field, discuss the associated observable parameters and compare them with the latest Planck data sets. Finally, introducing the teleparallel modified gravity, we have established an equivalent gravitational theory in the framework of matter creation.

60 citations


Network Information
Related Topics (5)
Black hole
40.9K papers, 1.5M citations
88% related
Dark matter
41.5K papers, 1.5M citations
86% related
Gauge theory
38.7K papers, 1.2M citations
85% related
Neutrino
45.9K papers, 1M citations
84% related
Supersymmetry
29.7K papers, 1.1M citations
83% related
Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202320
202247
20216
202010
201910
201814