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Understanding the evolution of entropy in the universe is a fundamental aspect of cosmology. This paper investigates the evolution of entropy in a spatially flat $K=0$ universe, focusing on the contributions of matter, radiation, and dark…

General Relativity and Quantum Cosmology · Physics 2025-07-16 Tanisha Joshi , S. D Pathak

We examine a spatially flat Friedmann-Robertson-Walker (FRW) universe filled with interacting dark matter and a modified holographic Ricci dark energy (MHRDE). The interaction term is selected as a significant rational function of the total…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-05 Luis P. Chimento , Martín G. Richarte

The \Lambda CDM standard model, although an excellent parametrization of the present cosmological data, requires two as yet unobserved components, Dark Matter and Dark Energy, for more than 95% of the Universe. Faced to this unsatisfactory…

Cosmology and Nongalactic Astrophysics · Physics 2012-03-01 Aurélien Benoit-Lévy , Gabriel Chardin

The universe media is considered as a non-perfect fluid with bulk viscosity and described by a more general equation of state. We assume the bulk viscosity is a linear combination of the two terms: one is constant, and the other is…

Astrophysics · Physics 2009-03-19 Xin-He Meng , Jie Ren , Ming-Guang Hu

From a fractal perspective, the entropy bound of gravitational systems undergoes changes. Furthermore, in the cosmological setting, the conservation law of a perfect fluid is also altered in such systems, affecting spatial elements like…

General Relativity and Quantum Cosmology · Physics 2024-04-11 R. Jalalzadeh , S. Jalalzadeh , A. Sayahian Jahromi , H. Moradpour

(Abridged) Fundamental tensions between observations and dark-matter based cosmological models have emerged. This updated review has two purposes: to explore new tensions that have arisen in recent years, compounding the unresolved tensions…

Cosmology and Nongalactic Astrophysics · Physics 2023-09-27 Pavel Kroupa , Eda Gjergo , Elena Asencio , Moritz Haslbauer , Jan Pflamm-Altenburg , Nils Wittenburg , Nick Samaras , Ingo Thies , Wolfgang Oehm

We study the reduced phase space quantization of a closed Friedmann Universe, where matter content is constituted by two (no-interacting) fluids, namely dust (or cold dark matter) and radiation. It is shown that, for this particular model,…

General Relativity and Quantum Cosmology · Physics 2014-07-28 S. Jalalzadeh , P. V. Moniz

The R_h=ct Universe is a Friedmann-Robertson-Walker (FRW) cosmology which, like LCDM, assumes the presence of dark energy in addition to (baryonic and non-luminous) matter and radiation. Unlike LCDM, however, it is also constrained by the…

Cosmology and Nongalactic Astrophysics · Physics 2018-09-25 Fulvio Melia

The physics of light-matter interactions is strongly constrained by both the small value of the fine-structure constant and the small size of the atom. Overcoming these limitations is a long-standing challenge. Recent theoretical and…

Requiring all massless elementary fields to have conformal scaling symmetry removes a conflict between gravitational theory and the quantum theory of elementary particles and fields. Extending this postulate to the scalar field of the Higgs…

General Physics · Physics 2011-05-12 Robert K. Nesbet

We provide a simple mathematical description of the exchange of energy between two fluids in an expanding Friedmann universe with zero spatial curvature. The evolution can be reduced to a single non-linear differential equation which we…

General Relativity and Quantum Cosmology · Physics 2008-11-26 John D. Barrow , T. Clifton

In the first part of this note, we observe that a non-Riemannian piece in the affine connection (a "dark connection") leads to an algebraically determined, conserved, symmetric 2-tensor in the Einstein field equations that is a natural dark…

Cosmology and Nongalactic Astrophysics · Physics 2018-09-24 Ranit Das , Chethan Krishnan

We apply the gravity-thermodynamics conjecture, namely the first law of thermodynamics on the Universe horizon, but using the generalized Kaniadakis entropy instead of the standard Bekenstein-Hawking one. The former is a one-parameter…

General Relativity and Quantum Cosmology · Physics 2021-12-07 Andreas Lymperis , Spyros Basilakos , Emmanuel N. Saridakis

We present a full quantum mechanical three dimensional theory describing an electromagnetic field interacting with an ensemble of identical atoms. The theory is constructed such that it describes recent experiments on light-matter quantum…

Quantum Physics · Physics 2009-11-13 Martin W. Sørensen , Anders S. Sørensen

In this work we consider a recent proposal in which gravitational interactions are mediated via classical information and apply it to a relativistic context. We study a toy model of a quantized Friedman-Robertson-Walker (FRW) universe with…

General Relativity and Quantum Cosmology · Physics 2017-05-31 Natacha Altamirano , Paulina Corona-Ugalde , Kiran Khosla , Robert B. Mann , Gerard Milburn

I investigate through simulations the redshift dependence of several lensing measures for two cosmological models, a flat universe with a cosmological constant (\LambdaCDM), and an open universe (OCDM). I argue that quintessence models can…

Astrophysics · Physics 2007-05-23 Antonio C. C. Guimarães

The purpose of this article is twofold. First, by means of Padmanabhan's proposal on the emergence nature of gravity, we recover the $\Lambda$CDM model and the effect of the dark matter in the context of cosmology. Toward this goal, we use…

General Relativity and Quantum Cosmology · Physics 2025-05-06 Kimet Jusufi , Ahmad Sheykhi

The present work is an example of the application of the dynamical system analysis in the context of cosmology. Here cosmic evolution is considered in the background of homogeneous and isotropic flat Friedmann-Lema\^{i}tre-Robertson-Walker…

General Relativity and Quantum Cosmology · Physics 2020-11-20 Soumya Chakraborty , Sudip Mishra , Subenoy Chakraborty

Three models of a flat universe of coupled matter and dark energies with different low-redshift parameterizations of the dark energy equation of state are considered. The dark energy is assumed to vary with time like the trace of the…

Astrophysics · Physics 2011-08-04 A. -M. M. Abdel-Rahman , Ihab F. Riad

Cosmic structures determine how light propagates through the Universe and consequently must be taken into account in the interpretation of observations. In the standard cosmological model at the largest scales, such structures are either…

Cosmology and Nongalactic Astrophysics · Physics 2014-11-03 Samae Bagheri , Dominik J. Schwarz
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