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A novel fractal structure for the cosmological horizon, inspired by COVID-19 geometry, which results in a modified area entropy, is applied to cosmology in order to serve dark energy. The constraints based on a complete set of observational…

Cosmology and Nongalactic Astrophysics · Physics 2020-09-18 Mariusz P. Dabrowski , Vincenzo Salzano

Recently Verlinde has suggested a new approach to gravity which interprets gravitational interaction as a kind of entropic force. The new approach uses the holographic principle by stating that the information is kept on the holographic…

High Energy Physics - Theory · Physics 2010-12-09 R. A. Konoplya

We give an exact solution for the static force between two black holes at the turning points in their binary motion. The results are derived by Gibbs' principle and the Bekenstein-Hawking entropy applied to the apparent horizon surfaces in…

High Energy Physics - Theory · Physics 2015-05-28 Maurice H. P. M. van Putten

In an introductory manner, the nature of dark energy is addressed, how it is observed and what further tests are needed to reconstruct its properties. Several theoretical approaches to dark energy will be discussed.

Astrophysics · Physics 2007-05-23 Paul H. Frampton

Some essential conceptual aspects that will fill some logical gaps of the frame to interpret the gravity as an entropic force was investigated, we focus on some crucial issues that didn't emphasized in Verlinde's original…

General Relativity and Quantum Cosmology · Physics 2014-02-21 Qiao-Jun Cao

Dark energy might directly interact with cold dark matter. However, in such a scenario, an early-time large-scale instability occurs occasionally, which may be due to the incorrect treatment for the pressure perturbation of dark energy as a…

Cosmology and Nongalactic Astrophysics · Physics 2014-09-24 Yun-He Li , Jing-Fei Zhang , Xin Zhang

In an introductory manner, the nature of dark energy is addressed, how it is observed and what further tests are needed to reconstruct its properties. Several theoretical approaches to dark energy will be discussed. Finally, the dark…

Astrophysics · Physics 2007-05-23 Paul H. Frampton

Recent work has called into question whether nature can extract the rotational energy of a black hole via electromagnetic fields by appealing to an alleged ability to absorb current. We describe the strategies needed to properly treat the…

High Energy Astrophysical Phenomena · Physics 2021-11-16 David Garofalo , Chandra B. Singh

Since the discovery of the accelerated expansion of the universe, it was necessary to introduce a new component of matter distribution called dark energy. The standard cosmological model considers isotropy of the pressure and assumes an…

General Relativity and Quantum Cosmology · Physics 2012-10-25 R. Chan , M. F. A. da Silva , J. F. Villas da Rocha

Using the Wald's relation between the Noether charge of diffeomorphisms and the entropy for a generic spacetime possessing a bifurcation surface, we introduce a method to obtain a family of higher order derivatives effective actions from…

General Relativity and Quantum Cosmology · Physics 2015-05-18 Francesco Caravelli , Leonardo Modesto

We discuss the possibility that the existence of dark energy may be due to the presence of a spin zero field $\phi(x)$, either elementary or composite. In the presence of other matter field, the transformation $\phi(x)\to \phi(x) +$…

Astrophysics · Physics 2009-11-10 T. D. Lee

We present a unifying treatment of dark energy and modified gravity that allows distinct conformal-disformal couplings of matter species to the gravitational sector. In this very general approach, we derive the conditions to avoid ghost and…

Cosmology and Nongalactic Astrophysics · Physics 2015-09-16 Jérôme Gleyzes , David Langlois , Michele Mancarella , Filippo Vernizzi

An extension to the Einstein-Cartan (EC) action is discussed in terms of cosmological solutions. The torsion incorporated in the EC Lagrangian is assumed to be totally anti-symmetric, represented by a time-like axial vector $S^\mu$. The…

Cosmology and Nongalactic Astrophysics · Physics 2022-03-30 David Benisty , Eduardo I. Guendelman , Armin van de Venn , David Vasak , Jürgen Struckmeier , Horst Stoecker

In this paper we present a possible origin of dark matter and dark energy from a solution of the Einstein's equation to a primordial universe, which was presented in a previous paper. We also analyze the Dirac's equation in this primordial…

General Relativity and Quantum Cosmology · Physics 2010-10-01 A. C. V. V. de Siqueira

This review summarizes recent attempts to reconstruct the expansion history of the Universe and to probe the nature of dark energy. Reconstruction methods can be broadly classified into parametric and non-parametric approaches. It is…

Astrophysics · Physics 2008-11-26 Varun Sahni , Alexei Starobinsky

I briefly review our current understanding of dark matter and dark energy. The first part of this paper focusses on issues pertaining to dark matter including observational evidence for its existence, current constraints and the `abundance…

Astrophysics · Physics 2022-07-19 Varun Sahni

In this paper is proposed a geometric solution to the dark energy, assuming that the space can be divided into regions of size $\sim L_{p}$ and energy $\sim E_{p}$. Significantly this assumption generate a energy density similar to the…

General Relativity and Quantum Cosmology · Physics 2011-02-08 Miguel Angel García-Aspeitia

The observed dark energy in the universe might give particles inertial mass. We investigate one realization of this idea, that the dark energy field might be a decayed scalar component of a supermultiplet field in the early universe that…

Astrophysics · Physics 2007-05-23 Robert J. Nemiroff , Bijunath Patla

Inspired by Verlinde's idea, some modified versions of entropic gravity have appeared in the literature. Extending them in a unified formalism, we derive the generalized gravitational equations accordingly. From gravitational equations, the…

High Energy Physics - Theory · Physics 2012-11-27 Tower Wang

Using Tsallis statistics and its relation with Boltzmann entropy, the Tsallis entropy content of black holes is achieved, a result in full agreement with a recent study (Phys. Lett. B 794, 24 (2019)). In addition, employing Kaniadakis…

General Relativity and Quantum Cosmology · Physics 2020-08-18 H. Moradpour , A. H. Ziaie , M. Kord Zangeneh
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