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We investigate cosmological scenarios with spin-gravity coupling. In particular, due to the spin of the baryonic and dark matter particles and its coupling to gravity, they probe an effective spin-dependent metric, which can be calculated…

General Relativity and Quantum Cosmology · Physics 2023-05-23 Giovanni Otalora , Emmanuel N. Saridakis

In this paper, we explore the particle creation scenario in the context of $f(\mathcal{G})$ gravity in flat-FLRW metric. For this purpose, from the perspective of thermodynamics and considering an adiabatic universe, we obtain the modified…

General Relativity and Quantum Cosmology · Physics 2025-05-30 S. Ganjizadeh , Alireza Amani , M. A. Ramzanpour

We propose a cosmological model that makes a significant step toward solving the coincidence problem of the near similarity at the present of the dark energy and dark matter components. Our cosmology has the following properties: a) among…

Astrophysics · Physics 2008-11-26 Luca Amendola , Domenico Tocchini-Valentini

We revisit the question of frame equivalence in Quantum Field Theory in the presence of gravity, a situation of relevance for theories aiming to describe the early Universe dynamics and Inflation in particular. We show that in those cases,…

High Energy Physics - Theory · Physics 2019-09-04 Kevin Falls , Mario Herrero-Valea

Based upon the holographic principle, Jacobson demonstrated that the spacetime can be viewed as a gas of atoms with a related entropy given by the Bekenstein-Hawking formula. Following this argument, Friedmann equations can be derived by…

General Relativity and Quantum Cosmology · Physics 2015-10-13 C. A. S. Silva

A new approach for arbitrary dimension to the Friedmann cosmological models is presented. Taking suitable changes of the parameters of the spacetime the harmonic motion equations appear, where the curvature determines the angular frequency.…

General Relativity and Quantum Cosmology · Physics 2014-03-03 Rafael M. Rubio , Juan J. Salamanca

We study the formation of large-scale structure in universes dominated by dark matter and driven to accelerated expansion by f(R) gravity in the Palatini formalism. If the dark matter is cold, practically all of these models are ruled out…

Astrophysics · Physics 2008-11-26 Tomi Koivisto

We discuss flat Friedmann-Lemaitre-Robertson-Walker (FLRW) metric-affine cosmology where the metric and connection as well as the matter energy-momentum and hypermomentum all obey the symmetry of spatial homogeneity and isotropy. In…

General Relativity and Quantum Cosmology · Physics 2026-04-07 Ilaria Andrei , Damianos Iosifidis , Laur Järv , Margus Saal

We describe a new type of generalized gravity-matter models where $f(R)=R+R^2$ gravity couples in a non-conventional way to a scalar "inflaton" field, to a second scalar "darkon" field responsible for dark energy/dark matter unification, as…

General Relativity and Quantum Cosmology · Physics 2018-01-30 Eduardo Guendelman , Emil Nissimov , Svetlana Pacheva

Recently, a Hamilton-Jacobi method beyond semiclassical approximation in black hole physics was developed by \emph{Banerjee} and \emph{Majhi}\cite{beyond0}. In this paper, we generalize their analysis of black holes to the case of…

High Energy Physics - Theory · Physics 2014-11-18 Tao Zhu , Ji-Rong Ren

A Gauss-Bonnet dark energy model is considered, which is inspired in string/M-theory and takes also into account quantum contributions. Those are introduced from a conformal quantum anomaly. The corresponding solutions for the Hubble rate,…

General Relativity and Quantum Cosmology · Physics 2009-02-11 Emilio Elizalde , John Quiroga Hurtado , Hector Ivan Arcos

The previously proposed modification of the standard (flat) inflationary $\Lambda CDM$ model in which the inflaton field(s) and ``dark energy" are replaced by the vacum in expanding Friedmann-Lema\^itre-Robertson-Walker Universe is studied.…

General Relativity and Quantum Cosmology · Physics 2026-03-24 Robert Alicki

We suggest a Lorentz non-invariant generalization of the unimodular gravity theory, which is classically equivalent to general relativity with a locally inert (devoid of local degrees of freedom) perfect fluid having an equation of state…

General Relativity and Quantum Cosmology · Physics 2017-10-02 A. O. Barvinsky , A. Yu. Kamenshchik

A solution to Einstein's field equations via the Friedman equations is shown to produce a cosmological model that is in exact agreement with the measurements made by the dark energy astronomers. All the essential physical parameters are…

General Physics · Physics 2012-06-26 James G. Gilson

Considering Verlinde's entropic gravity proposal, we focus the effects of fermionic $q$ deformation on the Einstein's field equations and Friedmann equations. For this purpose, we represent the thermodynamical properties of the deformed…

General Relativity and Quantum Cosmology · Physics 2021-07-28 Mustafa Senay

This paper makes the simple observation that a fundamental length, or cutoff, in the context of Friedmann-Lema\^itre-Robertson-Walker (FRW) cosmology implies very different things than for a static universe. It is argued that it is…

Cosmology and Nongalactic Astrophysics · Physics 2011-01-13 Marvin Weinstein

Non-gravitational interaction between dark matter and dark energy has been considered in a spatially flat Friedmann-Lema\^{i}tre-Robertson-Walker (FLRW) universe. The interaction rate is assumed to be linear in the energy densities of dark…

General Relativity and Quantum Cosmology · Physics 2020-07-07 Supriya Pan , Jaume de Haro , Weiqiang Yang , Jaume Amorós

Modified gravity theories have the potential of explaining the recent acceleration of the Universe without resorting to the mysterious concept of dark energy. In particular, it has been pointed out that matter-geometry coupling may be…

General Relativity and Quantum Cosmology · Physics 2016-08-17 Min-Xing Xu , Tiberiu Harko , Shi-Dong Liang

Cosmology and astrophysics provide various ways to study the properties of dark matter even if they have negligible non-gravitational interactions with the Standard Model particles and remain hidden. We study a type of hidden dark matter…

Cosmology and Nongalactic Astrophysics · Physics 2025-06-03 Weikang Lin , Xingang Chen , Himanish Ganjoo , Liqiang Hou , Katherine J. Mack

We present a formalism for spatial averaging in cosmology applicable to general spacetimes and coordinates, and allowing the easy incorporation of a wide variety of matter sources. We apply this formalism to a…

General Relativity and Quantum Cosmology · Physics 2009-12-04 Iain A. Brown , Juliane Behrend , Karim A. Malik