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In this paper we demonstrate that Boltzmann's $H$-theorem does not necessarily hold in the context of theories of gravity with nonminimally coupled matter fields. We find sufficient conditions for the violation of Boltzmann's $H$-theorem…

General Relativity and Quantum Cosmology · Physics 2020-07-29 P. P. Avelino , R. P. L. Azevedo

In this note we comment on remarks about our recent effort to understand the specificities of the Boltzmann equation in the context of the alternative theories of gravity with non-minimal coupling between curvature and matter.

General Relativity and Quantum Cosmology · Physics 2020-05-11 Orfeu Bertolami , Cláudio Gomes

A dynamical estimate is given for the Boltzmann entropy of the Universe, under the simplifying assumptions provided by Newtonian cosmology. We first model the cosmological fluid as the probability fluid of a quantum-mechanical system. Next,…

Quantum Physics · Physics 2023-07-19 D. Cabrera , P. Fernandez de Cordoba , J. M. Isidro

In this work we adapt the foundations of relativistic kinetic theory and the Boltzmann equation to particles with Lorentz-violating dispersion relations. The latter are taken to be those associated to two commonly considered sets of…

Statistical Mechanics · Physics 2022-12-14 Robertus Potting

In this letter we study the behavior of non-minimally coupled Einstein-Gauss-Bonnet gravity theories with the constant-roll condition. Recalling the results of the striking GW170817 event, we demand that the velocity of the gravitational…

General Relativity and Quantum Cosmology · Physics 2020-11-10 V. K. Oikonomou , F. P. Fronimos

We present a general formulation of the theory for a non-minimally coupled perfect fluid in which both conformal and disformal couplings are present. We discuss how such non-minimal coupling is compatible with the assumptions of a perfect…

General Relativity and Quantum Cosmology · Physics 2015-10-20 Dario Bettoni , Stefano Liberati

The Boltzmann equation is a nonlinear partial differential equation that plays a central role in statistical mechanics. From the mathematical point of view, the existence of global smooth solutions for arbitrary initial data is an…

Analysis of PDEs · Mathematics 2020-11-25 Cyril Imbert , Luis Silvestre

We consider f(R,T) modified theory of gravity in which, in general, the gravitational Lagrangian is given by an arbitrary function of the Ricci scalar and the trace of the energy-momentum tensor. We indicate that in this type of the theory,…

General Relativity and Quantum Cosmology · Physics 2016-10-05 Raziyeh Zaregonbadi , Mehrdad Farhoudi

We consider a gravitational theory with an additional non-minimal coupling between baryonic matter fields and geometry. The coupling is second order in the energy momentum tensor and can be seen as a generalization of the energy-momentum…

General Relativity and Quantum Cosmology · Physics 2021-04-19 Shahab Shahidi

The equations governing the evolution of non-minimally coupled scalar matter and the scale factor of a Robertson-Walker universe are derived from a minisuperspace action. As for the minimally coupled case, it is shown that the entire…

General Relativity and Quantum Cosmology · Physics 2009-10-31 G. L. Alberghi , R. Casadio , A. Gruppuso

We consider the possibility of a gravitationally induced particle production through the mechanism of a nonminimal curvature-matter coupling. An interesting feature of this gravitational theory is that the divergence of the energy-momentum…

General Relativity and Quantum Cosmology · Physics 2015-08-31 Tiberiu Harko , Francisco S. N. Lobo , José P. Mimoso , Diego Pavón

In certain modified theories of gravity, non-minimal couplings between matter and geometry lead to the nonconservation of the energy-momentum tensor. By interpreting this as an effective dissipative process, we formulate a general class of…

General Relativity and Quantum Cosmology · Physics 2026-04-27 Szőllősi Tamás-Géza

We consider the Einstein-Boltzmann system for massless particles in the Bianchi I space-time with scattering cross-sections in a certain range of soft potentials. We assume that the space-time has an initial conformal gauge singularity and…

General Relativity and Quantum Cosmology · Physics 2024-08-21 Ho Lee , Ernesto Nungesser , John Stalker , Paul Tod

It is known that the singularity in the non-cutoff cross-section of the Boltzmann equation leads to the gain of regularity and gain of weight in the velocity variable. By defining and analyzing a non-isotropy norm which precisely captures…

Analysis of PDEs · Mathematics 2010-10-28 Radjesvarane Alexandre , Yoshinori Morimoto , Seiji Ukai , Chao-Jiang Xu , Tong Yang

We evaluate the entanglement entropy of a non-minimal coupling Einstein-scalar theory with two approaches in classical Euclidean gravity. By analysing the equation of motion, we find that the entangled surface is restricted to be a minimal…

High Energy Physics - Theory · Physics 2016-06-29 Bing Sun , Weizhen Jia , Xingyang Yu

The coupling of the electromagnetic field to gravity is an age-old problem. Presently, there is a resurgence of interest in it, mainly for two reasons: (i) Experimental investigations are under way with ever increasing precision, be it in…

General Relativity and Quantum Cosmology · Physics 2016-12-07 Friedrich W. Hehl , Yuri N. Obukhov

This is the first one of two papers on the global dynamics of the original Boltzmann equations without angular cutoff on the torus. We address the problem for the hard potentials and Maxwellian molecules in the present paper. The case of…

Analysis of PDEs · Mathematics 2017-12-18 Ling-Bing He , Jin-Cheng Jiang

We explore a cosmological model in which dark matter is non-minimally coupled to gravity at the fluid level. While typically subdominant compared to Standard Model forces, such couplings may dominate dark matter dynamics. We show that this…

General Relativity and Quantum Cosmology · Physics 2025-10-14 Samuele Silveravalle , Andrea Lapi , Francesco Benetti , Stefano Liberati

It is generally believed that coupling the graviton (a classical Fierz-Pauli massless spin-2 field) to its own energy-momentum tensor successfully recreates the dynamics of the Einstein field equations order by order; however the validity…

General Relativity and Quantum Cosmology · Physics 2009-10-29 Luke M. Butcher , Michael Hobson , Anthony Lasenby

We use a macroscopic description of a system of relativistic particles based on adding a nonequilibrium tensor to the usual hydrodynamic variables. The nonequilibrium tensor is linked to relativistic kinetic theory through a nonlinear…

Nuclear Theory · Physics 2015-06-12 J. Peralta-Ramos , E. Calzetta
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