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The linear and quadratic perturbations for a scalar-tensor model with non-minimal coupling to curvature, coupling to the Gauss-Bonnet invariant and non-minimal kinetic coupling to the Einstein tensor are developed. The quadratic action for…

General Relativity and Quantum Cosmology · Physics 2019-09-24 L. N. Granda , D. F. Jimenez

We discuss Einstein gravity for a fluid consisting of particles interacting with an unidentified environment of some other particles whose dissipative effect is approximated by a diffusion. The environment is described by a time dependent…

General Relativity and Quantum Cosmology · Physics 2015-06-16 Z. Haba

A system of field equations for an Einstein-Maxwell model with $RF^2$-type nonminimal coupling in a non-Riemannian space-time with a non-vanishing torsion is derived and the resulting field equations are expressed in terms of the Riemannian…

General Relativity and Quantum Cosmology · Physics 2015-10-28 Ahmet Baykal , Tekin Dereli

It is a fundamental problem in mathematical physics to derive macroscopic transport equations from microscopic models. In this paper we derive the linear Boltzmann equation in the low-density limit of a damped quantum Lorentz gas for a…

Mathematical Physics · Physics 2023-03-29 Jory Griffin

Boltzmann equation describes the time development of the velocity distribution in the continuum fluid matter. We formulate the equation using the field theory where the {\it velocity-field} plays the central role. The matter (constituent…

High Energy Physics - Theory · Physics 2013-10-10 Shoichi Ichinose

We give a brief review of the non-minimal derivative coupling (NMDC) scalar field theory in which there is non-minimal coupling between the scalar field derivative term and the Einstein tensor. We assume that the expansion is of power-law…

General Relativity and Quantum Cosmology · Physics 2020-01-14 Burin Gumjudpai , Phongsaphat Rangdee

We prove that solutions to the Boltzmann equation without cut-off satisfying pointwise bounds on some observables (mass, pressure, and suitable moments) enjoy a uniform bound in $L^\infty$ in the case of hard potentials. As a consequence,…

Analysis of PDEs · Mathematics 2025-06-13 Xavier Fernández-Real , Xavier Ros-Oton , Marvin Weidner

The non-abelian Einstein-Born-Infeld-Dilaton theory, which rules the dynamics of tensor-scalar gravitation coupled to a $su(2)$-valued gauge field ruled by Born-Infeld lagrangian, is studied in a cosmological framework. The microscopic…

General Relativity and Quantum Cosmology · Physics 2011-07-19 A. Fuzfa , J. -M. Alimi

We consider a non-minimal coupling of a perfect fluid matter system with geometry, which the coupling function is taken to be an arbitrary function of the Ricci scalar. Due to such a coupling, the matter stress tensor is no longer conserved…

General Relativity and Quantum Cosmology · Physics 2015-06-16 Yousef Bisabr

We study inflationary scenarios driven by a scalar field in the presence of a non-minimal coupling between matter and curvature. We show that the Friedmann equation can be significantly modified when the energy density during inflation…

General Relativity and Quantum Cosmology · Physics 2017-06-28 Cláudio Gomes , João G. Rosa , Orfeu Bertolami

This paper proves the existence of weak solutions to the spatially homogeneous Boltzmann equation for Maxwellian molecules, when the initial data are chosen from the space of all Borel probability measures on R^3 with finite second moments…

Mathematical Physics · Physics 2013-06-24 Emanuele Dolera

We argue that one can model deviations from the ensemble average in non-equilibrium statistical mechanics by promoting the Boltzmann equation to an equation in terms of {\em functionals} , representing possible candidates for phase space…

Statistical Mechanics · Physics 2024-03-13 Giorgio Torrieri

We review the study of inhomogeneous perturbations about a homogeneous and isotropic background cosmology. We adopt a coordinate based approach, but give geometrical interpretations of metric perturbations in terms of the expansion, shear…

Astrophysics · Physics 2010-04-23 Karim A. Malik , David Wands

A kinetic theory for relativistic gases in the presence of gravitational fields is developed in the second post-Newtonian approximation. The corresponding Boltzmann equation is determined from the evolution of the one-particle distribution…

General Relativity and Quantum Cosmology · Physics 2021-02-04 Gilberto M. Kremer

The conservation law for the angular momentum in curved spacetime, consistent with relativistic quantum mechanics, requires that the antisymmetric part of the affine connection (torsion tensor) is a variable in the principle of least…

General Relativity and Quantum Cosmology · Physics 2026-05-28 Nikodem Popławski

We show that in modified $f(R)$ type gravity models with non-minimal coupling between matter and geometry, both the matter Lagrangian, and the energy-momentum tensor, are completely and uniquely determined by the form of the coupling. This…

General Relativity and Quantum Cosmology · Physics 2010-05-27 T. Harko

Horndeski derived a most general vector-tensor theory in which the vector field respects the gauge symmetry and the resulting dynamical equations are of second order. The action contains only one free parameter, $\lambda$, that determines…

General Relativity and Quantum Cosmology · Physics 2013-03-12 John D. Barrow , Mikjel Thorsrud , Kei Yamamoto

The scalar-tensor representation of $f(R,T)$ gravity is extended to incorporate the Herglotz variational principle. The field equations are derived in both the geometric and scalar-tensor frameworks. Although the divergence of the…

General Relativity and Quantum Cosmology · Physics 2026-03-02 Marek Wazny

We show a curvaton model, in which the curvaton has a nonminimal derivative coupling to gravity. Thanks to such a coupling, we find that the scale-invariance of the perturbations can be achieved for arbitrary values of the equation-of-state…

High Energy Physics - Theory · Physics 2015-06-16 Kaixi Feng , Taotao Qiu , Yun-Song Piao

We show that in the $f(Q)$ gravity with a non-metricity scalar $Q$, the curvatures in Einstein's gravity, that is, the Riemann curvature constructed from the standard Levi-Civita connection, could not be excluded or naturally appear. The…

General Relativity and Quantum Cosmology · Physics 2024-08-16 Shin'ichi Nojiri , S. D. Odintsov