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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

We explore the possibility of gravitationally generated particle production in the scalar-tensor representation of $f(R,T)$ gravity. Due to the explicit nonminimal curvature-matter coupling in the theory, the divergence of the matter…

General Relativity and Quantum Cosmology · Physics 2022-09-02 Miguel A. S. Pinto , Tiberiu Harko , Francisco S. N. Lobo

Modified gravity theories with a nonminimal coupling between curvature and matter offer a compelling alternative to dark energy and dark matter by introducing an explicit interaction between matter and curvature invariants. Two of the main…

General Relativity and Quantum Cosmology · Physics 2025-10-29 Francisco S. N. Lobo , Tiberiu Harko , Miguel A. S. Pinto

An interesting cosmological history was proposed by Prigogine {\it et al.} who considered the Universe as a thermodynamically open system. This scenario is characterized by a process of matter creation, which corresponds to an irreversible…

General Relativity and Quantum Cosmology · Physics 2015-08-14 Francisco S. N. Lobo , Tiberiu Harko , José P. Mimoso , Diego Pavón

In this work, we explore the formalism of the irreversible thermodynamics of open systems and the possibility of gravitationally generated particle production in modified gravity. More specifically, we consider the scalar-tensor…

General Relativity and Quantum Cosmology · Physics 2023-06-27 Miguel A. S. Pinto , Tiberiu Harko , Francisco S. N. Lobo

In this proceeding, we review modified theories of gravity with a curvature-matter coupling between an arbitrary function of the scalar curvature and the Lagrangian density of matter. This explicit nonminimal coupling induces a…

General Relativity and Quantum Cosmology · Physics 2022-09-20 Francisco S. N. Lobo , Tiberiu Harko

In this work, we analyze the possibility of gravitationally induced matter creation in the so-called Energy-Momentum-Squared gravity (EMSG), i.e. $f(R,T_{\mu\nu}T^{\mu\nu})$ gravity, in its dynamically equivalent scalar-tensor…

General Relativity and Quantum Cosmology · Physics 2024-03-15 Ricardo A. C. Cipriano , Tiberiu Harko , Francisco S. N. Lobo , Miguel A. S. Pinto , João Luís Rosa

In extended models of gravity a nonminimal coupling to matter has been assumed to lead to irreversible particle creation. In this paper we challenge this assumption. We argue that a non-minimal coupling of the matter and gravitational…

General Relativity and Quantum Cosmology · Physics 2019-04-02 R. P. L. Azevedo , P. P. Avelino

Modified gravity theories with geometry - matter coupling, in which the action is an arbitrary function of the Ricci scalar and the matter Lagrangian ($f\left(R,L_m\right)$ gravity), and of the Ricci scalar and of the trace of the matter…

General Relativity and Quantum Cosmology · Physics 2015-06-22 Tiberiu Harko

A relativistic kinetic description for the irreversible thermodynamic process of gravitationally induced particle production is proposed in the context of an expanding Friedmann-Robertson-Walker (FRW) geometry. We show that the covariant…

General Relativity and Quantum Cosmology · Physics 2014-11-25 J. A. S. Lima , I. P. Baranov

A macroscopic and kinetic relativistic description for a decoupled multi-fluid cosmology endowed with gravitationally induced particle production of all components is proposed. The temperature law for each decoupled particle species is also…

Cosmology and Nongalactic Astrophysics · Physics 2023-04-12 S. R. G. Trevisani , J. A. S. Lima

The Hubble tension and the unknown origin of dark energy motivate the exploration of alternative mechanisms for late-time cosmic acceleration. We investigate gravitationally induced particle creation (PC) as a non-equilibrium process that…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-28 Tiziano Schiavone , Mariaveronica De Angelis , Luis A. Escamilla , Giovanni Montani , Eleonora Di Valentino

We attempt to construct a gravitational coupling by pre-selecting an energy-momentum tensor as the source for gravitational field. The energy-momentum tensor we take is a recently derived new expression motivated by joint localization of…

General Relativity and Quantum Cosmology · Physics 2017-02-10 Tao Lei , Zi-Wei Chen , Zhen-Lai Wang , Xiang-Song Chen

The paper deals with the mechanism of particle creation in the framework of irreversible thermodynamics. The second order non-equilibrium thermodynamical prescription of Israel and Stewart has been presented with particle creation rate,…

General Relativity and Quantum Cosmology · Physics 2016-05-04 Subenoy Chakraborty , Subhajit Saha

We consider an extension of standard General Relativity in which the Hilbert-Einstein action is replaced by an arbitrary function of the Ricci scalar, nonmetricity, torsion, and the trace of the matter energy-momentum tensor. By…

General Relativity and Quantum Cosmology · Physics 2024-11-18 Tiberiu Harko , Nurgissa Myrzakulov , Ratbay Myrzakulov , Shahab Shahidi

Gravitational particle production has been investigated by using Einstein's gravitational field equations in the presence of a cosmological constant. To study the mechanism of particle creation, the Universe has been considered as a…

General Relativity and Quantum Cosmology · Physics 2020-04-07 Z. Safari , B. Malekolkalami , H. Moshafi

Dark photons are a theorized massive spin-1 particle which can be produced via various mechanisms, including cosmological gravitational particle production (GPP) in the early universe. In this work, we extend previous results for GPP of…

High Energy Physics - Theory · Physics 2024-09-20 Christian Capanelli , Leah Jenks , Edward W. Kolb , Evan McDonough

With the help of a conformal, timelike Killing-vector we define generalized equilibrium states for cosmological fluids with particle production. For massless particles the generalized equilibrium conditions require the production rate to…

General Relativity and Quantum Cosmology · Physics 2009-10-30 Winfried Zimdahl

The present work deals with a cosmological model having particle creation mechanism in the framework of irreversible thermodynamics. In the second order non-equilibrium thermodynamical prescription, the particle creation rate is treated as…

General Relativity and Quantum Cosmology · Physics 2015-05-01 Subenoy Chakraborty , Supriya Pan , Subhajit Saha

We study particle production and the corresponding entropy increase in the context of cosmology with dynamical vacuum. We focus on the particular form that has been called "running vacuum model" (RVM), which is known to furnish a successful…

General Relativity and Quantum Cosmology · Physics 2020-02-14 Joan Sola , Hao Yu
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