Irreversible Geometrothermodynamics of Open Systems in Modified Gravity

Abstract

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 representation of $f(R,T)$ gravity, in which the matter energy-momentum tensor is not conserved due to a nonminimal curvature-matter coupling. In the context of the irreversible thermodynamics of open systems, this non-conservation of the energy-momentum tensor can be interpreted as an irreversible flow of energy from the gravitational sector to the matter sector, which, in general, could result in particle creation. We obtain and discuss the expressions for the particle creation rate, the creation pressure, and the entropy and temperature evolutions. Applied together with the modified field equations of scalar-tensor $f(R,T)$ gravity, the thermodynamics of open systems lead to a generalization of the $\Lambda$CDM cosmological paradigm, in which the particle creation rate and pressure are considered effectively as components of the cosmological fluid energy-momentum tensor. Thus, generally, modified theories of gravity in which these two quantities do not vanish provide a macroscopic phenomenological description of particle production in the cosmological fluid filling the Universe and also lead to the possibility of cosmological models that start from empty conditions and gradually build up matter and entropy.

17 pages; review article based on arXiv:2205.12545, arXiv:1508.02511 and arXiv:1408.3465. Published version in Entropy

References in corpus (13)

• f(R,T) gravity
• Extra force in $f(R)$ modified theories of gravity
• f(R,L_m) gravity
• Nonminimal coupling of perfect fluids to curvature
• $f(T,\mathcal{T})$ gravity and cosmology
• Generalized curvature-matter couplings in modified gravity
• Thermodynamic interpretation of the generalized gravity models with geometry - matter coupling
• Nonminimal torsion-matter coupling extension of f(T) gravity
• Non-exotic traversable wormhole solutions in linear $f\left(R,T\right)$ gravity
• Generalized dark gravity
• Gravitationally induced particle production in scalar-tensor $f(R,T)$ gravity
• Gravitationally Induced Particle Production through a Nonminimal Torsion-Matter Coupling
• Curvature-matter couplings in modified gravity: from linear models to conformally invariant theories

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• Energy-Momentum Squared Gravity: A Brief Overview
• Baryon asymmetry from higher-order matter contributions in gravity
• Thermodynamics of the Primordial Universe
• Regular black hole solutions in $(2+1)$-dimensional $f(R,T)$ gravity coupled to nonlinear electrodynamics
• Spin effects on particle creation and evaporation in $f(R,T)$ gravity
• On energy-momentum conservation in non-minimal geometry-matter coupling theories