Generalized Second Law and Thermodynamical Aspects of $f(Q,\mathcal{T})$ Gravity

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Main Authors: Pradhan, Anirudh, Husain, A., Zeyauddin, M., Shekh, S. H.
Format: Preprint
Published: 2025
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author Pradhan, Anirudh
Husain, A.
Zeyauddin, M.
Shekh, S. H.
author_facet Pradhan, Anirudh
Husain, A.
Zeyauddin, M.
Shekh, S. H.
contents Late-time cosmic acceleration has motivated the exploration of various extensions of general relativity, among which $f(Q,\mathcal{T})$ gravity, based on the non-metricity scalar $Q$ and the trace of the energy--momentum tensor $\mathcal{T}$, has gained increasing attention. In this study, we explore the thermodynamic aspects of $f(Q,\mathcal{T})$ gravity by establishing the first law and generalized second law of thermodynamics at the apparent horizon of a flat FLRW universe. By applying the Gibbs relation, we determined the rate of change of the total entropy and assessed the conditions under which the generalized second law remains valid for various choices of $f(Q,\mathcal{T})$. Our analysis focuses on linear, power-law, quadratic trace, exponential, and cross-coupling models, inspired by frameworks such as $f(R,\mathcal{T})$, $f(T)$, and modifications motivated by string theory. Our analysis showed that linear and mildly nonlinear models are generally thermodynamically consistent, whereas strongly nonlinear or interaction-type models require fine-tuned parameters for the generalized second law to hold. The present analysis underscores that thermodynamic considerations serve as effective criteria for assessing the viability of modified gravity models and their relevance to cosmological dynamics.
format Preprint
id arxiv_https___arxiv_org_abs_2510_12863
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Generalized Second Law and Thermodynamical Aspects of $f(Q,\mathcal{T})$ Gravity
Pradhan, Anirudh
Husain, A.
Zeyauddin, M.
Shekh, S. H.
General Relativity and Quantum Cosmology
Late-time cosmic acceleration has motivated the exploration of various extensions of general relativity, among which $f(Q,\mathcal{T})$ gravity, based on the non-metricity scalar $Q$ and the trace of the energy--momentum tensor $\mathcal{T}$, has gained increasing attention. In this study, we explore the thermodynamic aspects of $f(Q,\mathcal{T})$ gravity by establishing the first law and generalized second law of thermodynamics at the apparent horizon of a flat FLRW universe. By applying the Gibbs relation, we determined the rate of change of the total entropy and assessed the conditions under which the generalized second law remains valid for various choices of $f(Q,\mathcal{T})$. Our analysis focuses on linear, power-law, quadratic trace, exponential, and cross-coupling models, inspired by frameworks such as $f(R,\mathcal{T})$, $f(T)$, and modifications motivated by string theory. Our analysis showed that linear and mildly nonlinear models are generally thermodynamically consistent, whereas strongly nonlinear or interaction-type models require fine-tuned parameters for the generalized second law to hold. The present analysis underscores that thermodynamic considerations serve as effective criteria for assessing the viability of modified gravity models and their relevance to cosmological dynamics.
title Generalized Second Law and Thermodynamical Aspects of $f(Q,\mathcal{T})$ Gravity
topic General Relativity and Quantum Cosmology
url https://arxiv.org/abs/2510.12863