Non-minimal fluid Lagrangian couplings

Fuente: arXiv
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Main Authors: Boehmer, Christian G., Jensko, Erik, Al-Nasrallah, Eissa
Format: Preprint
Published: 2026
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author Boehmer, Christian G.
Jensko, Erik
Al-Nasrallah, Eissa
author_facet Boehmer, Christian G.
Jensko, Erik
Al-Nasrallah, Eissa
contents Gravitational models with non-minimal couplings involving functions of the matter Lagrangian and curvature have become popular in recent decades. By coupling the matter Lagrangian directly to the gravitational Lagrangian, one hopes to construct theories that can explain dark energy or dark matter without introducing additional sources. When this matter Lagrangian describes a perfect fluid, some technicalities are involved in its variational formulation. We present a careful derivation of the gravitational field equations together with the complete set of fluid equations. The fluid's equations allow us to define thermodynamic quantities such as temperature, chemical potential and number density and thus allow us to understand the effects of the non-minimal couplings on these quantities. We demonstrate the non-equivalence of the Lagrangian formulations of Schutz and Brown for these types of models and provide a detailed interpretation of our results.
format Preprint
id arxiv_https___arxiv_org_abs_2605_16220
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Non-minimal fluid Lagrangian couplings
Boehmer, Christian G.
Jensko, Erik
Al-Nasrallah, Eissa
General Relativity and Quantum Cosmology
Mathematical Physics
Gravitational models with non-minimal couplings involving functions of the matter Lagrangian and curvature have become popular in recent decades. By coupling the matter Lagrangian directly to the gravitational Lagrangian, one hopes to construct theories that can explain dark energy or dark matter without introducing additional sources. When this matter Lagrangian describes a perfect fluid, some technicalities are involved in its variational formulation. We present a careful derivation of the gravitational field equations together with the complete set of fluid equations. The fluid's equations allow us to define thermodynamic quantities such as temperature, chemical potential and number density and thus allow us to understand the effects of the non-minimal couplings on these quantities. We demonstrate the non-equivalence of the Lagrangian formulations of Schutz and Brown for these types of models and provide a detailed interpretation of our results.
title Non-minimal fluid Lagrangian couplings
topic General Relativity and Quantum Cosmology
Mathematical Physics
url https://arxiv.org/abs/2605.16220