Thermodynamics of an universe with decaying cold dark matter

Abstract In this work we focus on the thermodynamics consistency of a new set of solutions emerging from a cosmology in which dark matter is able to decay into relativistic particles within the dark sector. It is important to stress that the lifetime of dark matter is larger than the age of the univ...

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Main Authors: Javier Juárez-Jiménez, Ana A. Avilez-López, Miguel Cruz
Format: Article
Language:English
Published: SpringerOpen 2025-07-01
Series:European Physical Journal C: Particles and Fields
Online Access:https://doi.org/10.1140/epjc/s10052-025-14465-7
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author Javier Juárez-Jiménez
Ana A. Avilez-López
Miguel Cruz
author_facet Javier Juárez-Jiménez
Ana A. Avilez-López
Miguel Cruz
author_sort Javier Juárez-Jiménez
collection DOAJ
description Abstract In this work we focus on the thermodynamics consistency of a new set of solutions emerging from a cosmology in which dark matter is able to decay into relativistic particles within the dark sector. It is important to stress that the lifetime of dark matter is larger than the age of the universe in order to be consistent with observations. Given that the corresponding decay rate is small, this one can be used as a perturbative parameter and it is possible to construct analytic solutions from a perturbative analysis for the densities of the species and the scale factor. The decay of dark matter is an irreversible process since it occurs out of chemical equilibrium and therefore the entropy per comoving volume increases considerably, as a consequence the temperature does not scale as $$a^{-1}$$ a - 1 in contrast to an adiabatic expansion. We take into account two scenarios: a) The case in which both species making up the fluid end up in thermal equilibrium and therefore their temperature is the same. b) A second instance in which the species do not reach thermal equilibrium and therefore they have different temperatures. We verify that the second law of thermodynamics is satisfied in any case.
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spelling doaj-art-cc8dc6ad9b0540a2aa9cb03f12a692ea2025-08-20T03:04:17ZengSpringerOpenEuropean Physical Journal C: Particles and Fields1434-60522025-07-018571810.1140/epjc/s10052-025-14465-7Thermodynamics of an universe with decaying cold dark matterJavier Juárez-Jiménez0Ana A. Avilez-López1Miguel Cruz2Facultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de PueblaFacultad de Ciencias Físico Matemáticas, Benemérita Universidad Autónoma de PueblaFacultad de Física, Universidad VeracruzanaAbstract In this work we focus on the thermodynamics consistency of a new set of solutions emerging from a cosmology in which dark matter is able to decay into relativistic particles within the dark sector. It is important to stress that the lifetime of dark matter is larger than the age of the universe in order to be consistent with observations. Given that the corresponding decay rate is small, this one can be used as a perturbative parameter and it is possible to construct analytic solutions from a perturbative analysis for the densities of the species and the scale factor. The decay of dark matter is an irreversible process since it occurs out of chemical equilibrium and therefore the entropy per comoving volume increases considerably, as a consequence the temperature does not scale as $$a^{-1}$$ a - 1 in contrast to an adiabatic expansion. We take into account two scenarios: a) The case in which both species making up the fluid end up in thermal equilibrium and therefore their temperature is the same. b) A second instance in which the species do not reach thermal equilibrium and therefore they have different temperatures. We verify that the second law of thermodynamics is satisfied in any case.https://doi.org/10.1140/epjc/s10052-025-14465-7
spellingShingle Javier Juárez-Jiménez
Ana A. Avilez-López
Miguel Cruz
Thermodynamics of an universe with decaying cold dark matter
European Physical Journal C: Particles and Fields
title Thermodynamics of an universe with decaying cold dark matter
title_full Thermodynamics of an universe with decaying cold dark matter
title_fullStr Thermodynamics of an universe with decaying cold dark matter
title_full_unstemmed Thermodynamics of an universe with decaying cold dark matter
title_short Thermodynamics of an universe with decaying cold dark matter
title_sort thermodynamics of an universe with decaying cold dark matter
url https://doi.org/10.1140/epjc/s10052-025-14465-7
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AT miguelcruz thermodynamicsofanuniversewithdecayingcolddarkmatter