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Geometrothermodynamics and Its Applications

A special issue of Entropy (ISSN 1099-4300). This special issue belongs to the section "Astrophysics, Cosmology, and Black Holes".

Deadline for manuscript submissions: closed (31 March 2024) | Viewed by 5993

Special Issue Editors


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Guest Editor
Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, AP 70543, Ciudad de México 04510, Mexico
Interests: general relativity; cosmology; thermodynamics; relativistic astrophysics
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Special Issue Information

Dear Colleagues,

Modern cosmological models are based upon the cosmological principle, which has by now been well confirmed by large-scale cosmic observations and background gravitational theory. To solve the corresponding field equations that govern the dynamics of the model, an additional ingredient is necessary, implying an ad hoc relationship between thermodynamic variables. Another possibility is to use geometrothermodynamics (GTD) to find fundamental thermodynamic equations that describe the universe as a thermodynamic system. This approach would essentially allow us to apply the laws of thermodynamics within a gravity theory to describe the universe’s evolution.

We would like to invite researchers to contribute articles on the applications of GTD, thermodynamic geometry, and classical thermodynamics in theoretical cosmology. Articles considering other aspects of the interplay between thermodynamics and gravity in cosmological configurations are also welcome.

Dr. Orlando Luongo
Dr. Hernando Quevedo
Guest Editors

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Published Papers (5 papers)

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Research

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12 pages, 419 KiB  
Article
Geometrothermodynamics of 3D Regular Black Holes
by Nurzada Beissen
Entropy 2024, 26(6), 457; https://doi.org/10.3390/e26060457 - 28 May 2024
Viewed by 592
Abstract
We investigate a spherically symmetric exact solution of Einstein’s gravity with cosmological constant in (2 + 1) dimensions, non-minimally coupled to a scalar field. The solution describes the gravitational field of a black hole, which is free of curvature singularities in the entire [...] Read more.
We investigate a spherically symmetric exact solution of Einstein’s gravity with cosmological constant in (2 + 1) dimensions, non-minimally coupled to a scalar field. The solution describes the gravitational field of a black hole, which is free of curvature singularities in the entire spacetime. We use the formalism of geometrothermodynamics to investigate the geometric properties of the corresponding space of equilibrium states and find their interpretation from the point of view of thermodynamics. It turns out that, as a result of the presence of thermodynamic interaction, the space of equilibrium states is curved with two possible configurations, which depend on the value of a coupling constant. In the first case, the equilibrium space is completely regular, corresponding to a stable thermodynamic system. The second case is characterized by the presence of two curvature singularities, which are shown to correspond to locations where the system undergoes two different phase transitions, one due to the breakdown of the thermodynamic stability condition and the second one due to the presence of a divergence at the level of the response functions. Full article
(This article belongs to the Special Issue Geometrothermodynamics and Its Applications)
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11 pages, 317 KiB  
Article
Stability Properties of Geometrothermodynamic Cosmological Models
by Nurzada Beissen, Medeu Abishev, Manas Khassanov, Temirbolat Aitassov, Sagira Mamatova and Saken Toktarbay
Entropy 2023, 25(10), 1391; https://doi.org/10.3390/e25101391 - 28 Sep 2023
Cited by 1 | Viewed by 883
Abstract
We consider a particular isotropic and homogeneous cosmological model, in which the equation of state is obtained from a thermodynamic fundamental equation by using the formalism of geometrothermodynamics (GTD). The model depends effectively on three arbitrary constants, which can be fixed to reproduce [...] Read more.
We consider a particular isotropic and homogeneous cosmological model, in which the equation of state is obtained from a thermodynamic fundamental equation by using the formalism of geometrothermodynamics (GTD). The model depends effectively on three arbitrary constants, which can be fixed to reproduce the main aspects of the inflationary era and the ΛCDM paradigm. We use GTD to analyze the geometric properties of the corresponding equilibrium space and to derive the stability properties and phase transition structure of the cosmological model. Full article
(This article belongs to the Special Issue Geometrothermodynamics and Its Applications)
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12 pages, 505 KiB  
Article
Holographic Dark Energy in Modified Barrow Cosmology
by Ahmad Sheykhi and Maral Sahebi Hamedan
Entropy 2023, 25(4), 569; https://doi.org/10.3390/e25040569 - 26 Mar 2023
Cited by 12 | Viewed by 1463
Abstract
Thermodynamics–gravity conjecture implies that there is a deep connection between the gravitational field equations and the first law of thermodynamics. Therefore, any modification to the entropy expression directly modifies the field equations. By considering the modified Barrow entropy associated with the apparent horizon, [...] Read more.
Thermodynamics–gravity conjecture implies that there is a deep connection between the gravitational field equations and the first law of thermodynamics. Therefore, any modification to the entropy expression directly modifies the field equations. By considering the modified Barrow entropy associated with the apparent horizon, the Friedmann equations are modified as well. In this paper, we reconsider the holographic dark energy (HDE) model when the entropy is in the form of Barrow entropy. This modification to the entropy not only changes the energy density of the HDE but also modifies the Friedmann equations. Therefore, one should take into account the modified HDE in the context of modified Friedmann equations. We study the Hubble horizon and the future event horizon as IR cutoffs and investigate the cosmological consequences of this model. We also extend our study to the case where dark matter (DM) and dark energy (DE) interact with each other. We observe that Barrow exponent δ significantly affects the cosmological behavior of HDE, and in particular, the equation of state (EoS) parameter can cross the phantom line (wde<1). Additionally, adding δ remarkably affects the deceleration parameter and shifts the time of universe phase transition. Full article
(This article belongs to the Special Issue Geometrothermodynamics and Its Applications)
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Review

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22 pages, 380 KiB  
Review
Geometrothermodynamic Cosmology
by Orlando Luongo and Hernando Quevedo
Entropy 2023, 25(7), 1037; https://doi.org/10.3390/e25071037 - 10 Jul 2023
Cited by 4 | Viewed by 1151
Abstract
We review the main aspects of geometrothermodynamics, a formalism that uses contact geometry and Riemannian geometry to describe the properties of thermodynamic systems. We show how to handle in a geometric way the invariance of classical thermodynamics with respect to Legendre transformations, which [...] Read more.
We review the main aspects of geometrothermodynamics, a formalism that uses contact geometry and Riemannian geometry to describe the properties of thermodynamic systems. We show how to handle in a geometric way the invariance of classical thermodynamics with respect to Legendre transformations, which means that the properties of the systems do not depend on the choice of the thermodynamic potential. Moreover, we show that, in geometrothermodynamics, it is possible to apply a variational principle to generate thermodynamic fundamental equations, which can be used in the context of relativistic cosmology to generate cosmological models. As a particular example, we consider a fundamental equation that relates the entropy with the internal energy and the volume of the Universe, and construct cosmological models with arbitrary parameters, which can be fixed to reproduce the main aspects of the inflationary era and the standard cosmological paradigm. Full article
(This article belongs to the Special Issue Geometrothermodynamics and Its Applications)
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17 pages, 338 KiB  
Review
Irreversible Geometrothermodynamics of Open Systems in Modified Gravity
by Miguel A. S. Pinto, Tiberiu Harko and Francisco S. N. Lobo
Entropy 2023, 25(6), 944; https://doi.org/10.3390/e25060944 - 15 Jun 2023
Cited by 2 | Viewed by 1032
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 [...] Read more.
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 ΛCDM 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. Full article
(This article belongs to the Special Issue Geometrothermodynamics and Its Applications)
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