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We develop a class of matrix models which implement and formalize the `eigenstate thermalization hypothesis' (ETH) and point out that in general these models must contain non-Gaussian corrections, already in order to correctly capture…

High Energy Physics - Theory · Physics 2023-01-06 Daniel Louis Jafferis , David K. Kolchmeyer , Baur Mukhametzhanov , Julian Sonner

We present a $f(G,T)$ gravity-based reconstruction of Barrow Holographic Dark Energy (BHDE). This approach extends the conventional HDE model by replacing the Bekenstein-Hawking entropy with Barrow entropy, which encapsulates quantum…

General Relativity and Quantum Cosmology · Physics 2025-05-29 Giuseppe Gaetano Luciano

We consider quantum algebras of observables associated with subregions in theories of Einstein gravity coupled to matter in the $G_N\rightarrow 0$ limit. When the subregion is spatially compact or encompasses an asymptotic boundary, we…

High Energy Physics - Theory · Physics 2024-02-07 Kristan Jensen , Jonathan Sorce , Antony Speranza

In this study, we present constraints on the parameters of three well-known $f(R)$ gravity models, viz. (i) Hu-Sawicki, (ii) Starobinsky, and (iii) ArcTanh by using a joint analysis of recent cosmological observations. We perform analytical…

Cosmology and Nongalactic Astrophysics · Physics 2025-06-30 Darshan Kumar , Praveen Kumar Dhankar , Saibal Ray , Fengge Zhang

In this paper we study the viability of an entropic cosmological model. The effects of entropic gravity are derived from a modified entropy-area relationship with a volumetric entropy term. This model describes a late time limit cosmic…

General Relativity and Quantum Cosmology · Physics 2024-03-07 Javier Chagoya , I. Díaz-Saldaña , J. C. López-Domínguez , M. Sabido

The present work deals with a detailed study of universal thermodynamics in different modified gravity theories. The validity of the generalized second law of thermodynamics (GSLT) and thermodynamical equilibrium (TE) of the Universe…

General Relativity and Quantum Cosmology · Physics 2016-11-02 Saugata Mitra , Subhajit Saha , Subenoy Chakraborty

In this paper, the generalized second law (GSL) of thermodynamics and entropy is revisited in the context of cosmological models in Gauss-Bonnet gravity with the boundary of the universe is assumed to be enclosed by the dynamical apparent…

General Relativity and Quantum Cosmology · Physics 2015-06-03 Hossein Farajollahi , Amin Salehi

We develop a geometric realization of a broad class of generalized black hole entropy functionals by establishing their direct correspondence with the Misner$-$Sharp quasilocal mass and the Wald Noether$-$charge entropy in scalar$-$tensor…

General Relativity and Quantum Cosmology · Physics 2026-05-19 Hussain Gohar

In this paper, Gaussianity of eigenmodes and non-Gaussianity in the Cosmic Microwave Background (CMB) temperature fluctuations in two smallest compact hyperbolic (CH) models are investigated. First, it is numerically found that the…

Astrophysics · Physics 2009-12-30 Kaiki Taro Inoue

We study the geometric distribution of the relative entropy of a charged localised state in Quantum Field Theory. With respect to translations, the second derivative of the vacuum relative entropy is zero out of the charge localisation…

High Energy Physics - Theory · Physics 2019-02-20 Roberto Longo

We comment on the recent paper by Ghosh and \v{Z}nidari\v{c} (Phys. Rev. B 105, 144203 (2022)) which studies the growth of the number entropy $S_N$ in the Heisenberg model with random magnetic fields after a quantum quench. The authors…

Disordered Systems and Neural Networks · Physics 2022-06-22 Maximilian Kiefer-Emmanouilidis , Razmik Unanyan , Michael Fleischhauer , Jesko Sirker

We investigate the possibility of discrete groups furnishing a kinematic framework for systems whose thermodynamic behaviour may be given by non-additive entropies. Relying on the well-known result of the growth rate of balls of nilpotent…

Statistical Mechanics · Physics 2015-06-19 Nikos Kalogeropoulos

We consider several low--dimensional chaotic maps started in far-from-equilibrium initial conditions and we study the process of relaxation to equilibrium. In the case of conservative maps the Boltzmann-Gibbs entropy S(t) increases linearly…

Statistical Mechanics · Physics 2007-05-23 M. Baranger , V. Latora , A. Rapisarda

The present paper deals with the dynamics of spatially flat Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model with a time varying cosmological constant $\Lambda$ where $\Lambda$ evolves with the cosmic time (t) through the…

General Relativity and Quantum Cosmology · Physics 2022-10-19 Chingtham Sonia , S. Surendra Singh

The scale invariance of the universe is slightly broken by slow roll parameters. It is likely the slow roll is dual to the random walk. We investigate the distribution function of the conformal zeromode. We identify de Sitter entropy…

High Energy Physics - Theory · Physics 2022-06-16 Yoshihisa Kitazawa

We are concerned with spherically symmetric solutions to the Euler equations for the multi-dimensional compressible fluids, which have many applications in diverse real physical situations. The system can be reduced to one dimensional…

Analysis of PDEs · Mathematics 2019-08-20 Feimin Huang , Tianhong Li , Difan Yuan

To find more deliberate f(R,T) cosmological solutions, we proceed our previous paper further by studying some new aspects of the considered models via investigation of some new cosmological parameters/quantities to attain the most…

General Relativity and Quantum Cosmology · Physics 2017-05-23 Hamid Shabani , Mehrdad Farhoudi

We derive a general approximate solution to the problem of minimizing the conditional entropy of a qudit-qubit system resulting from a local projective measurement on the qubit, which is valid for general entropic forms and becomes exact in…

Quantum Physics · Physics 2015-06-22 N. Gigena , R. Rossignoli

The features of the fundamental thermodynamical relation (expressing entropy as function of state variables) that arise from the self-gravitating character of a system are analyzed. The models studied include not only a spherically…

General Relativity and Quantum Cosmology · Physics 2009-10-28 Erik A. Martinez

We investigate the properties of the FLRW flat cosmological models in which the vacuum energy density evolves with time, $\Lambda(t)$. Using different versions of the $\Lambda(t)$ model, namely quantum field vacuum, power series vacuum and…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 S. Basilakos , M. Plionis , J. Sola