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A novel fractal structure for the cosmological horizon, inspired by COVID-19 geometry, which results in a modified area entropy, is applied to cosmology in order to serve dark energy. The constraints based on a complete set of observational…

Cosmology and Nongalactic Astrophysics · Physics 2020-09-18 Mariusz P. Dabrowski , Vincenzo Salzano

We develop a non-extensive thermodynamic framework for Reissner--Nordstr\"om black holes based on a near-horizon photon-gas model within Tsallis statistics. We derive the generalized Bekenstein--Hawking entropy based on such an approach,…

General Relativity and Quantum Cosmology · Physics 2026-05-13 Phuwadon Chunaksorn , Ratchaphat Nakarachinda , Pitayuth Wongjun

In the realm of thermodynamics of apparent horizon, we construct a dark energy (DE) model from 4-parameter generalized entropy of apparent horizon in a spatially non-flat universe. In particular, considering a non-zero spatial curvature of…

General Relativity and Quantum Cosmology · Physics 2025-04-07 Sergei D. Odintsov , Simone D'Onofrio , Tanmoy Paul

In this paper, we study thermodynamical properties of the apparent horizon in a universe governed by quasi-topological gravity. Our aim is twofold. First, by using the variational method we derive the general form of Friedmann equation in…

High Energy Physics - Theory · Physics 2015-06-16 M. H. Dehghani , A. Sheykhi , R. Dehghani

We construct new classes of modified theories in which the matter sector couples with the Einstein tensor, namely we consider direct couplings of the latter to the energy-momentum tensor, and to the derivatives of its trace. We extract the…

General Relativity and Quantum Cosmology · Physics 2023-05-17 Petros Asimakis , Spyros Basilakos , Andreas Lymperis , Maria Petronikolou , Emmanuel N. Saridakis

We present a novel cosmological framework that unifies matter creation dynamics with thermodynamic principles. Starting with a single-component fluid characterized by a constant equation of state parameter, $\omega$, we introduce a…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-27 Víctor H. Cárdenas , Samuel Lepe

We investigate the cosmological implications of a new class of modified gravity, where the field equations generically include higher-order derivatives of the matter fields, arising from the introduction of non-dynamical auxiliary fields in…

General Relativity and Quantum Cosmology · Physics 2016-07-01 Tiberiu Harko , Francisco S. N. Lobo , Emmanuel N. Saridakis

We examine the second law of thermodynamics in the context of horizon cosmology, in particular, whether the change of total entropy (i.e. the sum of the entropy for the apparent horizon and the entropy for the matter fields) proves to be…

General Relativity and Quantum Cosmology · Physics 2024-04-09 Sergei D. Odintsov , Tanmoy Paul , Soumitra SenGupta

Motivated by the exciting features and a recent proposed general form of the function of non-metricity scalar Q, we investigate the cosmological implications in $f(Q)$ gravity, through the resulting effective dark energy sector, extracting…

General Relativity and Quantum Cosmology · Physics 2022-11-15 Andreas Lymperis

We have investigated the thermodynamical properties of the Universe with dark energy. Adopting the usual assumption in deriving the constant co-moving entropy density that the physical volume and the temperature are independent, we observed…

General Relativity and Quantum Cosmology · Physics 2010-10-27 Yungui Gong , Bin Wang , Anzhong Wang

Non-extensive statistics, namely Tsallis statistics, is applied on a case of a supercritical string cosmology and interesting cosmological modifications are obtained. The two main results we focus on in this work are: fractal scaling for…

High Energy Physics - Theory · Physics 2009-08-07 Ariadne Vergou

We phenomenologically derive a cosmological model that includes both a cosmological constant term $\Lambda/3$ and a dissipative driving term $\beta (2 H^{2} + \dot{H})$ by applying both the first law of thermodynamics and an effective…

General Relativity and Quantum Cosmology · Physics 2026-03-30 Nobuyoshi Komatsu

We consider a cosmological horizon, named thermo-horizon, to which are associated a temperature and an entropy of Bekenstein-Hawking and which obeys the first law for an energy flow calculated through the corresponding limit surface. We…

High Energy Physics - Theory · Physics 2008-11-26 Cécile Barbachoux , Jérome Gariel , Gérard Le Denmat

We investigate the cosmological behavior in a universe governed by time asymmetric extensions of general relativity, which is a novel modified gravity based on the addition of new, time-asymmetric, terms on the Hamiltonian framework, in a…

General Relativity and Quantum Cosmology · Physics 2015-11-11 Genly Leon , Emmanuel N. Saridakis

In this work, we study the evolution of a fractal universe composed of Tsallis holographic dark energy (THDE) and a pressureless dark matter that interact with each other through a mutual interaction. We then reconstruct the interaction…

General Relativity and Quantum Cosmology · Physics 2020-10-28 Abdulla Al Mamon

We formulate power-law holographic dark energy, which is a modified holographic dark energy model based on the extended entropy relation arising from the consideration of state mixing between the ground and the excited ones in the…

General Relativity and Quantum Cosmology · Physics 2022-05-25 Eirini C. Telali , Emmanuel N. Saridakis

We construct gravitational modifications that go beyond Horndeski, namely theories with extended nonminimal derivative couplings, in which the coefficient functions depend not only on the scalar field but also on its kinetic energy. Such…

General Relativity and Quantum Cosmology · Physics 2017-03-01 Tiberiu Harko , Francisco S. N. Lobo , Emmanuel N. Saridakis , Minas Tsoukalas

We propose a relativistic model of dark matter reproducing at once the concordance cosmological model $\Lambda$-Cold-Dark-Matter ($\Lambda$-CDM) at cosmological scales, and the phenomenology of the modified Newtonian dynamics (MOND) at…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-17 Laura Bernard , Luc Blanchet

We have investigated the thermodynamical properties of dark energy. Assuming that the dark energy temperature $T\sim a^{-n}$ and considering that the volume of the Universe enveloped by the apparent horizon relates to the temperature, we…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Yungui Gong , Bin Wang , Anzhong Wang

Coasting cosmology offers an intriguing and straightforward framework for understanding the universe. In this work, we employ the Trans-Planckian Censorship Criterion (TCC) conjecture to test the viability of the coasting cosmology and…

Cosmology and Nongalactic Astrophysics · Physics 2025-09-19 Yunliang Ren , Xiaofeng Yang , Xuwei Zhang , Shuangnan Chen , Yangjun Shi , Cheng Cheng , Xiaolong He , Hoernisa Iminniyaz