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We consider some classes of Horndeski theories in four dimensions for which a certain combination of the Einstein equations within a spherical ansatz splits into two distinct branches. Recently, for these theories, some integrability and…

High Energy Physics - Theory · Physics 2023-09-26 Mokhtar Hassaine , Ulises Hernandez-Vera , Franco Lara-Munoz

In this paper we, first, generalize the quasilocal definition of the stress energy tensor of Einstein gravity to the case of Lovelock gravity, by introducing the tensorial form of surface terms that make the action well-defined. We also…

High Energy Physics - Theory · Physics 2009-11-11 M. H. Dehghani , N. Bostani , A. Sheykhi

We construct the most general, to cubic order in curvature, theory of gravity whose (most general) static spherically symmetric vacuum solutions are fully described by a single field equation. The theory possess the following remarkable…

High Energy Physics - Theory · Physics 2017-06-07 Robie A. Hennigar , David Kubiznak , Robert B. Mann

Thermodynamic interpretations of gravity often arise from applying the Clausius relation to spacetime horizons. In modified gravity theories with higher-order equations of motion, such as f(R) and scalar-tensor gravity, this relation…

General Relativity and Quantum Cosmology · Physics 2026-04-07 Vishnu A Pai , Vishnu S Namboothiri , Titus K Mathew

We explore the thermodynamic analysis at the apparent horizon in the framework of Rastall theory of gravity. We take different entropies such as the Bakenstein, logarithmic corrected, power law corrected, and the Renyi entropies. We…

General Physics · Physics 2018-12-04 Kazuharu Bamba , Abdul Jawad , Salman Rafique , Hooman Moradpour

A general formalism for understanding the thermodynamics of horizons in spherically symmetric spacetimes is developed. The formalism reproduces known results in the case of black hole spacetimes. But its power lies in being able to handle…

General Relativity and Quantum Cosmology · Physics 2010-11-19 T. Padmanabhan

We analyze black hole thermodynamics in a generalized theory of gravity whose Lagrangian is an arbitrary function of the metric, the Ricci tensor and a scalar field. We can convert the theory into the Einstein frame via a "Legendre"…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Jun-ichirou Koga , Kei-ichi Maeda

We explore thermodynamics of the apparent horizon in $f(T)$ gravity with both equilibrium and non-equilibrium descriptions. We find the same dual equilibrium/non-equilibrium formulation for $f(T)$ as for $f(R)$ gravity. In particular, we…

General Relativity and Quantum Cosmology · Physics 2015-05-30 Kazuharu Bamba , Chao-Qiang Geng

In this paper, we first generalize the formulation of entropic gravity to (n+1)-dimensional spacetime. Then, we propose an entropic origin for Gauss-Bonnet gravity and more general Lovelock gravity in arbitrary dimensions. As a result, we…

General Physics · Physics 2013-04-16 A. Sheykhi , H. Moradpour , N. Riazi

Applying Clausius relation with energy-supply defined by the unified first law of thermodynamics formalism to the apparent horizon of a massive cosmological model proposed lately, the corrected entropic formula of the apparent horizon is…

General Relativity and Quantum Cosmology · Physics 2013-04-19 Hui Li , Yi Zhang

We study P-V criticality of black holes in Lovelock gravities in the context of horizon thermodynamics. The corresponding first law of horizon thermodynamics emerges as one of the Einstein-Lovelock equations and assumes the universal…

General Relativity and Quantum Cosmology · Physics 2017-02-01 Devin Hansen , David Kubiznak , Robert B. Mann

This paper explores the non-equilibrium behavior of thermodynamics at the apparent horizon of isotropic and homogeneous universe model in $f(\mathcal{G},T)$ gravity ($\mathcal{G}$ and $T$ represent the Gauss-Bonnet invariant and trace of…

General Relativity and Quantum Cosmology · Physics 2018-03-13 M. Sharif , Ayesha Ikram

Using the generalized procedure proposed by \emph{Wu et al}\cite{wu} recently, we construct the first law of thermodynamics on apparent horizon in a general braneworld model with curvature correction terms on the brane and in the bulk,…

General Relativity and Quantum Cosmology · Physics 2010-01-07 Tao Zhu , Ji-Rong Ren , Shu-Fan Mo

The motive of this work is to study gravitational collapse in Vaidya space-time embedded in Galileon gravity theory. Galileon gravity is in fact an infrared modification of Einstein gravity, which was proposed as a generalization of the 4D…

General Physics · Physics 2015-06-18 Prabir Rudra , Ujjal Debnath

With the help of a masslike function which has dimension of energy and equals to the Misner-Sharp mass at the apparent horizon, we show that the first law of thermodynamics of the apparent horizon $dE=T_AdS_A$ can be derived from the…

High Energy Physics - Theory · Physics 2008-11-26 Yungui Gong , Anzhong Wang

Black hole thermodynamics in Lorentz-violating gravity is subtle because different excitations propagate at different speeds and hence identify different causal horizons. We revisit Einstein--AEther gravity using the covariant phase space…

General Relativity and Quantum Cosmology · Physics 2026-04-01 Walter Arata , Stefano Liberati , Giulio Neri

For Rindler observers accelerating close to the horizon in local patches around a spacetime point, the matter-energy passing through the horizon increases the entropy and heat energy. Jacobson has showed that the Einstein equation can be…

General Relativity and Quantum Cosmology · Physics 2014-01-29 Swastik Bhattacharya

Spacetimes with horizons show a resemblance to thermodynamic systems and one can associate the notions of temperature and entropy with them. In the case of Einstein-Hilbert gravity, it is possible to interpret Einstein's equations as the…

High Energy Physics - Theory · Physics 2008-11-26 Aseem Paranjape , Sudipta Sarkar , T. Padmanabhan

We propose a modified gravity theory by extending the Einstein-Hilbert action with an arbitrary function of the Ricci scalar and the Kretschmann scalar invariants. The resulting modified Friedmann equations for a spatially flat FRW universe…

General Relativity and Quantum Cosmology · Physics 2026-05-29 A. Dehyadegari , A. Sheykhi

In this paper, we investigate the thermodynamic aspects of quadratic gravity in a $D$-dimensional Friedmann-Lemaitre-Robertson-Walker (FLRW) universe. First, we derive the field equations and the effective energy-momentum tensor for…

General Relativity and Quantum Cosmology · Physics 2025-07-17 Navid Safarzadeh Ilkhchi , Amin Rezaei Akbarieh , Yaghoub Heydarzade