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Tensor-scalar theories of gravitation are commonly employed as extensions of General Relativity that allow to describe a much wider phenomenology. They are also naturally generated as low energy limit of higher-dimensional or unified…

General Physics · Physics 2025-12-09 F. Minotti , G. Modanese

We generalize the notion of constant-roll inflation earlier introduced in General Relativity (GR) and $f(R)$ gravity to inflationary models in more general scalar-tensor gravity. A number of novel exact analytic solutions for a FLRW…

General Relativity and Quantum Cosmology · Physics 2020-02-25 Hayato Motohashi , Alexei A. Starobinsky

We review thermodynamic properties of modified gravity theories such as $F(R)$ gravity and $f(T)$ gravity, where $R$ is the scalar curvature and $T$ is the torsion scalar in teleparallelism. In particular, we explore the equivalence between…

General Relativity and Quantum Cosmology · Physics 2016-06-22 Kazuharu Bamba

The classical evolution and the quantum generation processes of the scalar- and tensor-type cosmological perturbations in the context of a broad class of generalized gravity theories are presented in unified forms. The exact forms of final…

Astrophysics · Physics 2014-10-13 H. Noh , J. Hwang

We extend the thermodynamic derivation of gravity in the Jacobson framework by generalizing the Clausius relation through a nontrivial entropy functional. We show that entropy deformations appear as modifications of the effective…

General Relativity and Quantum Cosmology · Physics 2026-04-14 H. R. Fazlollahi

Based on the conventional metric tensor and driven by a nearly constant energy density, cosmic inflation, characterized by a remarkably accelerated expansion, was proposed as an early epoch in the Universe. The energy density is typically…

General Relativity and Quantum Cosmology · Physics 2026-05-05 Swapnil K. Singh , Saleh O. Allehabi , Azzah A. Alshehri , Mahmoud Nasar , Abdel Nasser Tawfik

We propose a topological model of induced gravity (pregeometry) where both Newton's coupling constant and the cosmological constant appear as integration constants in solving field equations. The matter sector of a scalar field is also…

General Relativity and Quantum Cosmology · Physics 2017-02-15 Ichiro Oda

Gravity theory is the basis of modern cosmological models. Thirring-Feynman's tensor field approach to gravitation is an alternative to General Relativity (GR). Though Field Gravity (FG) approach is still developing subject, it opens new…

General Relativity and Quantum Cosmology · Physics 2016-08-31 Yurij Baryshev

In this paper, we investigate a class of Horndeski scalar-tensor theory of gravity for warm inflation. We present some models where the early-time acceleration is realized in the weak and in the strong dissipation regime. Cosmological…

General Relativity and Quantum Cosmology · Physics 2017-07-13 L. Sebastiani , S. Myrzakul , R. Myrzakulov

We search for viable f(R) theories of gravity, making use of the equivalence between such theories and scalar-tensor gravity. We find that models can be made consistent with solar system constraints either by giving the scalar a high mass…

Astrophysics · Physics 2008-11-26 Thomas Faulkner , Max Tegmark , Emory F. Bunn , Yi Mao

Tensor models are more-index generalizations of the so-called matrix models, and provide models of quantum gravity with the idea that spaces and general relativity are emergent phenomena. In this paper, a renormalization procedure for the…

High Energy Physics - Theory · Physics 2015-03-17 Naoki Sasakura

We propose that the mass-temperature relation of galaxy clusters is a prime candidate for testing gravity theories beyond Einstein's general relativity, for modified gravity models with universal coupling between matter and the scalar…

Cosmology and Nongalactic Astrophysics · Physics 2017-02-15 Amir Hammami , David F. Mota

In this work, the $f(\mathcal{G},T)$ theory of gravity is recast in terms of the $\phi$ and $\psi$ fields within the scalar-tensor formulation, where $\mathcal{G}$ is the Gauss-Bonnet term and $T$ denotes the trace of the energy-momentum…

General Relativity and Quantum Cosmology · Physics 2023-12-20 Adam Z. Kaczmarek , Dominik Szczęśniak

We propose the study of constant-roll inflation in $F(R)$ gravity. We use two different approaches, one that relates an $F(R)$ gravity to well known scalar models of constant-roll and a second that examines directly the constant-roll…

General Relativity and Quantum Cosmology · Physics 2017-12-06 S. Nojiri , S. D. Odintsov , V. K. Oikonomou

We consider a modified gravity framework for inflation by adding to the Einstein-Hilbert action a direct $f(\phi)T$ term, where $\phi$ is identified as the inflaton and $T$ is the trace of the energy-momentum tensor. The framework goes to…

General Relativity and Quantum Cosmology · Physics 2022-02-23 Xinyi Zhang , Che-Yu Chen , Yakefu Reyimuaji

A scalar theory of gravity extending Newtonian gravity to include field energy as its source is developed. The physical implications of the theory are probed through its spherically symmetric (source) solutions. The aim is to demonstrate…

General Relativity and Quantum Cosmology · Physics 2015-06-22 Joel Franklin

A theory of gravity with torsion is examined in which the torsion tensor is constructed from the exterior derivative of an antisymmetric rank two potential plus the dual of the gradient of a scalar field. Field equations for the theory are…

General Relativity and Quantum Cosmology · Physics 2009-11-07 Charro Gruver , Richard Hammond , P. F. Kelly

Within the context of scalar-tensor gravity, we explore the generalized second law (GSL) of gravitational thermodynamics. We extend the action of ordinary scalar-tensor gravity theory to the case in which there is a non-minimal coupling…

General Relativity and Quantum Cosmology · Physics 2014-05-27 A. Abdolmaleki , T. Najafi , K. Karami

Attractor solutions that give dynamical reasons for dark energy to act like the cosmological constant, or behavior close to it, are interesting possibilities to explain cosmic acceleration. Coupling the scalar field to matter or to gravity…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-17 Jorge L. Cervantes-Cota , Roland de Putter , Eric V. Linder

Inspired by Verlinde's idea, some modified versions of entropic gravity have appeared in the literature. Extending them in a unified formalism, we derive the generalized gravitational equations accordingly. From gravitational equations, the…

High Energy Physics - Theory · Physics 2012-11-27 Tower Wang