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In this note we comment on remarks about our recent effort to understand the specificities of the Boltzmann equation in the context of the alternative theories of gravity with non-minimal coupling between curvature and matter.

General Relativity and Quantum Cosmology · Physics 2020-05-11 Orfeu Bertolami , Cláudio Gomes

A certain class of exact solutions of Einstein Maxwell spacetime in general relativity is discussed which demonstrates at the level of theory that, when certain parametric resonance condition is met, the interaction of electromagnetic field…

General Relativity and Quantum Cosmology · Physics 2023-10-24 Ruodi Yan , Yun Kau Lau

The variational field equations of Brans-Dicke scalar-tensor theory of gravitation are given in a non-Riemannian setting in the language of exterior differential forms over 4-dimensional spacetimes. A conformally re-scaled Robinson-Trautman…

General Relativity and Quantum Cosmology · Physics 2019-02-15 Muzaffer Adak , Tekin Dereli , Yorgo Senikoglu

The careful analysis of the duality properties of Riemann's curvature tensor points to possibility of extension of Einstein's General Relativity to the nonabelian Yang-Mills theory. The motion equations of the theory are Yang-Mills'…

General Relativity and Quantum Cosmology · Physics 2007-05-23 A. L. Koshkarov

Semiclassical approximation to the Wheeler-DeWitt equation which corresponds to gravity with a minimally coupled scalar field has been performed. To the leading order, vacuum Einstein's equation along with the functional Schrodinger…

General Relativity and Quantum Cosmology · Physics 2017-07-26 Abhik Kumar Sanyal

We show that, in four-dimensional spacetimes with an arbitrary Einstein metric, with and without a cosmological constant, perturbative dynamical degrees of freedom in generic quadratic-curvature gravity can be decoupled into massless and…

General Relativity and Quantum Cosmology · Physics 2019-07-01 Yuki Niiyama , Yuya Nakamura , Ryosuke Zaimokuya , Yu Furuya , Yuuiti Sendouda

We present locally scale (Weyl) covariant generalisation of Minimal Massive Gravity theory using the language of exterior differential forms on Riemann-Cartan-Weyl space-times. The theory is expressed by a locally scale invariant action and…

General Relativity and Quantum Cosmology · Physics 2019-04-26 Tekin Dereli , Cem Yetişmişoğlu

We extend our previous Schwarzschild metric-based studies of gravitational--electromagnetic (GEM) coupling to rotating black holes by working directly in a curvature-based Newman--Penrose/Teukolsky framework on Kerr spacetime. Within a…

General Relativity and Quantum Cosmology · Physics 2025-11-26 Fawzi Aly , Dejan Stojkovic

In this work, we examine a family of $pp$-wave solutions of Minimal Massive 3d Gravity (MMG) minimally coupled with the Maxwell-Chern-Simons theory. An elaborate investigation of the field equations shows that the theory admits $pp$-wave…

High Energy Physics - Theory · Physics 2022-08-02 Hakan Cebeci , Tekin Dereli , Seçil Şentorun

Here, we report pp waves configurations of three-dimensional gravity for which a scalar field nonminimally coupled to them acts as a source. In absence of self-interaction the solutions are gravitational plane waves with a profile fixed in…

High Energy Physics - Theory · Physics 2016-08-16 Eloy Ayón-Beato , Mokhtar Hassaïne

The coupling of gravity to a scalar field raises a number of interesting questions of principle since the usual minimal coupling obtained by replacing ordinary derivatives with covariant derivatives is not available -- they are the same…

General Relativity and Quantum Cosmology · Physics 2011-10-26 Y. N. Srivastava , J. Swain , A. Widom

Emergent modified gravity is a post-Einsteinian gravitational theory where spacetime geometry is not fundamental but rather emerges from the gravitational degrees of freedom in a non-trivial way. The specific relationship between geometry…

General Relativity and Quantum Cosmology · Physics 2024-12-23 Martin Bojowald , Erick I. Duque , S. Shankaranarayanan

We review cosmology in non-minimal Yang-Mills/Maxwell theory, in which the Yang-Mills/electromagnetic field couples to a function of the scalar curvature. We show that power-law inflation can be realized due to the non-minimal gravitational…

High Energy Physics - Theory · Physics 2008-11-09 Kazuharu Bamba , Shin'ichi Nojiri

In this work we aim to revive the interest for non-minimal derivative coupling theories of gravity, in light of the GW170817 event. These theories include a string motivated non-minimal kinetic term for the scalar field of the form $\sim…

General Relativity and Quantum Cosmology · Physics 2024-02-06 V. K. Oikonomou

Theories with a non-minimal coupling between the space-time curvature and matter fields introduce an extra force due to the non-conservation of the matter energy momentum. In the present work the theoretical consistency of such couplings is…

General Relativity and Quantum Cosmology · Physics 2013-10-02 Nicola Tamanini , Tomi S. Koivisto

We consider a non-minimally coupled curvature-matter gravity model (NMC) with a Weyl connection, a theory referred to as non-minimally coupled Weyl connection gravity (NMCWCG). The Weyl connection is an affine connection that is not…

General Relativity and Quantum Cosmology · Physics 2020-03-30 Rodrigo Baptista , Orfeu Bertolami

Free massive higher spin fields in weak background gravitational fields are discussed. Contrary to the spin one case, higher spin fields should have nontrivial non-minimal couplings to the curvature. A precise analysis is given for the spin…

High Energy Physics - Theory · Physics 2016-07-01 Masafumi Fukuma , Hikaru Kawai , Katsuta Sakai , Junji Yamamoto

In a recent paper [1], it was introduced a new class of gravitational theories with two local degrees of freedom. The existence of these theories apparently challenges the distinctive role of general relativity as the unique non-linear…

General Relativity and Quantum Cosmology · Physics 2018-10-30 Raúl Carballo-Rubio , Francesco Di Filippo , Stefano Liberati

We examine an extension of General Relativity with an explicit non-minimal coupling between matter and curvature. The purpose of this work is to present an overview of the implications of the latter to various contexts, ranging from…

General Relativity and Quantum Cosmology · Physics 2014-01-20 Orfeu Bertolami , Jorge Páramos

In a previous paper on coupled gravitational and electromagnetic perturbations of Reissner-Nordstr\"om spacetime in a polarized setting, we derived a system of wave equations for two independent quantities, one related to the Weyl curvature…

General Relativity and Quantum Cosmology · Physics 2018-04-18 Elena Giorgi