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The energy conditions are derived in the context of $f(R,T)$ gravity, where $R$ is the Ricci scalar and $T$ is the trace of the energy-momentum tensor, which can reduce to the well-known conditions in $f(R)$ gravity and general relativity.…

广义相对论与量子宇宙学 · 物理学 2015-06-11 Muhammad Sharif , Muhammad Zubair

The Palatini $f(R,T)$ gravity theory is considered. The standard Einstein-Hilbert action is replaced by an arbitrary function of the Ricci scalar $R$ and of the trace $T$ of the energy-momentum tensor. In the Palatini approach, the Ricci…

广义相对论与量子宇宙学 · 物理学 2021-02-24 J. S. Gonçalves , A. F. Santos

In this paper, $f(R,\lm, T)$ gravity is considered. It is a generalization of the theories $f(R,T)$ and $f(R, \lm)$. This modified theory of gravity exhibits strong geometry-matter coupling. The problem of causality and its violation is…

广义相对论与量子宇宙学 · 物理学 2024-11-19 J. S. Gonçalves , A. F. Santos

We developed the cosmological linear theory of perturbations for $f(Q,T)$ gravity, which is an extension of symmetric teleparallel gravity, with $Q$ the non-metricity and $T$ the trace of the stress-energy tensor. By considering an ansatz…

广义相对论与量子宇宙学 · 物理学 2022-03-11 Antonio Nájera , Amanda Fajardo

Recently a Lagrangian formulation for Rastall Gravity (RG) has been proposed in the framework of f(R, T) gravity. In the present work we obtain Lagrangian formulation for the standard Rastall theory assuming the matter content is a perfect…

广义相对论与量子宇宙学 · 物理学 2020-03-05 Hamid Shabani , Amir Hadi Ziaie

It is known that in f(R) theories of gravity with an independent connection which can be both non-metric and non symmetric, this connection can always be algebraically eliminated in favour of the metric and the matter fields, so long as it…

广义相对论与量子宇宙学 · 物理学 2010-11-03 Vincenzo Vitagliano , Thomas P. Sotiriou , Stefano Liberati

We argue that the recent result of da Rocha and Rodrigues that in two dimensional spacetime the Lagrangian of tetrad gravity is an exact differential [1], despite the claim of the authors, neither proves the Jackiw conjecture [2], nor…

高能物理 - 理论 · 物理学 2007-05-23 N. Kiriushcheva , S. V. Kuzmin

We propose a novel cosmological framework within the $f(R,T)$ type modified gravity theory, incorporating a non-minimally coupled with the higher order of the Ricci scalar ($R$) as well as the trace of the energy-momentum tensor ($T$).…

广义相对论与量子宇宙学 · 物理学 2024-02-06 Shaily , Akanksha Singh , J. K. Singh , Saibal Ray

We investigate the cosmological applications of $F(T,T_G)$ gravity, which is a novel modified gravitational theory based on the torsion invariant $T$ and the teleparallel equivalent of the Gauss-Bonnet term $T_{G}$. $F(T,T_{G})$ gravity…

广义相对论与量子宇宙学 · 物理学 2014-10-29 Georgios Kofinas , Emmanuel N. Saridakis

This paper studies a generic fourth-order theory of gravity with Lagrangian density $f(R,R_c^2,R_m^2, \mathscr{L}_m)$. By considering explicit $R^2$ dependence and imposing the "coherence condition" $f_{R^2}\!=\!f_{R_m^2}\!=\!…

广义相对论与量子宇宙学 · 物理学 2015-07-14 David Wenjie Tian , Ivan Booth

We show that the well-known problem of frame dependence and violation of local Lorentz invariance in the usual formulation of $f(T)$ gravity is a consequence of neglecting the role of spin connection. We re-formulate $f(T)$ gravity…

广义相对论与量子宇宙学 · 物理学 2016-05-06 Martin Krššák , Emmanuel N. Saridakis

This paper aims to recreate the gravitational baryogenesis epoch in the framework of the $f(R,L_m)$ theory of gravity, where $R$ and $L_m$ are the curvature scalar and the matter Langragian, respectively. In particular, we examine the…

广义相对论与量子宇宙学 · 物理学 2023-04-06 Lakhan V. Jaybhaye , Snehasish Bhattacharjee , P. K. Sahoo

We derive the full set of field equations for the Metric-Affine version of the Myrzakulov gravity model and also extend this family of theories to a broader one. More specifically, we consider theories whose gravitational Lagrangian is…

广义相对论与量子宇宙学 · 物理学 2021-06-10 Damianos Iosifidis , Nurgissa Myrzakulov , Ratbay Myrzakulov

In this paper, we shall consider $f(R)$ gravity and its cosmological implications, when an extra matter term generated by thermal effects is added by hand in the Lagrangian. We formulate the equations of motion of the theory as a dynamical…

广义相对论与量子宇宙学 · 物理学 2020-09-29 V. K. Oikonomou , F. P. Fronimos , N. Th. Chatzarakis

We propose a new model of gravity where the Ricci scalar (R) in Einstein-Hilbert action is replaced by an arbitrary function of R and of the norm of energy-momentum tensor i.e., $f(R,T_{\mu\nu}T^{\mu\nu})$. Field equations are derived in…

广义相对论与量子宇宙学 · 物理学 2014-08-04 N. Katirci , Mehmet Kavuk

In this work, two originally separate adjustments for the Friedmann equations are concurrently considered. Firstly, the fractal structure of the black hole horizon region is imposed by the Barrow entropy. The second adjustment is the…

广义相对论与量子宇宙学 · 物理学 2024-06-13 Tuhina Ghorui , Prabir Rudra , Farook Rahaman

The review is devoted to consideration of possible observational consequences of modified gravity theories, suggested for explanation of the contemporary accelerated expansion of the universe. The major attention is paid to F(R)-models. It…

广义相对论与量子宇宙学 · 物理学 2019-11-11 Elena Arbuzova

In this work, we present a new analysis for $f(R,T)$ gravity by exploring the energy momentum tensor. We demonstrate that $f(R,T)$ gravity with the form $f(R,T)=R+2 \kappa^2 \lambda T-2\Lambda$ is equivalent to Running Vacuum Energy (RVE),…

广义相对论与量子宇宙学 · 物理学 2025-02-26 Ahmed Errahmani , Mounia Magrach , Safae Dahmani , Amine Bouali , Taoufik Ouali

The field equations in $f(R)$ gravity derived from the Palatini variational principle and formulated in the Einstein conformal frame yield a cosmological term which varies with time. Moreover, they break the conservation of the…

广义相对论与量子宇宙学 · 物理学 2007-05-23 Nikodem J. Poplawski

A new class of cosmological models in $f(R, T)$ modified theories of gravity proposed by Harko et al. (2011), where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar $R$ and the trace of the stress-energy tensor…

综合物理 · 物理学 2014-07-15 Nasr Ahmed , Anirudh Pradhan