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The research work in the thesis is focused on the thermodynamic analysis of cosmological models, especially the models that explain late-time cosmic acceleration. According to the cosmological principle, the universe is spatially…

General Relativity and Quantum Cosmology · Physics 2024-06-05 Tanima Duary

In this paper, we find several teleparallel $F(T,B)$ solutions for a Robertson--Walker (TRW) cosmological spacetime. We first set and solve the $F(T,B)$-type field equations for a linear perfect fluid. Using similar techniques, we then find…

General Relativity and Quantum Cosmology · Physics 2025-01-22 Fateme Gholami , Alexandre Landry

In this paper, we consider the Bianchi type-I space-time with perfect fluid as matter content of the Universe in the framework of $f(Q)$ gravity (where $% Q$ is the non-metricity scalar) recently proposed by Jim\'{e}nez et al. (Phys. Rev. D…

General Relativity and Quantum Cosmology · Physics 2022-08-18 M. Koussour , S. H. Shekh , M. Bennai

Late time cosmic acceleration may be achieved by modifying gravity on large scales. This should also have consequences on the evolution of perturbations. We thus extend our study of exponential infrared $f(T)$ teleparallel gravity to…

Cosmology and Nongalactic Astrophysics · Physics 2023-01-11 Mahmoud Hashim , Amr A. El-Zant , Waleed El Hanafy , Alexey Golovnev

We investigate the impact of conformal transformations on the physical properties of solution trajectories in nonmetricity gravity. Specifically, we explore the phase-space and reconstruct the cosmological history of a spatially flat…

General Relativity and Quantum Cosmology · Physics 2023-12-19 Nikolaos Dimakis , Kevin Duffy , Alex Giacomini , Alexander Yu. Kamenshchik , Genly Leon , Andronikos Paliathanasis

We demonstrate that the high isotropy of the Cosmic Microwave Background (CMB), combined with the Copernican principle, is not sufficient to prove homogeneity of the universe -- in contrast to previous results on this subject. The crucial…

General Relativity and Quantum Cosmology · Physics 2009-10-31 Chris Clarkson , Richard Barrett

We calculate deviations in cosmological observables as a function of parameters in a class of connection-based models of quantum gravity. In this theory non-trivial modifications to the background cosmology can occur due to a distortion of…

Cosmology and Nongalactic Astrophysics · Physics 2023-02-01 Michael W. Toomey , Savvas Koushiappas , Bruno Alexandre , João Magueijo

We consider the most general teleparallel theory of gravity whose action is a linear combination of the five scalar invariants which are quadratic in the torsion tensor. Since two of these invariants possess odd parity, they naturally allow…

General Relativity and Quantum Cosmology · Physics 2021-05-11 Manuel Hohmann , Christian Pfeifer

We study the consequences due to time varying $G$ and $\Lambda$ in scalar-tensor theories of gravity for cosmology, inspired by the modifications introduced by the Renormalization Group (RG) equations in the Quantum Einstein Gravity. We…

Astrophysics · Physics 2009-11-10 Claudio Rubano , Paolo Scudellaro

We investigate the quantum modified cosmological dynamical equations in a Friedmann-Robertson-Walker universe filled with a barotropic fluid and a general non-canonical scalar field characterized by a Lagrangian similar to k-essence model…

General Relativity and Quantum Cosmology · Physics 2024-03-06 Rituparna Mandal , Soma Sanyal

We present the geometric foundations and derivations of equations of motion for symmetric teleparallel theories of gravity in the coincident gauge and covariant frameworks. We discuss the theoretical challenges introduced by the auxiliary…

General Relativity and Quantum Cosmology · Physics 2024-02-27 Daniel Blixt , Alexey Golovnev , Maria-Jose Guzman , Ramazan Maksyutov

Given the remarkable success of the $\Lambda$CDM model in fitting various cosmological observations, a pertinent question in assessing the phenomenological viability of modified gravity theories is whether they can reproduce an exactly…

General Relativity and Quantum Cosmology · Physics 2025-04-30 Saikat Chakraborty , Jibitesh Dutta , Daniele Gregoris , Khamphee Karwan , Wompherdeiki Khyllep

In this paper, we consider a gravitational action containing a combination of the Ricci scalar, $R$, and the topological Gauss--Bonnet term, $G$. Specifically, we study the cosmological features of a particular class of modified gravity…

General Relativity and Quantum Cosmology · Physics 2023-03-15 Francesco Bajardi , Rocco D'Agostino

This paper investigates the cosmological implications of the modified gravity framework known as $f(R,\Sigma, T)$ gravity, focusing on its potential to unify and extend current cosmological models. The theory, introduced by Bakry and…

General Relativity and Quantum Cosmology · Physics 2025-03-04 N. Myrzakulov , S. H. Shekh , Anirudh Pradhan

We consider the Brans-Dicke theory in non-metricity gravity, which belongs to the family of symmetric teleparallel scalar-tensor theories. Our focus lies in exploring the implications of the conformal transformation, as we derive the…

General Relativity and Quantum Cosmology · Physics 2023-10-26 Andronikos Paliathanasis

In this article, we investigate scalar field cosmology in the coincident $f(Q)$ gravity formalism. We calculate the motion equations of $f(Q)$ gravity under the flat Friedmann-Lema\^{i}tre-Robertson-Walker background in the presence of a…

General Relativity and Quantum Cosmology · Physics 2024-04-12 Sayantan Ghosh , Raja Solanki , P. K. Sahoo

This work investigates alternative theories of gravity, the solutions to their field equations and the constraints that can be imposed upon them from observation and experiment. Specifically, we consider the cosmologies and spherically…

General Relativity and Quantum Cosmology · Physics 2007-05-23 T. Clifton

In this paper, we present an accelerating cosmological model by constraining the free parameters using the cosmological datasets in an extended symmetric teleparallel gravity for the flat and anisotropic space-time. We employ a time…

General Relativity and Quantum Cosmology · Physics 2023-06-27 S. A. Narawade , M. Koussour , B. Mishra

The {\it{Cosmological Boundary Flux Parameter}} is a novel proposal that attempts to explain the origin of the cosmological parameter $\Lambda$ purely by geometric nature. Then we implement this new approach to a flat FLRW universe along…

General Relativity and Quantum Cosmology · Physics 2022-12-29 Rafael Hernández-Jiménez , Claudia Moreno , Mauricio Bellini , C. Ortiz

Bianchi I cosmological solutions in f(T) gravity are discussed. We start from diagonal metrics and tetrads and show that their dynamical equations are pretty much tractable analytically, with a possible arena for physical applications. Then…

General Relativity and Quantum Cosmology · Physics 2026-02-24 Alexey Golovnev , Mustafa M. Hemida