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We introduce the notion of topological fragility and briefly discuss some examples from the literature. An important example of this type of fragility is the way globally anisotropic Bianchi V generalisations of the FLRW $k=-1$ model result…

General Relativity and Quantum Cosmology · Physics 2015-06-25 M. J. Reboucas , R. K. Tavakol , A. F. F. Teixeira

The Cosmological Principle, which states that the Universe is homogeneous and isotropic (when averaged on large scales), is the foundational assumption of Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmologies such as the current standard…

Cosmology and Nongalactic Astrophysics · Physics 2025-12-15 Nathan Secrest , Sebastian von Hausegger , Mohamed Rameez , Roya Mohayaee , Subir Sarkar

Anisotropic inflation is an interesting model with an U(1) gauge field and it predicts the statistical anisotropy of the curvature perturbation characterized by a parameter $g_*$. However, we find that the background gauge field does not…

Cosmology and Nongalactic Astrophysics · Physics 2018-02-14 Tomohiro Fujita , Ippei Obata

Anisotropic cosmological models are constructed in $f(R,T)$ gravity theory to investigate the dynamics of universe concerning the late time cosmic acceleration. Using a more general and simple approach, the effect of the coupling constant…

General Physics · Physics 2018-10-05 B. Mishra , Sankarsan Tarai , S. K. Tripathy

In this article, we review some aspects of gravitational field and cosmology based on Finsler and Finsler-like generalized metric structures. The geometrical framework of these spaces allows further investigation of locally-anisotropic…

General Relativity and Quantum Cosmology · Physics 2025-05-15 P. C. Stavrinos , A. Triantafyllopoulos

We study inflationary universes with an SU(3) gauge field coupled to an inflaton through a gauge kinetic function. Although the SU(3) gauge field grows at the initial stage of inflation due to the interaction with the inflaton, nonlinear…

High Energy Physics - Theory · Physics 2021-11-25 Pengyuan Gao , Kazufumi Takahashi , Asuka Ito , Jiro Soda

In this work we investigate the anisotropic conformal structure of the gravitational field incorporating dark gravity in a generalized Lagrange geometric framework on the Lorentz tangent bundle and we present two applications; the…

General Relativity and Quantum Cosmology · Physics 2023-08-28 Christos Savvopoulos , Panayiotis Stavrinos

Scalar field cosmologies with a generalized harmonic potential and a matter fluid with a barotropic Equation of State (EoS) with barotropic index $\gamma$ for the Locally Rotationally Symmetric (LRS) Bianchi I and flat…

General Relativity and Quantum Cosmology · Physics 2021-06-03 Genly Leon , Sebastián Cuéllar , Esteban González , Samuel Lepe , Claudio Michea , Alfredo D. Millano

Most existing cosmological entanglement studies are focused on the isotropic Robertson-Walker (RW) spacetime. Here we go beyond this limitation and study the influence of anisotropy on entanglement generated by dynamical spacetime. Since…

General Relativity and Quantum Cosmology · Physics 2017-11-16 Roberto Pierini , Shahpoor Moradi , Stefano Mancini

We investigate cosmologies where the accelerated expansion of the Universe is driven by a field with an anisotropic equation of state. We model such scenarios within the Bianchi I framework, introducing two skewness parameters to quantify…

Astrophysics · Physics 2009-06-23 Tomi Koivisto , David F. Mota

In this work we investigate a model for the early Universe in a Bianchi type-I metric, where the sources of the gravitational field are a fermionic and a bosonic field, interacting through a Yukawa potential, following the standard model of…

General Relativity and Quantum Cosmology · Physics 2016-02-23 M. O. Ribas , L. L. Samojeden , F. P. Devecchi , G. M. Kremer

A powerful result in theoretical cosmology states that a subset of anisotropic Bianchi models can be seen as the homogeneous limit of (standard) linear cosmological perturbations. Such models are precisely those leading to Friedmann…

General Relativity and Quantum Cosmology · Physics 2025-06-03 Thiago S. Pereira , Cyril Pitrou

The presence of a nonconformally invariant term in the photon sector of the Lorentz-violating extension of Standard Model of particle physics, the "Kosteleck\'{y} term" $\mathcal{L}_K \propto (k_F)_{\alpha \beta \mu \nu} F^{\alpha \beta}…

Cosmology and Nongalactic Astrophysics · Physics 2009-11-06 Leonardo Campanelli

We formulate cosmological perturbation theory around the spatially curved FLRW background in the context of metric-affine gauge theory of gravity which includes torsion and nonmetricity. Performing scalar-vector-tensor decomposition of the…

General Relativity and Quantum Cosmology · Physics 2024-07-18 Katsuki Aoki , Sebastian Bahamonde , Jorge Gigante Valcarcel , Mohammad Ali Gorji

In this paper, we have investigated the density perturbations and cosmological evolution in the FLRW universe in presence of a cosmic magnetic field, which may be assumed to mimic primordial magnetic fields. Such magnetic fields have…

High Energy Physics - Theory · Physics 2025-08-11 Samarjit Chakraborty , Sarbari Guha

Based on Cohen \& Glashow's very special relativity [A. G. Cohen and S. L. Glashow, Phys. Rev. Lett. {\bf 97} (2006) 021601], we propose an anisotropic modification to the Friedmann-Robertson-Walker (FRW) line element. An arbitrarily…

Cosmology and Nongalactic Astrophysics · Physics 2013-06-10 Zhe Chang , Ming-Hua Li , Xin Li , Sai Wang

We study the anisotropic Bianchi type-I cosmological model at late times, taking into account quantum gravitational corrections in the formalism of the exact renormalization group flow of the effective average action for gravity. The…

General Relativity and Quantum Cosmology · Physics 2020-02-24 Rituparna Mandal , Sunandan Gangopadhyay , Amitabha Lahiri

Cosmological solitons are widely predicted by scenarios of the early Universe. In this work, we investigate the isotropic background and anisotropies of gravitational waves (GWs) induced by soliton isocurvature perturbations, especially…

Cosmology and Nongalactic Astrophysics · Physics 2025-04-04 Di Luo , Yan-Heng Yu , Jun-Peng Li , Sai Wang

We study the solution of the gravitational field equations in $AdSL_{4}$-gauged gravity, a gauge-theoretic extension of general relativity based on the $AdSL_{4}$ algebra. In this formulation, the antisymmetric gauge field $B^{ab}$,…

High Energy Physics - Theory · Physics 2026-03-04 Oktay Cebecioğlu , Salih Kibaroğlu

We consider the non-minimal model of gravity in $Y(R) F^2$-form. We investigate a particular case of the model, for which the higher order derivatives are eliminated but the scalar curvature $R$ is kept to be dynamical via the constraint…

General Relativity and Quantum Cosmology · Physics 2017-11-17 Muzaffer Adak , Ozgur Akarsu , Tekin Dereli , Ozcan Sert