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This article describes the theory of cosmological perturbations around a homogeneous and anisotropic universe of the Bianchi I type. Starting from a general parameterisation of the perturbed spacetime a la Bardeen, a complete set of gauge…

Astrophysics · Physics 2008-11-26 Thiago S. Pereira , Cyril Pitrou , Jean-Philippe Uzan

We investigate how spontaneous Lorentz symmetry breaking in bumblebee gravity modifies particle dynamics, thermodynamics, and vacuum energy around a static black hole background. Starting from the optical-mechanical correspondence, we…

General Relativity and Quantum Cosmology · Physics 2026-01-13 A. A. Araújo Filho , K. E. L. de Farias , E. Passos , F. A. Brito , Ali Övgün , Hassan Hassanabadi , V. B. Bezerra , Amilcar R. Queiroz

A Kerr-Sen-like black hole solution results from Einstein-bumblebee gravity. It contains a Lorentz violating (LV) parameter that enters when the bumblebee field receives vacuum expectation value through a spontaneously breaking of the…

General Relativity and Quantum Cosmology · Physics 2022-05-25 Sohan Kumar Jha , Anisur Rahaman

The anisotropies induced by Lorentz-violating fields pose significant challenges for the search for compact objects in non-vacuum environments. In this work, we demonstrate that introducing couplings between Lorentz-violating fields and…

General Relativity and Quantum Cosmology · Physics 2025-07-24 Renan B. Magalhães , Leandro A. Lessa , Rodolfo Casana

We extend the standard theory of cosmological perturbations to homogeneous but anisotropic universes. We present an exhaustive computation for the case of a Bianchi I model, with a residual isotropy between two spatial dimensions, which is…

Astrophysics · Physics 2008-11-26 A. E. Gumrukcuoglu , Carlo R. Contaldi , Marco Peloso

The ARCADE 2 collaboration has reported a significant excess in the isotropic radio background, whose homogeneity cannot be reconciled with clustered sources. This suggests a cosmological origin prior to structure formation. We investigate…

Cosmology and Nongalactic Astrophysics · Physics 2013-02-06 James M. Cline , Aaron C. Vincent

Cosmic Microwave Background anomalies suggest that the Universe is slightly anisotropic, so a Cosmological Model that does not satisfy the Cosmological Principle is necessary. Anisotropic Bianchi models have been studied given that they…

General Relativity and Quantum Cosmology · Physics 2017-02-07 Ericsson López , Mario Llerena

In this study, we found a new traversable wormhole solution in the framework of a bumblebee gravity model. With these types of models, the Lorentz symmetry violation arises from the dynamics of a bumblebee vector field that is non-minimally…

General Relativity and Quantum Cosmology · Physics 2019-01-30 Ali Övgün , Kimet Jusufi , İzzet Sakallı

Within the framework of the spontaneous Lorentz symmetry breaking, we consider a metric--affine generalization of the gravitational sector of the Standard--Model Extension (SME), including the Lorentz--violating (LV) coefficients $u$ and…

General Relativity and Quantum Cosmology · Physics 2024-07-03 A. A. Araújo Filho , J. R. Nascimento , A. Yu. Petrov , P. J. Porfírio

The behaviour of the flat anisotropic model of the Universe with a scalar field is explored within the framework of quantum cosmology. The principal moment of the account of an anisotropy is the presence either negative potential barrier or…

General Relativity and Quantum Cosmology · Physics 2015-06-25 V. N. Folomeev , V. Ts. Gurovich

We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived.…

General Relativity and Quantum Cosmology · Physics 2016-02-09 Pavan K. Aluri , Sukanta Panda , Manabendra Sharma , Snigdha Thakur

The detection of a time variation of the angle between two distant sources would reveal an anisotropic expansion of the Universe. We study this effect of "cosmic parallax" within the "ellipsoidal universe" model, namely a particular…

Cosmology and Nongalactic Astrophysics · Physics 2011-06-29 L. Campanelli , P. Cea , G. L. Fogli , L. Tedesco

We investigate non-metricity effects on electron scattering in metric-affine bumblebee gravity, where spontaneous Lorentz symmetry breaking is induced by a vector field acquiring a nonzero vacuum expectation value. Treating the affine…

General Relativity and Quantum Cosmology · Physics 2026-03-18 A. A. Araújo Filho

In this paper, we examine the physical consequences of a recently introduced black hole solution in bumblebee gravity [1]. The geometry is first presented and then reformulated through suitable coordinate adjustments, which make its global…

General Relativity and Quantum Cosmology · Physics 2026-04-02 A. A. Araújo Filho , N. Heidari , Iarley P. Lobo , V. B. Bezerra

We consider a metric-affine extension to the gravitational sector of the Standard-Model Extension for the Lorentz-violating coefficients $u$ and $s^{\mu\nu}$. The general results, which are applied to a specific model called metric--affine…

General Relativity and Quantum Cosmology · Physics 2023-10-18 A. A. Araújo Filho , J. R. Nascimento , A. Yu. Petrov , P. J. Porfírio

In theories where the Lorentz symmetry of gravity is spontaneously broken, a non-minimally coupled bumblebee vector field acquires a nonzero vacuum expectation value, leading to modifications of standard General Relativity (GR). In this…

General Relativity and Quantum Cosmology · Physics 2026-03-11 Faizuddin Ahmed , Shubham Kala , Ahmad Al-Badawi

In this paper, we investigate the properties of relativistic stars made of isotropic matter within the framework of the minimal Standard Model Extension, where a Bumblebee field (BF) coupled to spacetime induces spontaneous Lorentz symmetry…

General Relativity and Quantum Cosmology · Physics 2025-05-15 Grigoris Panotopoulos , Ali Övgün

In this work, the interior spacetime of stars is built in a Lorentz symmetry breaking model called bumblebee gravity. Firstly, we calculated the modified Tolman-Oppenheimer-Volkoff equation in this context of modified gravity. Then we show…

General Relativity and Quantum Cosmology · Physics 2025-02-13 Juliano C. S. Neves , Fernando G. Gardim

In this work, the behavior, evolution, and expansion of the universe are investigated within a Lorentz-violating framework driven by Tsallis holographic dark energy. The cosmological extension is implemented through a spontaneously…

General Relativity and Quantum Cosmology · Physics 2026-02-03 E. M. Siquieri , D. S. Cabral , A. F. Santos

In this work, we calculate the quasi-normal frequencies from a bumblebee traversable wormhole. The bumblebee wormhole model is based on the bumblebee gravity, which exhibits a spontaneous Lorentz symmetry breaking. Supporting by the Lorentz…

General Relativity and Quantum Cosmology · Physics 2019-05-22 R. Oliveira , D. M. Dantas , Victor Santos , C. A. S. Almeida