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I deduce an exact and analytic Bianchi type I solution of Einsteins field equations, which generalizes the isotropic LambdaCDM universe model to a corresponding model with anisotropic expansion. The main point of the article is to present…

General Relativity and Quantum Cosmology · Physics 2024-06-17 Øyvind G. Grøn

In this paper, we have derived the field equations in an extended theory of gravity in an anisotropic space time background and in the presence of magnetic field. The physical and geometrical parameters of the models are determined with…

General Relativity and Quantum Cosmology · Physics 2022-07-19 Sankarsan Tarai , Fakhereh Md. Esmaeili , B. Mishra , S. K. Tripathy

Understanding the observations of dynamical tracers and the trajectories of lensed photons at galactic scales within the context of General Relativity (GR), requires the introduction of a hypothetical dark matter dominant component. The…

Astrophysics of Galaxies · Physics 2018-11-28 X. Hernandez , R. A. Sussman , L. Nasser

The expansion history of the Universe reconstructed from a combination of recent data indicates a preference for a changing Dark Energy (DE) density. Moreover, the DE density appears to be increasing with cosmic time, with its equation of…

Cosmology and Nongalactic Astrophysics · Physics 2020-02-19 Alex Zucca , Levon Pogosian , Alessandra Silvestri , Yuting Wang , Gong-Bo Zhao

We introduce a new logotropic model based on a complex scalar field with a logarithmic potential that unifies dark matter and dark energy. The scalar field satisfies a nonlinear wave equation generalizing the Klein-Gordon equation in the…

General Relativity and Quantum Cosmology · Physics 2022-10-05 Pierre-Henri Chavanis

We study Gravitational Waves (GWs) in the context of Massive Gravity, an extension to General Relativity (GR) where the fluctuations of the metric have a nonzero mass, and specifically investigate the effect of the tensor modes on the…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-13 Dennis Bessada , Oswaldo D. Miranda

We investigate a phenomenological extension of the standard $\Lambda$CDM framework, the $\Omega_1\Omega_2$-$\Lambda$CDM model, in which the total energy density of the universe is expanded in powers of $1+z$. This parameterization recovers…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-20 Suresh Kumar

We constrain deviations from general relativity (GR) including both redshift and scale dependencies in the modified gravity (MG) parameters. In particular, we employ the under-used binning approach and compare the results to functional…

Cosmology and Nongalactic Astrophysics · Physics 2022-04-18 Cristhian Garcia-Quintero , Mustapha Ishak , Orion Ning

We extend the idea of mimetic gravity to a Randall-Sundrum II braneworld model. As for the 4-dimensional mimetic gravity, we isolate the conformal degree of freedom of 5-dimensional gravity in a covariant manner. We assume the bulk metric…

General Relativity and Quantum Cosmology · Physics 2017-05-09 Naser Sadeghnezhad , Kourosh Nozari

We derive new constraints on the $E_G$ statistic as a test of gravity, combining the CMB lensing map estimated from Data Release 6 (DR6) of the Atacama Cosmology Telescope with SDSS BOSS CMASS and LOWZ galaxy data. We develop an analysis…

In this letter, we report the observational constraints on a Bianchi type I anisotropic extension of $w$CDM model with spatial curvature from observational data including Baryon Acoustic Oscillations (BAO), Cosmic chronometers (CC), Big…

Cosmology and Nongalactic Astrophysics · Physics 2024-05-21 Vikrant Yadav , Rajpal , Pardeep , Manish Yadav , Santosh Kumar Yadav

In this paper, we consider a normal branch of the DGP cosmological model with a quintessence scalar field on the brane as the dark energy component. Using the dynamical system approach, we study the stability properties of the model. We…

General Relativity and Quantum Cosmology · Physics 2021-02-24 Arvin Ravanpak , Golnaz Farpour Fadakar

Anisotropic spherically symmetric solutions within the framework of the Brans-Dicke theory are uncovered through a unique gravitational decoupling approach involving a minimal geometric transformation. This transformation effectively…

General Relativity and Quantum Cosmology · Physics 2023-11-01 Kazuharu Bamba , M. Z. Bhatti , Z. Yousaf , Z. Shoukat

Anisotropy effects on the finite-size critical behavior of a two-dimensional Ising model on a general triangular lattice in an infinite-strip geometry with periodic, antiperiodic, and free boundary conditions (bc) in the finite direction…

Statistical Mechanics · Physics 2012-10-05 Boris Kastening

The nature of dark matter is increasingly constrained by cosmological data. In this paper, we examine the implications of the Cosmic Microwave Background anisotropy limits on the density of cold dark matter under different theoretical…

Astrophysics · Physics 2009-11-07 A. Melchiorri , J. Silk

In our study, we explored the properties of a spatially homogeneous and anisotropic Bianchi type V I0 Universe. Our investigation centered on integrating cosmic domain walls into the f(R, T) theory of gravitation, initially proposed by…

General Relativity and Quantum Cosmology · Physics 2024-03-05 V. R. Patil , J. L. Pawde , R. V. Mapari , S. K. Waghmare

We investigate a two-parameter extension of the $\Lambda_{\rm s}$CDM model by allowing variations in the effective number of neutrino species $N_{\rm eff}$ and their total mass $\sum m_\nu$. Our motivation is twofold: (i) to examine whether…

Cosmology and Nongalactic Astrophysics · Physics 2025-01-14 Anita Yadav , Suresh Kumar , Cihad Kibris , Ozgur Akarsu

Bimetric gravity is an interesting alternative to standard GR given its potential to provide a concrete theoretical framework for a ghost-free massive gravity theory. Here we investigate a class of Bimetric gravity models for their…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-12 Ajay Bassi , Shahnawaz A. Adil , Manvendra Pratap Rajvanshi , Anjan A. Sen

Cosmic strings, topological defects predicted by high-energy theories, may contribute to the late-time expansion of the Universe, effectively mimicking dynamical dark energy. We investigate four phenomenological extensions of the…

Cosmology and Nongalactic Astrophysics · Physics 2026-04-06 Hanyu Cheng , Eleonora Di Valentino , Luca Visinelli

The Brans-Dicke (BD) theory of gravity is taken as a possible theory of k-essence coupled to gravity. It then has been realized that the BD scalar field does indeed play a role of a k-essence, but in a very unique way which distinguishes it…

Astrophysics · Physics 2007-05-23 Hongsu Kim
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