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A single fluid approximation which treats perturbations in baryons and dark matter as equal has sometimes been used to calculate the growth of linear matter density perturbations in the Universe. We demonstrate that properly accounting for…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-12 Soma De , James B. Dent , Lawrence M. Krauss

Cosmic voids in the large-scale structure of the Universe affect the peculiar motions of objects in their vicinity. Although these motions are difficult to observe directly, the clustering pattern of their surrounding tracers in redshift…

Cosmology and Nongalactic Astrophysics · Physics 2015-12-01 Nico Hamaus , P. M. Sutter , Guilhem Lavaux , Benjamin D. Wandelt

We consider the physical setup of a three-dimensional fluid-structure interaction problem. A viscous compressible gas or liquid interacts with a nonlinear, visco-elastic, three-dimensional bulk solid. The latter is described by a hyperbolic…

Analysis of PDEs · Mathematics 2021-08-09 Dominic Breit , Malte Kampschulte , Sebastian Schwarzacher

We study the evolution of a flat Friedmann-Robertson-Walker Universe, filled with a bulk viscous cosmological fluid, in the presence of time varying ``constants''. The dimensional analysis of the model suggests a proportionality between the…

General Relativity and Quantum Cosmology · Physics 2008-11-26 José Antonio Belinchón , Indrajit Chakrabarty

We generalize the $\Lambda$CDM model by introducing a unified EOS to describe the Universe contents modeled as dark viscous fluid, motivated by the fact that a single constant equation of state (EOS) $p=-p_0$ ($p_0>0$) reproduces the…

Astrophysics · Physics 2008-11-26 Jie Ren , Xin-He Meng

In relativistic cosmology, the formation of nonlinear inhomogeneities can induce non-negligible backreaction on late-time expansion. Among the important consequences for precision cosmology is the potential impact on the linear growth of…

General Relativity and Quantum Cosmology · Physics 2026-04-27 Marco Galoppo , Pierre Mourier

In this paper we study the evolution of a LRS Bianchi I Universe, filled with a bulk viscous cosmological fluid in the presence of time varying constants "but" taking into account the effects of a c-variable into the curvature tensor. We…

General Relativity and Quantum Cosmology · Physics 2009-11-10 J. A. Belinchón

Dipole cosmology is the maximally Copernican generalization of the FLRW paradigm that can incorporate bulk flows in the cosmic fluid. In this paper, we first discuss how multiple fluid components with independent flows can be realized in…

Cosmology and Nongalactic Astrophysics · Physics 2023-07-24 Ehsan Ebrahimian , Chethan Krishnan , Ranjini Mondol , M. M. Sheikh-Jabbari

The dark energy dominated warm dark matter (WDM) model is a promising alternative cosmological scenario. We explore large-scale structure formation in this paradigm. We do this in two different ways: with the halo model approach and with…

Cosmology and Nongalactic Astrophysics · Physics 2015-06-03 Aurel Schneider , Robert E. Smith , Andrea V. Maccio , Ben Moore

This paper investigates regarding cosmological implications of a bulk viscous modified Chaplygin gas (MCG) in (2+1)-dimensional Friedmann-Robertson-Walker spacetime, incorporating both theoretical analysis and observational constraints. We…

General Relativity and Quantum Cosmology · Physics 2025-04-29 Praveen Kumar Dhankar , Aritra Sanyal , Albert Munyeshyaka , Saibal Ray , Behnam Pourhassan

Conformally flat spherically symmetric cosmological models representing a charged perfect fluid as well as a bulk viscous fluid distribution have been obtained. The cosmological constant \Lambda is found positive and is a decreasing…

General Relativity and Quantum Cosmology · Physics 2010-11-19 Anirudh Pradhan , Om Prakash Pandey

Viscous unified dark matter models aim to describe the dark sector of the Universe, as the dark matter fluid itself gives rise to an accelerated expansion due to a negative bulk viscous pressure. However, in most studies, radiation is often…

General Relativity and Quantum Cosmology · Physics 2024-06-19 Guillermo Palma , Gabriel Gomez , Norman Cruz

In the present work, we investigate cosmological perturbations of viscous modified chaplygin gas model. Using 1 + 3 covariant formalism, we define covariant and gauge invariant gradient variables, which after the application of scalar…

General Relativity and Quantum Cosmology · Physics 2024-12-31 Albert Munyeshyaka , Praveen Kumar Dhankar , Joseph Ntahompagaze

We study the interaction between incompressible viscous fluids and multilayered elastic structures in a 3D/2D/3D framework, where a 3D fluid interacts with a 2D thin elastic layer, coupled to a 3D thick elastic solid. The system is driven…

Analysis of PDEs · Mathematics 2025-01-14 Claudiu Mîndrilă , Arnab Roy

A plane-symmetric non-static cosmological model representing a bulk viscous fluid distribution has been obtained which is inhomogeneous and anisotropic and a particular case of which is gravitationally radiative. Without assuming any {\it…

General Relativity and Quantum Cosmology · Physics 2014-11-17 Anirudh Pradhan , Hare Ram Pandey

All evolutional paths for all admissible initial conditions of FRW cosmological models with dissipative dust fluid (described by dark matter, baryonic matter and dark energy) are analyzed using dynamical system approach. With that approach,…

Astrophysics · Physics 2008-11-26 Marek Szydlowski , Orest Hrycyna

In this note we derive a new nonlocal and nonlinear dispersive equations capturing the main dynamics of a circular interface separating a light, viscous fluid rising buoyantly through a heavy, more viscous, miscible fluid at small Reynolds…

Analysis of PDEs · Mathematics 2024-12-24 Rafael Granero-Belinchón

Bianchi I cosmological models consisting of a fluid with both bulk and shear viscosity are studied. It is shown how the dynamical importance of the shear and the fluid density change in the course of evolution. Exact solutions with an…

General Relativity and Quantum Cosmology · Physics 2021-03-15 A. Banerjee , S. B. Duttachoudhury , Abhik Kumar Sanyal

Bianchi type V bulk viscous fluid cosmological models are investigated with dynamic cosmological term $\Lambda(t)$. Using a generation technique (Camci {\it et al.}, 2001), it is shown that the Einstein's field equations are solvable for…

General Relativity and Quantum Cosmology · Physics 2008-11-26 Anirudh Pradhan , Kanti Jotania , Anju Rai

The equations describing a two-component cosmological fluid with linearized density perturbations are investigated in the small wavelength or large $k$ limit. The equations are formulated to include a baryonic component, as well as either a…

Astrophysics · Physics 2009-11-11 R. M. Gailis , N. E. Frankel
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