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Diffusion in an evolving environment is studied by continuos-time Monte Carlo simulations. Diffusion is modelled by continuos-time random walkers on a lattice, in a dynamic environment provided by bubbles between two one-dimensional…

Soft Condensed Matter · Physics 2010-11-22 Janne Juntunen , Juha Merikoski

We study spatially homogeneous and isotropic solutions to the equations of motion derived from dilaton gravity, in the presence of a special combination of higher derivative terms in the gravitational action. All solutions are nonsingular.…

General Relativity and Quantum Cosmology · Physics 2009-10-31 R. Brandenberger , Richard Easther , J. Maia

A multicomponent extension of our recent theory of simple fluids [ U.M.B. Marconi and S. Melchionna, Journal of Chemical Physics, 131, 014105 (2009) ] is proposed to describe miscible and immiscible liquid mixtures under inhomogeneous, non…

Statistical Mechanics · Physics 2011-02-11 Umberto Marini Bettolo Marconi , Simone Melchionna

We study the dynamics of a spherically symmetric thin shell of perfect fluid embedded in d-dimensional Anti-de Sitter space-time. In global coordinates, besides collapsing solutions, oscillating solutions are found where the shell bounces…

General Relativity and Quantum Cosmology · Physics 2015-07-07 Javier Mas , Alexandre Serantes

In this manuscript, we investigate the oscillatory behaviour of the anisotropy in the diagonal Bianchi-I spacetimes. Our starting point is a simplification of Einstein's equations using only observable or physical variables. As a…

General Relativity and Quantum Cosmology · Physics 2021-04-02 Leandro G Gomes , Bruno B. Bizarria , Gabriel A. de Souza Silva , William O. Clavijo

We present a numerical method to deal efficiently with large numbers of particles in incompressible fluids. The interactions between particles and fluid are taken into account by a physically motivated ansatz based on locally defined drag…

Condensed Matter · Physics 2016-08-31 W. Kalthoff , S. Schwarzer , G. H. Ristow , H. J. Herrmann

We study the evolution of a flat Friedmann-Robertson- Walker Universe, filled with a bulk viscous cosmological fluid, in the presence of variable gravitational and cosmological constants. The dimensional analysis of the model suggest a…

General Relativity and Quantum Cosmology · Physics 2009-09-25 J. A. Belinchon , T. Harko , M. K. Mak

Exact particle-like static, spherically and/or cylindrically symmetric solutions to the equations of interacting scalar and electromagnetic field system have been obtained. We considered Freedman-Robertson-Walker (FRW) space-time as an…

General Relativity and Quantum Cosmology · Physics 2019-04-22 B. Saha

We consider a thermodynamically consistent diffuse interface model describing two-phase flows of incompressible fluids in a non-isothermal setting. This model was recently introduced in a previous paper of ours, where we proved existence of…

Analysis of PDEs · Mathematics 2014-06-09 Michela Eleuteri , Elisabetta Rocca , Giulio Schimperna

A model for an expanding noncommutative acoustic fluid analogous to a Friedmann-Robertson-Walker geometry is derived. For this purpose, a noncommutative Abelian Higgs model is considered in a (3+1)-dimensional spacetime. In this scenario,…

High Energy Physics - Theory · Physics 2021-06-30 M. A. Anacleto , C. H. G. Bessa , F. A. Brito , E. J. B. Ferreira , E. Passos

We study the dynamics near finite-time singularities of flat isotropic universes filled with two interacting but otherwise arbitrary perfect fluids. The overall dynamical picture reveals a variety of asymptotic solutions valid locally…

General Relativity and Quantum Cosmology · Physics 2015-06-04 Spiros Cotsakis , Georgia Kittou

We analyze a diffuse interface model for multi-phase flows of $N$ incompressible, viscous Newtonian fluids with different densities. In the case of a bounded and sufficiently smooth domain existence of weak solutions in two and three space…

Analysis of PDEs · Mathematics 2024-01-15 Helmut Abels , Harald Garcke , Andrea Poiatti

We consider density fluctuations of a two-fluid model consisting of hydrogen plasma and radiation prior to the cosmic hydrogen recombination. As investigation method that of the dispersion relations is applied, which have been derived from…

Astrophysics · Physics 2009-11-07 Eva Gessner , Heinz Dehnen

We consider the dynamics of thin two-dimensional viscous droplets on chemically heterogeneous surfaces moving under the combined effects of slip, mass transfer and capillarity. The resulting long-wave evolution equation for the droplet…

Fluid Dynamics · Physics 2021-12-20 Danny Groves , Nikos Savva

Methods of dynamical systems have been used to study homogeneous and isotropic cosmological models with a varying speed of light (VSL). We propose two methods of reduction of dynamics to the form of planar Hamiltonian dynamical systems for…

General Relativity and Quantum Cosmology · Physics 2008-07-22 Marek Szydlowski , Adam Krawiec

We numerically evolve spherically symmetric solutions to the linear wave equation on some expanding Friedmann-Lema\^itre-Robertson-Walker (FLRW) spacetimes and study the respective asymptotics for large times. We find a quantitative…

General Relativity and Quantum Cosmology · Physics 2026-02-17 Flavio Rossetti , Alex Vañó-Viñuales

Motion of an ultra-relativistic perfect fluid in space-time with the Kasner metrics is investigated by the Hamiltonian method. It is found that in the limit of small times a tendency takes place to formation of strong inhomogeneities in…

General Relativity and Quantum Cosmology · Physics 2014-11-17 V. P. Ruban , D. I. Podolsky

We investigate the cosmic dynamics of Rastall gravity in non-flat Friedmann-Robertson-Walker (FRW) space-time with barotropic fluid. In this context, we are concerned about the class of model satisfying the affine equation of state. We…

General Relativity and Quantum Cosmology · Physics 2022-07-27 Ashutosh Singh , Gyan Prakash Singh , Anirudh Pradhan

We analyze the properties of a generic cosmological fluid described by the van der Waals equation of state. Exact solutions for the energy density evolution are found as implicit functions of the scale factor for a flat…

General Relativity and Quantum Cosmology · Physics 2016-02-11 Rudinei C. S. Jantsch , Marcus H. B. Christmann , Gilberto M. Kremer

For the model of a compressible barotropic fluid on a two dimensional rotating Riemmanian manifold we discuss a special class of smooth solutions having a form of a steady non-singular vortex moving with a bearing field. The model can be…

Mathematical Physics · Physics 2012-01-24 Olga S. Rozanova , Jui-Ling Yu , Chin-Kun Hu