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A system of interacting Brownian particles subject to short-range repulsive potentials is considered. A continuum description in the form of a nonlinear diffusion equation is derived systematically in the dilute limit using the method of…

Statistical Mechanics · Physics 2017-10-12 Maria Bruna , S. Jonathan Chapman , Martin Robinson

We apply the second-order Israel-Stewart theory of relativistic fluid- and thermodynamics to a physically realistic model of a radiative fluid in a simple anisotropic cosmological background. We investigate the asymptotic future of the…

General Relativity and Quantum Cosmology · Physics 2016-05-10 Dmitry Shogin , Per Amund Amundsen

In a recent paper (Moskalenko et al., 2002), it has been shown that the flux of secondary cosmic ray (CR) antiprotons appears to be contradictory to measurements of secondary to primary nuclei ratios in cosmic rays when calculated in the…

Astrophysics · Physics 2010-05-27 V. S. Ptuskin , I. V. Moskalenko , F. C. Jones , A. W. Strong , S. G. Mashnik

We develop a new formalism to study nonlinear evolution in the growth of large-scale structure, by following the dynamics of gravitational clustering as it builds up in time. This approach is conveniently represented by Feynman diagrams…

Astrophysics · Physics 2009-11-13 M. Crocce , R. Scoccimarro

Suspensions of self-motile, elongated particles are a topic of significant current interest, exemplifying a form of `active matter'. Examples include self-propelling bacteria, algae and sperm, and artificial swimmers. Ericksen's model of a…

We investigate the cosmological applications of fluids having an equation of state which is the analog to the one related to the isotropic deformation of crystalline solids, that is containing logarithmic terms of the energy density,…

General Relativity and Quantum Cosmology · Physics 2018-11-14 S. D. Odintsov , V. K. Oikonomou , A. V. Timoshkin , Emmanuel N. Saridakis , R. Myrzakulov

Cosmological linear perturbation theory predicts that the peculiar velocity $V(x)$ and the matter overdensity $\delta(x)$ at a same point $x$ are statistically independent quantities, as log as the initial density fluctuations are random…

Astrophysics · Physics 2009-10-31 Naoki Seto

We study the transfer of cosmological perturbations through a nonsingular cosmological bounce in a special model in which the parameters of the bounce and the equation of state of matter are chosen such as to allow for an exact calculation…

High Energy Physics - Theory · Physics 2008-07-30 Stephon Alexander , Tirthabir Biswas , Robert H. Brandenberger

The Eulerian cosmological fluid equations are used to study the nonlinear mode coupling of density fluctuations. We evaluate the second-order power spectrum including all four-point contributions. In the weakly nonlinear regime we find that…

Astrophysics · Physics 2009-10-22 Bhuvnesh Jain , Edmund Bertschinger

The cosmological fluid equations describe the early gravitational dynamics of cold dark matter (CDM), exposed to a uniform component of dark energy, the cosmological constant $\Lambda$. Perturbative predictions for the fluid equations…

Cosmology and Nongalactic Astrophysics · Physics 2022-08-26 Cornelius Rampf , Sonja Ornella Schobesberger , Oliver Hahn

The cosmic large-scale structure of our Universe is comprised of baryons and cold dark matter (CDM). Yet it is customary to treat these two components as a combined single-matter fluid with vanishing pressure, which is justified only for…

Cosmology and Nongalactic Astrophysics · Physics 2020-12-04 Cornelius Rampf , Cora Uhlemann , Oliver Hahn

Recently, Bartelmann et al. presented a 'Kinetic Field Theory' (KFT) formalism to tackle the difficulties of large scale structure formation. In this approach, the dynamics of a non-equilibrium ensemble of classical particles are examined…

Cosmology and Nongalactic Astrophysics · Physics 2019-05-20 Daniel Geiss , Robert Lilow , Felix Fabis , Matthias Bartelmann

The coupled quintessence model with disformal couplings is treated here to mimic the $\Lambda$CDM background. Using this approach, the quintessence potential does not have to be specified. The model considers a generic fluid coupled to the…

General Relativity and Quantum Cosmology · Physics 2021-03-16 Avishek Dusoye , Alvaro de la Cruz-Dombriz , Peter Dunsby , Nelson J. Nunes

The cosmological fluid equations are used to study the nonlinear mode coupling of density fluctuations. We find that for realistic cosmological spectra there is a significant contribution to the nonlinear evolution on scales of interest to…

Astrophysics · Physics 2007-05-23 Bhuvnesh Jain , Edmund Bertschinger

Motivated by their potential role as dark matter, we study the cosmological evolution of light scalar and vector fields non-minimally coupled to gravity. Our focus is on a situation where the dominant contribution to the energy density…

High Energy Physics - Phenomenology · Physics 2020-03-04 Gonzalo Alonso Álvarez , Joerg Jaeckel , Thomas Hugle

A survey of linearized cosmological fluid equations with a number of different matter components is made. To begin with, the one-component case is reconsidered to illustrate some important mathematical and physical points rarely discussed…

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

At the time of recombination, baryons and photons decoupled and the sound speed in the baryonic fluid dropped from relativistic to the thermal velocities of the hydrogen atoms. This is less than the relative velocities of baryons and dark…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-17 Dmitriy Tseliakhovich , Christopher Hirata

Excluded-volume effects can play an important role in determining transport properties in diffusion of particles. Here, the diffusion of finite-sized hard-core interacting particles in two or three dimensions is considered systematically…

Analysis of PDEs · Mathematics 2012-01-06 Maria Bruna , S. Jonathan Chapman

We propose a procedure to evaluate the impact of nonlinear couplings on the evolution of massive neutrino streams in the context of large-scale structure growth. Such streams can be described by general nonlinear conservation equations,…

Cosmology and Nongalactic Astrophysics · Physics 2015-09-16 Hélène Dupuy , Francis Bernardeau

According to the separate universe conjecture, spherically symmetric sub-regions in an isotropic universe behave like mini-universes with their own cosmological parameters. This is an excellent approximation in both Newtonian and general…

Cosmology and Nongalactic Astrophysics · Physics 2017-02-14 Gábor Rácz , László Dobos , Róbert Beck , István Szapudi , István Csabai