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The universe is smooth on large scales but very inhomogeneous on small scales. Why is the spacetime on large scales modeled to a good approximation by the Friedmann equations? Are we sure that small-scale non-linearities do not induce a…

Cosmology and Nongalactic Astrophysics · Physics 2015-05-18 Daniel Baumann , Alberto Nicolis , Leonardo Senatore , Matias Zaldarriaga

In this paper, we consider numerical approximations of a binary fluid-surfactant phase-field model coupled with the fluid flow, in which the system is highly nonlinear that couples the incompressible Navier-Stokes equations and two…

Numerical Analysis · Mathematics 2018-04-13 Xiaofeng Yang

We present a description of cosmic neutrinos as a dispersive fluid. In this approach, the neutrino phase space is reduced to density and velocity fields alongside a scale-dependent sound speed. This sound speed depends on redshift, the…

Cosmology and Nongalactic Astrophysics · Physics 2017-04-05 Derek Inman , Ue-Li Pen

Significant improvements in the computational performance of the lattice-Boltzmann (LB) model, coded in FORTRAN90, were achieved through application of enhancement techniques. Applied techniques include optimization of array memory layouts,…

Computational Physics · Physics 2020-06-24 Hakan Başağaoğlu , John R. Harwell , Hoa Nguyen , Sauro Succi

Modifications on the predictions about the matter power spectrum based on the hypothesis of a tiny contribution from a degenerate Fermi gas (DFG) test-fluid to some dominant cosmological scenario are investigated. Reporting about the…

Cosmology and Nongalactic Astrophysics · Physics 2015-03-19 E. L. D. Perico , Alex E. Bernardini

The main effect of massive neutrinos on the large-scale structure consists in a few percent suppression of matter perturbations on all scales below their free-streaming scale. Such effect is of particular importance as it allows to…

Cosmology and Nongalactic Astrophysics · Physics 2018-03-13 Rossana Ruggeri , Emanuele Castorina , Carmelita Carbone , Emiliano Sefusatti

We focus here on a class of fourth-order parabolic equations that can be written as a system of second-order equations by introducing an auxiliary variable. We design a novel second-order fully discrete mixed finite element method to…

Numerical Analysis · Mathematics 2020-08-28 Sana Keita , Abdelaziz Beljadid , Yves Bourgault

Active matter, encompassing natural systems, converts surrounding energy to sustain autonomous motion, exhibiting unique non-equilibrium behaviors such as active turbulence and phase separation. In this study, we develop a continuum…

Soft Condensed Matter · Physics 2026-05-06 Sohail Ahmed , Zixiang Lin , Zijie Qu

We initiate a systematic study of the perturbative nonlinear dynamics of cosmological fluctuations in dark sectors comprising a fraction of non-cold dark matter, for example ultra-light axions or light thermal relics. These mixed dark…

Cosmology and Nongalactic Astrophysics · Physics 2026-02-02 Francesco Verdiani , Emanuele Castorina , Ennio Salvioni , Emiliano Sefusatti

We show that the relativistic effects are negligibly small in the non-linear density and velocity bispectra. Although the non-linearities of Einstein equation introduce additional non-linear terms to the Newtonian fluid equations, the…

Cosmology and Nongalactic Astrophysics · Physics 2014-05-28 Sang Gyu Biern , Jinn-Ouk Gong , Donghui Jeong

Nonlinear perturbation of Fuchsian systems are studied in a region including two singularities. It is proved that such systems are generally not analytically equivalent to their linear part (they are not linearizable) and the obstructions…

Classical Analysis and ODEs · Mathematics 2009-11-13 Rodica D. Costin

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

Our current understanding of the Universe depends on the interplay of several distinct "matter" components, which interact mainly through gravity, and electromagnetic radiation. The nature of the different components, and possible…

General Relativity and Quantum Cosmology · Physics 2012-08-28 G. L. Comer , Patrick Peter , N. Andersson

This paper provides a framework to strong time periodic solutions of quasilinear evolution equations. The novelty of this approach is that zero is allowed to be a spectral value of the underlying linearized operator. This approach is then…

Analysis of PDEs · Mathematics 2023-11-02 Felix Brandt , Matthias Hieber , Arnab Roy

We study the counter terms in the Eulerian version of the EFT of Large Scale Structure. We reformulate the equations to solve for the displacement of fluid elements as a bookkeeping variable and study the structure of the counter terms in…

Cosmology and Nongalactic Astrophysics · Physics 2015-11-06 Matias Zaldarriaga , Mehrdad Mirbabayi

Using methods of kinetic theory and liquid state theory we propose a description of the non-equilibrium behavior of molecular fluids which takes into account their microscopic structure and thermodynamic properties. The present work…

Statistical Mechanics · Physics 2009-02-24 Umberto Marini Bettolo Marconi , Simone Melchionna

We introduce a neural-network-assisted Boltzmann framework that learns the binary-collision map of microswimmers directly from data and uses it to evaluate collision integrals efficiently. Using a representative model swimmer, the learned…

Soft Condensed Matter · Physics 2025-10-29 Haruki Hayano , Akira Furukawa , Kang Kim

Bifurcation theory and continuation methods are well-established tools for the analysis of nonlinear mechanical systems subject to periodic forcing. We illustrate the added value and the complementary information provided by singularity…

Classical Physics · Physics 2017-03-08 G. I. Cirillo , G. Habib , G. Kerschen , R. Sepulchre

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 an ad hoc extension of the Lattice-Boltzmann method that allows the simulation of non-Newtonian fluids described by generalized Newtonian models. We extensively test the accuracy of the method for the case of shear-thinning and…

Soft Condensed Matter · Physics 2015-06-25 Susana Gabbanelli , German Drazer , Joel Koplik