scholarly journals Lattice study of transport coefficients in second order dissipative hydrodynamics

2011 ◽  
Author(s):  
Y. Kohno ◽  
Masayuki Asakawa ◽  
Masakiyo Kitazawa ◽  
Chiho Nonaka
Keyword(s):  
Transport Coefficients ◽  
Second Order

scholarly journals Cosmic ray momentum diffusion in the presence of nonlinear Alfvén waves

1996 ◽  
Vol 3 (1) ◽  
pp. 66-76 ◽  
Author(s):  
G. Michałek ◽  
M. Ostrowsky
Keyword(s):  
Diffusion Coefficient ◽  
Shock Waves ◽  
Wave Field ◽  
Transport Coefficients ◽  
Cosmic Ray ◽  
High Amplitude ◽  
Second Order ◽  
Fermi Acceleration ◽  
Large Wave ◽  
Wave Fields

Abstract. The relation between the spatial diffusion coefficient along the magnetic field, kII, and the momentum diffusion coefficient, Dp, for relativistic cosmic ray particles is modelled using Monte Carlo simulations. Wave fields with vanishing wave helicity and cross-helicity, constructed by superposing 'Alfvén-like' waves are considered. As the result, particle trajectories in high amplitude wave fields and then - by averaging over these trajectories - the values of transport coefficients are derived. The modelling is performed at various wave amplitudes, from δ B/B0 = 0.15 to 2.0, and for a number of wave field types. At our small amplitudes approximately the quasi-linear theory (QLT) estimates for kII and Dp are reproduced. However, with growing wave amplitude the simulated results show a small divergence from the QLT ones, with kII decreasing slower than theoretical prediction and the opposite being true for Dp. The wave field form gives only a slight influence on the wave-particle interactions at large wave amplitudes δ B/B0 ~ 1. The parameter characterizing the relative efficiency of the second-order to the first-order acceleration at shock waves, Dp κII is given in the QLT approximation by the Skilling formula V2A p2 / 9. In simulations together with increasing δ B it increases above this scale in all the cases under our study. Consequences of the present results for the second-order Fermi acceleration at shock waves are briefly addressed.

scholarly journals Relativistic non-resistive viscous magnetohydrodynamics from the kinetic theory: a relaxation time approach

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Ankit Kumar Panda ◽  
Ashutosh Dash ◽  
Rajesh Biswas ◽  
Victor Roy
Keyword(s):  
Magnetic Field ◽  
Relaxation Time ◽  
Transport Coefficients ◽  
Second Order ◽  
Navier Stokes ◽  
Relaxation Time Approximation ◽  
Moment Approximation ◽  
System Of Particles ◽  
Anisotropic Transport ◽  
The Magnetic Field

Abstract We derive the relativistic non-resistive, viscous second-order magnetohydrodynamic equations for the dissipative quantities using the relaxation time approximation. The Boltzmann equation is solved for a system of particles and antiparticles using Chapman-Enskog like gradient expansion of the single-particle distribution function truncated at second order. In the first order, the transport coefficients are independent of the magnetic field. In the second-order, new transport coefficients that couple magnetic field and the dissipative quantities appear which are different from those obtained in the 14-moment approximation [1] in the presence of a magnetic field. However, in the limit of the weak magnetic field, the form of these equations are identical to the 14-moment approximation albeit with different values of these coefficients. We also derive the anisotropic transport coefficients in the Navier-Stokes limit.

scholarly journals Ricci cosmology in light of astronomical data

2021 ◽  
Vol 81 (10) ◽  
Author(s):  
Roberto Caroli ◽  
Mariusz P. Da̧browski ◽  
Vincenzo Salzano
Keyword(s):  
Transport Coefficients ◽  
Second Law Of Thermodynamics ◽  
Momentum Tensor ◽  
Second Order ◽  
Main Concern ◽  
Equilibrium Pressure ◽  
Spacetime Curvature ◽  
Cosmological Data ◽  
Standard Set ◽  
The Universe

AbstractRecently, a new cosmological framework, dubbed Ricci cosmology, has been proposed. Such a framework has emerged from the study of relativistic dynamics of fluids out of equilibrium in a curved background and is characterised by the presence of deviations from the equilibrium pressure in the energy–momentum tensor which are due to linear terms in the Ricci scalar and the Ricci tensor. The coefficients in front of such terms are called the second order transport coefficients and they parametrise the fluid response to the pressure terms arising from the spacetime curvature. Under the preliminary assumption that the second order transport coefficients are constant, we find the simplest solution of Ricci cosmology in which the presence of pressure terms causes a departure from the perfect fluid redshift scaling for matter components filling the Universe. In order to test the viability of this solution, we make four different ansätze on the transport coefficients, giving rise to four different cases of our model. On the physical ground of the second law of thermodynamics for fluids with non-equilibrium pressure, we find some theoretical bounds (priors) on the parameters of the models. Our main concern is then the check of each of the case against the standard set of cosmological data in order to obtain the observational bounds on the second order transport coefficients. We find those bounds also realising that Ricci cosmology model is compatible with $$\Lambda $$ Λ CDM cosmology for all the ansätze.

Sign in / Sign up

Export Citation Format

Share Document