62,444 research outputs found
A Review of Time Relaxation Methods
The time relaxation model has proven to be effective in regularization of Navier–Stokes Equations. This article reviews several published works discussing the development and implementations of time relaxation and time relaxation models (TRMs), and how such techniques are used to improve the accuracy and stability of fluid flow problems with higher Reynolds numbers. Several analyses and computational settings of TRMs are surveyed, along with parameter sensitivity studies and hybrid implementations of time relaxation operators with different regularization techniques
Decoherence rates for Galilean covariant dynamics
We introduce a measure of decoherence for a class of density operators. For
Gaussian density operators in dimension one it coincides with an index used by
Morikawa (1990). Spatial decoherence rates are derived for three large classes
of the Galilean covariant quantum semigroups introduced by Holevo. We also
characterize the relaxation to a Gaussian state for these dynamics and give a
theorem for the convergence of the Wigner function to the probability
distribution of the classical analog of the process.Comment: 23 page
Relaxation time of non-conformal plasma
We study effective relaxation time of viscous hydrodynamics of strongly
coupled non-conformal gauge theory plasma using gauge theory/string theory
correspondence. We compute leading corrections to the conformal plasma
relaxation time from the relevant deformations due to dim-2 and dim-3
operators. We discuss in details the relaxation time tau_eff of N=2^* plasma.
For a certain choice of masses this theory undergoes a phase transition with
divergent specific heat c_V ~ |1-T_c/T|^(-1/2). Although the bulk viscosity
remains finite all the way to the critical temperature, we find that tau_eff
diverges near the critical point as tau_eff ~ |1-T_c/T|^(-1/2).Comment: 11 pages, 1 figure; v2: references adde
Optical and dc conductivities of cuprates: Spin-fluctuation scattering in the t-J model
A microscopic theory of the electrical conductivity within
the t-J model is developed. An exact representation for is
obtained using the memory-function technique for the relaxation function in
terms of the Hubbard operators, and the generalized Drude law is derived. The
relaxation rate due to the decay of charge excitations into particle-hole pairs
assisted by antiferromagnetic spin fluctuations is calculated in the
mode-coupling approximation. Using results for the spectral function of spin
excitations calculated previously, the relaxation rate and the optical and dc
conductivities are calculated in a broad region of doping and temperatures. The
reasonable agreement of the theory with experimental data for cuprates proves
the important role of spin-fluctuation scattering in the charge dynamics.Comment: 13 pages,15 figures, v.2, publication referenc
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