相对论流体粘性输运系数的场论计算和动力学计算的一致性

Second order relativistic viscous hydrodynamics within an effective description of hot QCD medium

The second-order hydrodynamic equations for evolution of shear and bulk viscous pressure have been derived within the framework of covariant kinetic theory based on the effective fugacity quasiparticle model. The temperature-dependent fugacity parameter in the equilibrium distribution function leads to a mean field term in the Boltzmann equation which affects the interactions in the hot QCD matter. The viscous corrections to distribution function, up to second-order in gradient expansion, have been obtained by employing a Chapman-Enskog like iterative solution of the effective Boltzmann equati…

Dissipative Spin Dynamics in Relativistic Matter

Using classical description of spin degrees of freedom, we extend recent formulation of the perfect-fluid hydrodynamics for spin-polarized fluids to the case including dissipation. Our work is based on the analysis of classical kinetic equations for massive particles with spin-1/2, with the collision terms treated in the relaxation time approximation. The kinetic-theory framework determines the structure of viscous and diffusive terms and allows to explicitly calculate a complete set of new kinetic coefficients that characterize dissipative spin dynamics.

Non-equilibrium Chiral Magnetic/Vortical Effects in Viscous Fluids

We utilize the chiral kinetic theory in a relaxation-time approximation to investigate the nonlinear anomalous responses of chiral fluids with viscous effects. Unlike the cases in equilibrium, it is found that the chiral magnetic effect and chiral vortical effect are modified by the shear and bulk strengths. Particularly, the shear strength could result in charged Hall currents for chiral magnetic and chiral vortical effects, which propagate perpendicular to applied magnetic fields and vorticity. These quantum corrections stemming from side jumps and anomalies are dissipative and pertinent to …

相对论三阶耗散流体动力学的动力学理论

Relativistic third-order dissipative fluid dynamics from kinetic theory

本文从动力学理论出发，导出了一个新的三阶流体力学剪应力张量演化方程。采用Chapman-Enskog展开式迭代求解碰撞项为弛豫时间近似的Boltzmann方程，得到非平衡相空间分布函数。随后，推导出了剪应力张量的演化方程，从其动力学定义到三阶梯度。我们量化的意义，新的推导在一维标度展开，并表明，使用三阶粘性方程得到的结果在这里推导的Boltzmann方程的弛豫时间近似的精确解提供了一个很好的近似。我们还表明，使用我们的方程得到的压力各向异性的时间演化是在更好的协议与运输结果相比，现有的三阶计算的基础上的热力学第二定律。

Causality and existence of solutions of relativistic viscous fluid dynamics with gravity

A new approach is described to help improve the foundations of relativistic viscous fluid dynamics and its coupling to general relativity. Focusing on neutral conformal fluids constructed solely in terms of hydrodynamic variables, we derive the most general viscous energy-momentum tensor yielding equations of motion of second order in the derivatives, which is shown to provide a novel type of generalization of the relativistic Navier-Stokes equations for which causality holds. We show how this energy-momentum tensor may be derived from conformal kinetic theory. We rigorously prove existence, u…

Nonlinear causality of general first-order relativistic viscous hydrodynamics

Effective theory arguments are used to derive the most general energy-momentum tensor of a relativistic viscous fluid with an arbitrary equation of state (in the absence of other conserved currents) that is first-order in the derivatives of the energy density and flow velocity and does not include extended variables such as in Mueller-Israel-Stewart-like theories. This energy-momentum tensor leads to a causal theory, provided one abandons the usual conventions for the out-of-equilibrium hydrodynamic variables put forward by Landau-Lifshitz and Eckart. In particular, causality requires nonzero …

Observational constraints and some toy models in $f(Q)$ gravity with bulk viscous fluid

The standard formulation of general relativity fails to describe some recent interests in the universe. It impels us to go beyond the standard formulation of gravity. The $f(Q)$ gravity theory is an interesting modified theory of gravity, where the gravitational interaction is driven by the nonmetricity $Q$. This study aims to examine the cosmological models with the presence of bulk viscosity effect in the cosmological fluid within the framework of $f(Q)$ gravity. We construct three bulk viscous fluid models, i.e. (i) for the first model, we assuming the Lagrangian $f(Q)$ as linear dependence…