arXiv subjects

Jingyi Chao

Publications and source records attributed to Jingyi Chao.

21 records · Page 2Linked to original sources

arXiv2011

Conformal symmetry and non-relativistic second order fluid dynamics

We study the constraints imposed by conformal symmetry on the equations of fluid dynamics at second order in gradients of the hydrodynamic variables. At zeroth order conformal symmetry implies a constraint on the equation of state, E=2/3 P, where E is the energy density and P is the pressure. At first order, conformal symmetry implies that the bulk viscosity must vanish. We show that at second order conformal invariance requires that two-derivative terms in the stress tensor must be traceless, and that it determines the relaxation of dissipative stresses to the Navier-Stokes form. We verify these results by solving the Boltzmann equation at second order in the gradient expansion. We find that only a subset of the terms allowed by conformal symmetry appear.

hep-th↗

arXiv2010

Thermal Conductivity and Sound Attenuation in Dilute Atomic Fermi Gases

We compute the thermal conductivity and sound attenuation length of a dilute atomic Fermi gas in the framework of kinetic theory. Above the critical temperature for superfluidity, T_c, the quasi-particles are fermions, whereas below T_c, the dominant excitations are phonons. We calculate the thermal conductivity in both cases. We find that at unitarity the thermal conductivity κin the normal phase scales as κ~ T^{3/2}. In the superfluid phase we find κ~ T^{2}. At high temperature the Prandtl number, the ratio of the momentum and thermal diffusion constants, is 2/3. The ratio increases as the temperature is lowered. As a consequence we expect sound attenuation in the normal phase just above T_c to be dominated by shear viscosity. We comment on the possibility of extracting the shear viscosity of the dilute Fermi gas at unitarity using measurements of the sound absorption length.

cond-mat.quant-gas↗

arXiv2009

Thermal conductivity of color-flavor locked quark matter

We compute the thermal conductivity of color-flavor locked (CFL) quark matter. At temperatures below the scale set by the gap in the quark spectrum, transport properties are determined by collective modes. In this work we focus on the contribution from the lightest modes, the superfluid phonon and the massive neutral kaon. The calculation is done in the framework of kinetic theory, using variational solutions of the linearized Boltzmann equation. We find that the thermal conductivity due to phonons is κ^P =1.04 10^{26} mu_{500}^8 Δ_{50}^{-6} erg/(cm s K), where μ_{500} is the chemical potential in units of 500 MeV and Δ_{50} is the gap in units of 50 MeV. The contribution of kaons is κ^K = 2.81 10^{21} f_{π,100}^4 T_{MeV}^{1/2} m_{10}^{-5/2} erg/(cm s K), where f_{π,100} is the pion decay constant in units of 100 MeV, T_{MeV} is the temperature in units of 1 MeV, and m_{10} is the kaon mass in units of 10 MeV. These values are smaller than previous estimates, but still much larger than (in the case of phonons) or similar to (for kaons) the corresponding values in nuclear matter. From the phonon thermal conductivity we estimate that a CFL quark matter core of a compact star becomes isothermal on a timescale of a few seconds.

hep-ph↗