@article{braby_chao_schaefer_2011, title={Viscosity spectral functions of the dilute Fermi gas in kinetic theory}, volume={13}, ISSN={["1367-2630"]}, url={http://inspirehep.net/record/878937}, DOI={10.1088/1367-2630/13/3/035014}, abstractNote={We compute the viscosity spectral function of the dilute Fermi gas for different values of the s-wave scattering length a, including the unitarity limit a→∞. We perform the calculation in kinetic theory by studying the response to a non-trivial background metric. We find the expected structure consisting of a diffusive peak in the transverse shear channel and a sound peak in the longitudinal channel. At zero momentum the width of the diffusive peak is ω0≃(2ε)/(3η) where ε is the energy density and η is the shear viscosity. At finite momentum the spectral function approaches the collisionless limit and the width is of the order of ω0∼k(T/m)1/2.}, journal={NEW JOURNAL OF PHYSICS}, author={Braby, Matt and Chao, Jingyi and Schaefer, Thomas}, year={2011}, month={Mar} }
@article{alford_braby_mahmoodifar_2010, title={Shear viscosity from kaon condensation in color-flavor-locked quark matter}, volume={81}, ISSN={["1089-490X"]}, DOI={10.1103/physrevc.81.025202}, abstractNote={We calculate the kaonic contribution to the shear viscosity of quark matter in the kaon-condensed color-flavor-locked phase (CFL-K0). This contribution comes from a light pseudo-Goldstone boson that arises from the spontaneous breaking of the flavor symmetry by the kaon condensate. The other contribution, from the exactly massless superfluid ``phonon,'' has been calculated previously. We specialize to a particular form of the interaction Lagrangian, parameterized by a single coupling. We find that if we make reasonable guesses for the values of the parameters of the effective theory, the kaons have a much smaller shear viscosity than the superfluid phonons but also a much shorter mean free path, so they could easily provide the dominant contribution to the shear viscosity of CFL-K0 quark matter in a neutron star in the temperature range $0.01$ to $1$ MeV (${10}^{8}$ to ${10}^{10}$ K).}, number={2}, journal={PHYSICAL REVIEW C}, author={Alford, Mark G. and Braby, Matt and Mahmoodifar, Simin}, year={2010}, month={Feb} }
@article{braby_chao_schaefer_2010, title={Thermal conductivity and sound attenuation in dilute atomic Fermi gases}, volume={82}, ISSN={["1094-1622"]}, url={http://inspirehep.net/record/848739}, DOI={10.1103/physreva.82.033619}, abstractNote={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{sub c}, the quasiparticles are fermions, whereas below T{sub c}, the dominant excitations are phonons. We calculate the thermal conductivity in both cases. We find that at unitarity the thermal conductivity {kappa} in the normal phase scales as {kappa}{proportional_to}T{sup 3/2}. In the superfluid phase we find {kappa}{proportional_to}T{sup 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{sub 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.}, number={3}, journal={PHYSICAL REVIEW A}, author={Braby, Matt and Chao, Jingyi and Schaefer, Thomas}, year={2010}, month={Sep} }
@article{braby_chao_schaefer_2010, title={Thermal conductivity of color-flavor-locked quark matter}, volume={81}, ISSN={["1089-490X"]}, url={http://inspirehep.net/record/831992}, DOI={10.1103/physrevc.81.045205}, abstractNote={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 owing to phonons is kappa{sup (P)}approx1.04x10{sup 26} mu{sub 500}{sup 8}DELTA{sub 50}{sup -6} erg cm{sup -1} s{sup -1} K{sup -1} and the contribution of kaons is kappa{sup (K)}approx2.81x10{sup 21} f{sub p}i{sub ,100}{sup 4}T{sub MeV}{sup 1/2}m{sub 10}{sup -5/2} erg cm{sup -1} s{sup -1} K{sup -1}. 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 time scale of a few seconds.}, number={4}, journal={PHYSICAL REVIEW C}, author={Braby, Matt and Chao, Jingyi and Schaefer, Thomas}, year={2010}, month={Apr} }