Electrical conductivity tensor of dense plasma in magnetic fields

Electrical conductivity of finite-temperature plasma in neutron star crusts is studied for applications in magneto-hydrodynamical description of compact stars. We solve the Boltzmann kinetic equation in relaxation time approximation taking into account the anisotropy of transport due to the magnetic field, the effects of dynamical screening in the scattering matrix element and corre- lations among the nuclei. We show that conductivity has a minimum at a non-zero temperature, a low-temperature decrease and a power-law increase with increasing temperature. Selected numerical results are shown for matter composed of carbon, iron, and heavier nuclei present in the outer crusts of neutron star.Comment: 12 pages, 5 figures, supplemental material contains 21 tables. Proceedings of "The Modern Physics of Compact Stars and Relativistic Gravity 2015", 30 September 2015 - 3 October 2015 Yerevan, Armeni

Electrical Resistivity and Hall Effect in Binary Neutron-Star Mergers

We examine the range of rest-mass densities, temperatures and magnetic fields involved in simulations of binary neutron-star mergers and identify the conditions under which the ideal-magnetohydrodynamics approximation breaks down and hence the magnetic-field decay should be accounted for. We use recent calculations of the conductivities of warm correlated plasma in envelopes of compact stars and find that the magnetic-field decay timescales are much larger than the characteristic timescales of the merger process for lengthscales down to a meter. Because these are smaller than the currently available resolution in numerical simulations, the ideal-magnetohydrodynamics approximation is effectively valid for all realistic simulations. At the same time, we find that the Hall effect can be important at low densities and low temperatures, where it can induce a non-dissipative rearrangement of the magnetic field. Finally, we mark the region in temperature and density where the hydrodynamic description breaks down.Comment: 10 pages, 4 figures, v2: minor changes, matches published version; v1: 9 page, 4 figure