Shear viscosity and thermal conductivity of nuclear “pasta”

Abstract

We calculate the shear viscosity \ensuremath{\eta} and thermal conductivity \ensuremath{\kappa} of a nuclear pasta phase in neutron star crusts. This involves complex nonspherical shapes. We use semiclassical molecular dynamics simulations involving 40, 000 to 100, 000 nucleons. The viscosity \ensuremath{\eta} can be simply expressed in terms of the height ${Z}^{*}$ and width $\ensuremath{\Delta}q$ of the peak in the static structure factor ${S}_{p}(q)$. We find that \ensuremath{\eta} increases somewhat, compared to a lower density phase involving spherical nuclei, because ${Z}^{*}$ decreases from form factor and ion screening effects. However, we do not find a dramatic increase in \ensuremath{\eta} from nonspherical shapes, as may occur in conventional complex fluids.