Goldstone modes in the neutron star core

Abstract

We studied the effect of the diverse Goldstone boson modes in the transport properties of dense neutron matter. The two Goldstone bosons associated with density oscillations of the neutron and electron + proton fluids, called superfluid phonons, mix and couple strongly to electrons reducing their mean free time and suppressing their contribution to transport coefficients. For typical neutron star temperatures in the range T=106–109 K, the Goldstone modes associated with rotational symmetry, called angulons, couple weakly to each other and to electrons and, consequently, have anomalously large mean free paths and can contribute to both diffusive and ballistic transport of heat and momentum. Still, their contribution is smaller that coming from the electrons on account of their smaller density. We speculate that long-wavelength superfluid phonons and angulons can play a role in neutron star seismology, and lead to interesting phenomenology especially since angulons couple to magnetic fields and have anisotropic dispersion relations.