Constraining phases of quark matter with studies of r-mode damping in neutron stars
Abstract
The r-mode instability in rotating compact stars is used to constrain the phase of matter at high density. The color-flavor-locked phase with kaon condensation (CFL-K0) and without (CFL) is considered in the temperature range 108K < T <1011 K. While the bulk viscosity in either phase is only effective at damping the r-mode at temperatures T > 1011 K, the shear viscosity in the CFL-K0 phase is the only effective damping agent all the way down to temperatures T > 108 K characteristic of cooling neutron stars. However, it cannot keep the star from becoming unstable to gravitational wave emission for rotation frequencies f ~ 56-11 Hz at T ~ 108-109 K. Stars composed almost entirely of CFL or CFL-K0 matter are ruled out by observation of rapidly rotating neutron stars, indicating that dissipation at the quark-hadron interface or nuclear crust interface must play a key role in damping the instability.