Probing the phases of cold ultra-dense matter using neutron star physics

Simin Mahmoodifar
Matter at very high densities and low temperatures is predicted to be in a "color superconducting" phase. At high enough densities, quark matter is in the Color-Flavor-Locked (CFL) phase, but the possible phases of matter at intermediate densities are unknown. Since the density at the core of a neutron star can be as high as a few times the nuclear saturation density, it is the most likely place to find these exotic forms of matter in the real world. The main goal of this thesis is to probe the
more » ... sis is to probe the phases of cold dense matter using neutron star physics. Studying the transport properties of different phases of dense matter that may occur in a compact star is particularly important because transport properties such as viscosity, in addition to depending on the equation of state of matter, also depend on the low-energy degrees of freedom and therefore can discriminate between different phases of dense matter more efficiently. In the first part of this thesis we calculate the mean free path and kaonic contribution to the shear viscosity of kaon-condensed color-flavor-locked (CFL-K 0 ) phase of quark matter. In the second part we calculate the large-amplitude enhancement of the bulk viscosity of dense matter. We obtain general analytic solutions as well as numerical solutions for the amplitude-dependent bulk viscosity of dense matter which are valid for any equations of state where equilibration occurs via fermions. In the third and fourth parts, we use our general results for the bulk viscosity to calculate the damping timescales of r-mode oscillations of neutron stars due to small-amplitude and large-amplitude bulk viscosity, the instability window of the r-modes and the saturation amplitude due to "supra-thermal" enhancement of the bulk viscosity for different cases of strange quark stars, hadronic stars and hybrid stars. ii
doi:10.7936/k74j0c67 fatcat:p33w3bv3jncopmwib4p2ybqk2u