Speaker
Description
Neutron stars are compact objects that can be likened to a single gigantic nucleus. Their central density exceeds nuclear density, allowing diverse states to appear that are not seen in ordinary nuclei, such as hyperon mixing, quark deconfinement and nucleon superfluidity. These states strongly affect the neutrino emission dominating neutron star cooling, thereby determining their thermal evolution. Comparisons between observed neutron star temperatures and theoretical calculations enable exploration of their internal states.
We have investigated the thermal evolution of neutron stars, taking into account the effects of colour-superconducting quark matter. Due to the degrees of freedom of quark colour and flavour, several pairing possibilities are conceivable in the colour superconducting state. We assume that the CFL (Colour Flavour Locked) or 2SC (Two-flavour superconductivity) phase appears. We also consider the effects of the 2SC+<$dd$> phase. In this phase, the ${}^3P_2$ superfluidity of neutrons in the hadron phase is succeeded by unpaired $d$ quarks in the 2SC phase. We found that incorporating the 2SC+<$dd$> phase can explain the observational results of cold neutron stars.