Shigehiro Yasui (HU) P-wave superfluids in neutron stars
Neutron stars are compact stars, whose mass is about 1.5-2 times as heavy as the sun and the radius is about 10 km. Despite the smallness, the neutron stars provide us with unusual structure of matter in extreme environments. The strong gravity of the neutron stars compresses atoms to resolve to unusual matter state, called neutron matter, which is mainly composed of neutrons with small admixture of protons and electrons. This state resembles the electrons gas in condensed matter. In contrast to the Coulomb force for electrons, however, the neutrons are governed by nuclear forces whose properties are drastically changed from low pressure at surface of neutron stars to high pressure inside, and it provides us with rich phase diagrams in neutron matter. In my presentation, I focus on the P-wave interaction between two neutrons at high pressure, and discuss the attraction induces the neutron P-wave superfluids like He3 gas in condensed matter. Especially, the nuclear force, dependent on the combination of angular momentum and total spin in the neutron pairing, realizes the various matter phases according to the symmetry breaking patterns for temperature, magnetic fields, rotations, and so on. As interesting properties, I also introduce topology existing in neutron P-wave superfluids, and discuss the resemblance and/or differences with condensed matter, such as liquid crystals and He3.