Recent progress in neutron star theory

We review recent progress in the theory of neutron stars and compare its pr edictions with the observational data on masses, radii, and temperatures. T he theory of neutron stars made up of neutrons, protons, and leptons is dis cussed in detail along with recent models of nuclear forces and modern many -body techniques. The possibilities of pion and kaon condensation in dense neutron star matter are considered, as is the possible occurrence of strang e hyperons and quark-matter drops in the stellar core. The structure of mix ed-phase matter in neutron stars, as well as the probable effect of phase t ransitions on the spin down of pulsars, is also discussed.