Konwersatorium im. Leopolda Infelda

Existence of pulsars of mass close to two solar masses puts a strong constraint on the equation of state (EOS) of cold matter at the density significantly exceeding normal nuclear matter density (NNMD=3*10^14 g/cc). The maximum mass of neutron stars will be discussed. Theoretical EOSs involving nucleons, hyperons, and quark plasma consistent with two-solar-mass constraint will be reviewed; maximum densities reached in neutron stars will be shown to be from 7 to 10 NNMD. Then, structure of the EOS as given by the quantum chromodynamics and its approximations will be sketched. Four constraints on the EOS will be formulated and used to get an allowed strip in the pressure-density plane for the densities up 100*NNMD. Finally, prospects for the future determination of the EOS from the masses and radii of neutron stars extracted via analysing precise X-ray spectra obtained using orbital detectors planned for 2020s will be described