Hyperons in Neutron Stars

Abstract

In this work I briefly review some of the effects of hyperons on the properties of neutron and proto-neutron stars. In particular, I revise the problem of the strong softening of the EoS, and the consequent reduction of the maximum mass, induced by the presence of hyperons, a puzzle which has become more intringuing and difficult to solve due the recent measurements of the unusually high masses of the millisecond pulsars PSR J1903+0327 ($1.667\pm 0.021 M_\odot$), PSR J1614-2230 ($1.97 \pm 0.04 M_\odot$), and PSR J0348+0432 ($2.01 \pm 0.04 M_\odot$). Some of the solutions proposed to tackle this problem are discussed. Finally, I re-examine also the role of hyperons on the cooling properties of newly born neutron stars and on the so-called r-mode instability.