Hyperon-quark mixed phase in dense matter

Maruyama, Toshiki  ; Chiba, Satoshi; Schulze, H.-J.*; Tatsumi, Toshitaka*

Quark matter has been expected inside compact stars. Since the deconfinement transition from hadron to quark phase may occur as a first-order phase transition, the hadron-quark mixed phase should appear, where charge density as well as baryon number density is no more uniform. Owing to the interplay of the Coulomb interaction and the surface tension, the mixed phase can have an exotic shape called pasta structure. In a series of recent papers we have revealed an important role of the charge screening effect in the mixed phase. In this presentation, we incorporate a realistic EOS of hadronic matter which properly includes hyperon degree of freedom and discuss the properties of hadron-quark mixed phase in compact stars. Taking into account the charge screening effects on pasta structures of hyperon-quark mixed phase, we find that the resultant EOS is not so different from that given by the Maxwell construction (MC). Thereby the bulk properties of compact stars such as the mass-radius relation are little affected, compared with the MC case. However, the internal properties of the mixed phase are very different in two cases, especially about hyperons: hyperons always appear in the mixed phase in the MC case, while no hyperon in our case. Non-uniform structure and suppression of hyperons in the mixed phase should have some implications on the neutrino transport and cooling of pulsars as well as the maximum mass problem.