Nucleon Superfluidity under Coexistent Condensation of Neutral and Charged Pions in Neutron Matter

Abstract

Nucleon superfluidity has an important bearing on neutron star phenomena, especially coolingl) and glitches.2) In an ordinary situation the 3 P, superfluid is realized from the Fermi gas state at nucleon density p ~ (1 ~3)po, po being the nuclear density. How this aspect changes when pion condensation develops is not only an interesting problem from the viewpoint of many-body theory but also has an important relevance to the study on the relation between pion condensation and neutron star phenomena. The following two cases were investigated separately in our previous works. First, under neutral pion (7[0) condensation, superfluid becomes of two-dimensional character as a result of the Alternating-Layer-Spin (ALS) structure combined to the 7[0 condensation. ) Second, charged pion (7[C) condensation brings about serious attenuation of the 3 P, superfluidity because the pairing interaction of quasi-neutrons is weakened from the original one in neutron matter:) In this paper, extending these previous works, we study the 3 P2-dominant superfluidity in the phase resulting from pure neutron matter, where both 7[0 and 7[e condensations coexist. Tamiya and one of the present authors (R. T. )5) proposed a model that the 7[0 and 7[c condensations can coexist without interference if the momentum of condensed 7[0 (ko) and that of condensed 7[e (ke) are perpendicular. In this model, nucleons form the ALS structure ) along ko (taken as kocx i) as the source of condensed 7[0 and the 7[e condensation takes place in the layers where nucleons are in the two-dimensional Fermi gas states. By using the 7[-N P-wave interaction, they showed that the energy gains due to two condensations are additive. Since, even for more realistic interactions, the critical density of the7[e condensations7),8) are not so different from that of 7[0 condensation,)O) such coexistent condensation (denoted hereafter by 7[07[e condensation) is expected to possibly occur in neutron star interior.