Nucleon superfluidity in a core of neutron stays.

最近对中子星的表面温度观测表明，核子超流动性与“新相”（即介子凝聚相、介子凝聚相、大质子混合相等）共存，导致中子星的快速冷却。在这个研究项目中，我们的目标是系统地研究核子超流体是否可以与这些新相共存，意图在新相与超流体的相容性方面检查什么是快速冷却的真正候选者。(1) kaon凝聚相和(2)大质子混合相：我们发现这些相不太可能有核子超流动性，主要是由于与这些相相关的核子有效质量很小。这意味着“kaon冷却”和“直接URCA冷却”将被排除在快速冷却方案之外。(3)带电介子(π ^C) -凝聚相：我们将BCS理论推广到π ^C凝聚下准粒子（由n和p组成的eta）超流体的情况，发现eta之间的^3P_2对相互作用与没有介子凝聚的情况没有太大的不同，从而导致eta-超流体存在到约3rho_0 （rho_0为标准核密度）。(4)中性介子(π ^0) -凝聚相：在该相中，核子体系呈现层状结构并伴有自旋有序（称为ALS结构），提出了处理核系统低维超流体的新问题。我们根据SU(4)夸克模型，提出了一个适用于ALS态的公式，并使其适用于包括DELTA（1232）等压线在内的情况。我们发现，由于DELTA效应，超流体的存在至少延伸到4rho_0。在这些研究的基础上，我们可以说，“介子冷却”是最有希望的快速冷却方案。π ^0 π ^C组合凝聚下的超流动性是一个即将出现的课题，其中(3)和(4)的研究是重要的一步。

Coexistence of nucleon superfluidity with "new phases" (i.e., pion-condensed, kaon-condensed, large proton-mixing phases and so on) which lead to a rapid cooling scenario is suggested from recent surface-temperature observations for neutron stars. In this research project, we aim to investigate systematically whether nucleon superfluid can coexist with these new phases, intending to check what is a true candidate for the rapid cooling in terms of the compatibility of a new phase with superfluidity.(1) Kaon-condensed and (2) Large proton-mixing phases : We have found that these phases are unlikely to have nucleon superfluidity, mainly due to the small effective-mass of nucleons relevant to these phases. This means that the "kaon cooling" and the "direct URCA cooling" would be excluded from the rapid cooling scenario.(3) Charged pion (pi^C) -condensed phase : We have extended the BCS theory into the case applicable to quasi-particle (eta composed of n and p) superfluidity under pi^C condensation, and found that the ^3P_2 pairing interaction between eta's is not so different from the case without pion condensation, leading to the result that eta-superfluid exists up to about 3rho_0 (rho_0 being the standard nuclear density).(4) Neutral pion (pi^0) -condensed phase : In this phase, nucleon system takes a layred structure accompained by a spin-ordering (called ALS structure) and poses a new problem to treat a low-dimensional superfluid in nuclear system. We have presented a formulation suitable to the ALS state and made it applicable to the case including the isobar DELTA (1232) in the light of SU (4) quark model. We have found that due to the DELTA effects, the existence of superfluid is extended at least up to 4 rho_0.On the basis of these studies, we can say that the "pion cooling" is most promising for the rapid cooling scenario. The superfluidity under pi^0 pi^C combined condensate is a forthcoming subject, to which studies in (3) and (4) serve as an important step.