title: Phase transitions in nucleonic matter and neutron-star cooling.
abstract: A new scenario for neutron-star cooling is suggested by the correspondence between pion condensation, induced by critical spin-isospin fluctuations, and the metal-insulator phase transition in a 2D electron gas. Above the threshold density for pion condensation, the neutron single-particle spectrum acquires an insulating gap that quenches neutron contributions to neutrino production. In the liquid phase just below the transition, the fluctuations play dual roles by (i) creating a multisheeted neutron Fermi surface that extends to low momenta and activates the normally forbidden direct Urca cooling mechanism, and (ii) amplifying the nodeless P-wave neutron superfluid gap while suppressing S-wave pairing. Lighter stars without a pion-condensed core undergo slow cooling, whereas enhanced cooling occurs in heavier stars via direct Urca emission from a thin shell of the interior.
authors.affiliation: Russian Research Centre Kurchatov Institute, Moscow 123182, Russia.
authors.forename: V A
authors.initials: VA
authors.lastname: Khodel
authors.forename: J W
authors.initials: JW
authors.lastname: Clark
authors.forename: M
authors.initials: M
authors.lastname: Takano
authors.forename: M V
authors.initials: MV
authors.lastname: Zverev