title: Rearrangement of the Fermi Surface of Dense Neutron Matter and the Direct Urca Cooling of Neutron Stars.
abstract: It is proposed that a rearrangement of single-particle degrees of freedom may occur in a portion of the quantum-fluid interior of a neutron star. Such a rearrangement is associated with the pronounced softening of the spin-isospin collective mode which, under increasing density, leads to pion condensation. Arguments and estimates based on fundamental relations of many-body theory show that one realization of this phenomenon could produce very rapid cooling of the star via a direct nucleon Urca process displaying a T5 dependence on temperature.
authors.initials: DN
authors.lastname: Voskresensky
authors.initials: VA
authors.lastname: Khodel
authors.initials: MV
authors.lastname: Zverev
authors.initials: JW
authors.lastname: Clark