Effects of hyperons on the dynamical deconfinement transition in cold neutron star matter

Kei Iida, Katsuhiko Sato

Published 1998-08-20Version 1

The influence of the presence of hyperons in dense hadronic matter on the quantum nucleation of quark matter is examined at low temperatures relevant to neutron star cores. We calculate the equation of state and the composition of matter before and after deconfinement by using a relativistic mean-field theory and an MIT bag model, respectively; the case in which hyperons are present in the hadronic system is considered, together with the case of the system without hyperons. We find that strangeness contained in hyperons acts to reduce a density jump at deconfinement as well as a lepton fraction in the hadronic phase. As a result of these reductions, a quark matter droplet being in a virtual or real state has its effective mass lightened and its electric charge diminished into nearly zero. The Coulomb screening of leptons on the droplet charge, which has significance to the droplet growth after nucleation in the absence of hyperons, is thus shown to be of little consequence. If the effective droplet mass is small enough to become comparable to the height of the potential barrier, the effect of relativity brings about an exponential increase in the rate of droplet formation via quantum tunneling, whereas the role played by energy dissipation in decelerating the droplet formation, dominant for matter without hyperons, becomes of less importance. For matter with and without hyperons, we estimate the overpressure needed to form the first droplet in the star during the compression due to stellar spin-down or mass accretion from a companion star. The temperature at which a crossover from the quantum nucleation to the Arrhenius-type thermal nucleation takes place is shown to be large compared with the temperature of matter in the core.