EFFECTS OF HYPERONS ON THE DYNAMICAL DECONFINEMENT TRANSITION IN COLDNEUTRON-STAR MATTER

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 an d 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 consider ed, together with the case of the system without hyperons. We find tha t strangeness contained in hyperons acts to reduce a density jump at d econfinement 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 nuc leation in the absence of hyperons, is thus shown to be of little cons equence. If the effective droplet mass is small enough to become compa rable 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 hyp erons, becomes of less importance. Independently of the presence of hy perons, the dynamical compressibility of the hadronic phase is unlikel y to affect the quantum nucleation of quark matter at temperatures fou nd in neutron star interiors. For matter with and without hyperons, we estimate the overpressure needed to form the first droplet in the sta r during the compression due to stellar spin-down or mass accretion fr om a companion star. The temperature at which a crossover from the qua ntum nucleation to the Arrhenius-type thermal nucleation takes place i s shown to be large compared with the temperature of matter in the cor e. We also determine the range of the bag-model parameters such as the bag constant, the QCD fine structure constant, and the strange quark mass where quark matter is expected to occur in the star. [S0556-2813( 98)01910-4].