  In this thesis, I study the phase diagram of dense, locally neutral
three-flavor quark matter as a function of the strange quark mass, the quark
chemical potential, and the temperature, employing a general nine-parameter
ansatz for the gap matrix. I also study the phase diagram of dense, locally
neutral three-flavor quark matter within the framework of a Nambu-Jona-Lasinio
(NJL) model. In the analysis, dynamically generated quark masses are taken into
account self-consistently. The phase diagram in the plane of temperature and
quark chemical potential is presented. In addition, I study the effect of
neutrino trapping on the phase diagram of dense, locally neutral three-flavor
quark matter within the same NJL model. The phase diagrams in the plane of
temperature and quark chemical potential, as well as in the plane of
temperature and lepton-number chemical potential are presented. The
implications of these results for the evolution of protoneutron stars are
briefly discussed.
