出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：For a QCD chiral critical point to exist, the parameter region of small quark masses for which the
finite temperature transition is first-order must expand when the chemical potential is turned on.
This can be tested by a Taylor expansion of the critical surface (mu,d,ms)c(m). We present a new
method to perform this Taylor expansion numerically, which we first test on an effective model of
QCD with static, dense quarks. We then present the results for QCD with 3 degenerate flavors. For
a lattice with Nt = 4 time-slices, the first-order region shrinks as the chemical potential is turned
on. This implies that, for physical quark masses, the analytic crossover which occurs at m = 0
between the hadronic and the plasma regimes remains crossover in the m-region where a Taylor
expansion is reliable, i.e. m . T. We present preliminary results from finer lattices indicating that
this situation persists, as does the discrepancy between the curvature of Tc(mc(m = 0),m) and the
experimentally observed freeze-out curve.
