We derive nonperturbative flow equations within an effective constituent
quark model for two quark flavors. Heat-kernel methods are employed for a
renormalization group improved effective potential. We study the evolution of
the effective potential with respect to an infrared cutoff scale k at
vanishing temperature. At the first stage we omit corrections coming from the
anomalous dimension. This investigation is extrapolated to finite temperature,
where we find a second order phase transition in the chiral limit at Tc​≈130 MeV. Due to a smooth decoupling of massive modes, we can directly
link the low-temperature four-dimensional theory to the three-dimensional
high-temperature theory and can determine universal critical exponents.Comment: 17 pages including 7 figures, LaTeX, uses epsf.sty. Talk given by the
first author at Research Workshop on Deconfinement at Finite Temperature and
Density, JINR Dubna, Russia, October 1-29, 199
