  We investigate the finite-temperature behavior of the Yukawa model in which
$N_{f}$ fermions are coupled with a scalar field $\phi$ in the limit $N_f \to
\infty$. Close to the chiral transition the model shows a crossover between
mean-field behavior (observed for $N_f = \infty$) and Ising behavior (observed
for any finite $N_f$). We show that this crossover is universal and related to
that observed in the weakly-coupled $\phi^4$ theory. It corresponds to the
renormalization-group flow from the unstable Gaussian fixed point to the stable
Ising fixed point. This equivalence allows us to use results obtained in field
theory and in medium-range spin models to compute Yukawa correlation functions
in the crossover regime.

High Energy Physics - Lattice