出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：We investigate the Yukawa model in which Nf fermions are coupled with a scalar field f through
a Yukawa interaction. The phase diagram is rather well understood. If the fermions are massless,
there is a chiral transition at Tc: for T < Tc chiral symmetry is spontaneously broken. At Nf =
¥ the transition is mean-field like, while, for any finite Nf , standard arguments predict Ising
behavior. This apparent contradiction has been explained by Kogut et al., who showed by scaling
arguments and Monte Carlo simulations that in the large-Nf limit the width of the Ising critical
region scales as a power of 1/Nf , so that only mean-field behavior is observed for Nf strictly
equal to infinity. We will show how the results of Kogut et al. can be recovered analytically in the
framework of a generalized 1/Nf expansion. The method we use is a simple generalization of the
method we have recently applied to a two-dimensional generalized Heisenberg model.
