Abstract
Recent theoretical work has led to closed form expressions for the thermodynamic functions which characterize complicated multricritcal phenomeana. Renormalization group recursion relations are used to map multicritical systems out of the critical regime, at which point Landau theory with fluctuation corrections can be employed. We review here applications of this approach to tricritical points, spin flop transitions, dipolar systems, and Heisenberg ferromagnets below Tc. Although the calculations have presently been carried out only to first order ε=4−d, they nevertheless give a good qualtiative understanding of multicritical behavior. In particular, they provide a detailed picture of the crossover between competing kinds of critical behavior, and allow treatment of ordered phases with spontaneously broken symmetries.