A Fixed point can hide another one; The Nonperturbative behavior of the tetracritical fixed point of the O(N) models at large N

O(N)模型の4重臨界固定点の非摂動的振る舞い

藪中 俊介; Delamotte, B.*

Yabunaka, Shunsuke; Delamotte, B.*

We show that at and below its upper critical dimension, , the critical and tetracritical behaviors of the models are associated with the same renormalization group fixed point (FP) potential. Only their derivatives make them different with the subtleties that taking their limit and deriving them do not commute and that two relevant eigenperturbations show singularities. This invalidates both the - and the - expansions. We also show how the Bardeen-Moshe-Bander line of tetracritical FPs at and can be understood from a finite- analysis.