摘要
Ⅰ. INTRODUCTION Whether in particle physics or in statistical physics, N-component field has aroused more and more interest. D. A. Kirzhnits and A. D. Linde have discussed the vacuum of the N-component field, and some authors, such as S. K. Ma and S. Coleman et al., applied the technology of 1/N expansion to the calculation of the critical exponents in phase transition But so far there have been only asymptotic
