A COMPARED ANALYSIS OF THE SUSCEPTIBILITY IN THE O(N) THEORY

作者：Branchina Vincenzo^*; Messina Emanuele; Zappala Dario

来源：International Journal of Modern Physics A, 2013, 28(17): 1350078.

DOI：10.1142/S0217751X13500784

• O(N) model
• susceptibility
• ordered phase
• infrared divergences
• renormalization group

The longitudinal susceptibility chi(L) of the O(N) theory in the broken phase is analyzed by means of three different approaches, namely the leading contribution of the 1/N expansion, the Functional Renormalization Group flow in the Local Potential approximation and the improved effective potential via the Callan-Symanzik equations, properly extended to d = 4 dimensions through the expansion in powers of epsilon = 4 - d. The findings of the three approaches are compared and their agreement in the large N limit is shown. The numerical analysis of the Functional Renormalization Group flow equations at small N supports the vanishing of chi(-1)(L) in d = 3 and d = 3.5 but is not conclusive in d = 4, where we have to resort to the Callan-Smanzik approach. At finite N as well as in the limit N -%26gt; infinity, we find that chi(-1)(L) vanishes with J as J(epsilon/2) for epsilon %26gt; 0 and as (ln(J))(-1) in d = 4.

• 出版日期2013-7-10