O. Borisenko et al., Low-temperature expansion and perturbation theory in 2D models with unbroken symmetry: A new approach - art. no. 025013, PHYS REV D, 6202(2), 2000, pp. 5013
A new method for constructing weak coupling expansion of two-dimensional mo
dels with an unbroken continuous symmetry is developed. The method is based
on an analogy with the Abelian XY model, respects the Mermin-Wagner theore
m, and uses a link representation of the partition and correlation function
s. An expansion of the free energy and of the correlation functions at smal
l temperatures is performed and first order coefficients are calculated exp
licitly. They are proved to be path independent and infrared finite. We als
o study the free energy of the one-dimensional SU(N) model and demonstrate
a nonuniformity of the low-temperature expansion in the volume for this sys
tem. Further, we investigate the contribution of holonomy operators to the
low-temperature expansion in two dimensions and show that they do not survi
ve the large volume limit. All our results agree with the conventional expa
nsion. We discuss the applicability of our method to analysis of the unifor
mity of the low-temperature expansion in two dimensions.