We present new strong-coupling series for O(N) spin models in three dimensions, on the cubic and diamond lattices. We analyze these series to investigate the two-point Green's function G(x) in the critical region of the symmetric phase. This analysis shows that the low-momentum behavior of G(x) is essentially Gaussian for all N from zero to infinity. This result is also supported by a large-N analysis.
@article{arxiv.hep-lat/9607066,
title = {Critical behavior of the correlation function of three-dimensional O(N) models in the symmetric phase},
author = {Massimo Campostrini and Paolo Rossi and Andrea Pelissetto and Ettore Vicari},
journal= {arXiv preprint arXiv:hep-lat/9607066},
year = {2009}
}