New data for the two-dimensional J1-J2 model shows that the critical points for singlet and triplet excitations near J2/J1=0.38 are very close together, or coincident. We propose that this is a more general result: in strongly frustrated spin systems the critical dynamics of singlet and triplet excitations are closely related. An effective field theory for such a critical point, or points, is developed, and its implications discussed. The analysis suggests the existance of gapless or almost gapless singlet excitations in the magnetically disordered phase.
@article{arxiv.cond-mat/0111025,
title = {Critical dynamics of singlet and triplet excitations in strongly frustrated spin systems},
author = {O. P. Sushkov and J. Oitmaa and Zheng Weihong},
journal= {arXiv preprint arXiv:cond-mat/0111025},
year = {2009}
}