Parreira J. R., Bolina O., Perez J. F.
Energy Gap in Heisenberg Antiferromagnetic Half-Integer Spin Chains
with Long-Range Interactions
(10K, TeX)

ABSTRACT.  We show that there is no gap in the excitation spectrum of
antiferromagnetic chains with half-integer spins and long-range
interactions provided the exchange function has a sufficiently
rapid decay