Breather boundary form factors in sine-Gordon theory

A previously conjectured set of exact form factors of boundary exponential operators in the sinh-Gordon model is tested against numerical results from boundary truncated conformal space approach in boundary sine-Gordon theory, related by analytic continuation to sinh-Gordon model. We find that the numerical data strongly support the validity of the form factors themselves: however, we also report a discrepancy in the case of diagonal matrix elements, which remains unresolved for the time being. (C) 2011 Elsevier B.V. All rights reserved.