The short distance behaviour of massive integrable quantum field theories is
analyzed in terms of the form factor approach. We show that the on-shell
dynamics is compatible with different definitions of the stress-energy tensor
Tμν​(x) of the theory. In terms of form factors, this is equivalent to
having a possible non-zero matrix element F1​ of the trace of Tμν​ on
one-particle state. Each choice of F1​ induces a different scaling behaviour
of the massive theory in the ultraviolet limit.Comment: 32 pages LATEX file (Three figures not included in the text)
ISAS/EP/93/6