Acausal Dispersion Relations and a Fundamental Length ?

We study the use of dispersion relations;modified to violate causality, as a tool to limit a fundamental acausal length. We find that unless the usual dispersion relations are found to be violated, acausal dispersion relations give no new information. This means that the only presently believable limit on an acausal length is given by dimensional analysis; since dispersion relations have been tested to incident energies of 20 BeV, any fundamental acausal length is probably less than lit/20 BeV M 10-15cm. (Submitted to The Physical Review) t Supported by the U. S. Atomic Energy Commission. * Present address: University of Maryland, College Park, Maryland 20742