Pointlike D-brane Dynamics and Space-Time Uncertainty Relation

We argue that the space-time uncertainty relation of the form ΔXΔTα^' for the observability of the distances with respect to time, ΔT, and space, ΔX, is universally valid in string theory including D-branes. This relation has been previously proposed by one (T. Y.) of the present authors as a simple qualitative representation of the perturbative short-distance structure of fundamental string theory. We show that the relation, combined with the usual quantum mechanical uncertainty principle, explains the key qualitative features of D-particle dynamics.