We argue that the space-time uncertainty relation of the form $\Delta X\Delta T\gtrsim {\alpha }^{\prime }$ for the observability of the distances with respect to time, $\Delta T$, and space, $\Delta X$, 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.

• Received 12 November 1996

DOI:https://doi.org/10.1103/PhysRevLett.78.1219