a Institute for Theoretical Physics, University of California, Santa Barbara, CA 93106, USA
b School of Natural Sciences, Institute for Advanced Study, Olden Lane, Princeton, NJ 08540, USA
Abstract:
A study is made of the implications of heterotic string T-duality and extended gauge symmetry for the conjectured equivalence of heterotic and Type I superstrings. While at first sight heterotic string world-sheet dynamics appears to conflict with Type I perturbation theory, a closer look shows that Type I perturbation theory “miraculously” breaks down, in some cases via novel mechanisms, whenever the heterotic string has massless particles not present in Type I perturbation theory. This strongly suggests that the two theories actually are equivalent. As further evidence in the same direction, we show that the Dirichlet one-brane of Type I string theory has the same world-sheet structure as the heterotic string.