Effective tachyon dynamics in superstring theory

A recently proposed \ell=\infty field theory model of tachyon dynamics forunstable bosonic D-branes has been shown to arise as the two-derivativetruncation of (boundary)-string field theory. Using an \ell\to \infty limitappropriate to stable kinks we obtain a model for the tachyon dynamics onunstable D-branes or D-brane anti-D-brane pairs of superstring theory. Thetachyon potential is a positive definite even function of the tachyon, and atthe stable global minima there is no on-shell dynamics. The kink solutionmimics nicely the properties of stable D-branes: the spectrum of the kinkconsists of infinite levels starting at zero mass, with spacing double thevalue of the tachyon mass-squared. It is natural to expect that this model willarise in (boundary) superstring field theory.Comment: 10 pages, 1 figure, LaTe