Non-BPS States in Heterotic - Type IIA Duality
O. Bergman, M. R. Gaberdiel
TL;DR
This paper extends heterotic--Type IIA duality to non-BPS sectors by identifying a non-BPS D-string and a non-BPS D-molecule in IIA on the orbifold limit of K3 with perturbative non-BPS heterotic states on $T^4$. It establishes the duality map through a sequence of S- and T-dualities, compares BPS spectra to validate the duality, and analyzes stability regions for the non-BPS states across moduli space. Although non-BPS masses are not protected and need not match exactly, the authors find non-vanishing regions of stability in both theories and provide a geometric interpretation via wrapped membranes in the smooth K3 limit. The work suggests a K-theory perspective and motivates further study of non-BPS D-branes in orbifolds/orientifolds and their dual heterotic descriptions.
Abstract
The relation between some perturbative non-BPS states of the heterotic theory on T^4 and non-perturbative non-BPS states of the orbifold limit of type IIA on K3 is exhibited. The relevant states include a non-BPS D-string, and a non-BPS bound state of BPS D-particles (`D-molecule'). The domains of stability of these states in the two theories are determined and compared.