Informal Pizza Seminar

D-strings, Supergravity Cosmic Strings and Fermion Zero Modes

Anne-Christine Davis

Cambridge & DAMTP

Recent developments in string theory suggest that cosmic strings could be formed at the end of brane inflation. Supergravity provides a realistic model to study the properties of such strings. The presence of gravity introduces significant complications. Fermion zero modes are a generic feature of cosmic strings in supersymmetric models. The corresponding massless currents can give rise to stable string loops (vortons), though the vorton density in our universe is strongly constrained. We investigate the existence of fermion zero modes on cosmic strings in supergravity theories, showing that some (but not all) zero modes disappear. This weakens the constraints on cosmic string models. In particular, winding number one cosmic D-strings in models of brane inflation are not subject to vorton constraints.