Proton decay in intersecting D-brane models

We analyze proton decay via dimension-six operators in certain GUT-like models derived from Type IIA orientifolds with D6-branes. The amplitude is parametrically enhanced by a factor of α GUT −1/3 relative to the corresponding result in four-dimensional GUTs. Nonetheless, even assuming a plausible enhancement from the threshold corrections, we find little overall enhancement of the proton decay rate from dimension-six operators, so that the predicted lifetime from this mechanism remains close to 1036 years.