Theory HEP Seminar

M-theory interpretation of the real topological string

Nicolo Piazzalunga

SISSA

After a short review of topological strings and Gopakumar-Vafa invariants, I'll discuss the type IIA physical realization of the unoriented topological string introduced by Walcher, its M-theory lift, and show how it allows to compute open and unoriented topological amplitudes in terms of one-loop diagrams of BPS M2-brane states. This confirms and allows to generalize the conjectured BPS integer expansion of the topological amplitude. The M-theory lift of the orientifold is freely acting on the M-theory circle, so that integer multiplicities are a weighted version of the equivariant subsector of the original closed oriented GV invariants. The M-theory lift also provides a new perspective on the topological tadpole cancellation condition (based on 1405.6019 with Angel Uranga)