%0 Journal Article
%T M-theory interpretation of the real topological string
%A Nicol¨° Piazzalunga
%A Angel Uranga
%J Mathematics
%D 2014
%I arXiv
%R 10.1007/JHEP08(2014)054
%X We describe the type IIA physical realization of the unoriented topological string introduced by Walcher, describe its M-theory lift, and show that it allows to compute the open and unoriented topological amplitude in terms of one-loop diagram 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 Gopakumar-Vafa invariants. The M-theory lift also provides new perspective on the topological tadpole cancellation conditions. We finally comment on the M-theory version of other unoriented topological strings, and clarify certain misidentifications in earlier discussions in the literature.
%U http://arxiv.org/abs/1405.6019v2