  In this short note, we report a curious appearance of the recently discovered
4d-5d connection of extremal blackholes in the topological string B-model. The
holomorphic anomaly equations in the Schrodinger-Weil representation are
written {\it formally} in terms of M2 charges. In the phase space the 4d-5d
charges are related by a non-linear canonical transformation. The blackhole
partition function factors into M2-anti-M2 contributions in leading
approximation.

High Energy Physics - Theory