2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/121034In 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.8 pages, no figuresHigh Energy Physics - Theorytext