Instanton counting and O-vertex

We present closed-form expressions of unrefined instanton partition functions for gauge groups of type BCD as sums over Young diagrams. For SO(n) gauge groups, we provide a fivebrane web picture of our formula based on the vertex-operator formalism of the topological vertex with a new type called O-vertex for an O5-plane.

Automated summary

The study presents closed-form expressions of unrefined instanton partition functions for gauge groups of type BCD as sums over Young diagrams. It also provides a fivebrane web picture of the formula for SO(n) gauge groups based on the topological vertex with a new type known as O-vertex for an O5-plane.