We calculate the ring structure of the singular instanton Floer homology of
(S1×Σ,S1×{p1​,…,pn​}) with C-coefficients, where
Σ is a closed oriented surface. As an application, we prove an excision
formula for singular instanton homology when n=1. This settles the last unknown
case of excision formula for instanton Floer homology.Comment: 53 page