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Sz-Sheng Wang (National Yang Ming Chiao Tung University)
2026-04-29  10:50 - 11:50
Room 202, Astronomy and Mathematics Building

A Type II extremal transition $Y \searrow X$ of smooth projective $3$-folds consists of a crepant extremal divisorial contraction $\phi \colon Y \to \bar{Y}$ with curve class $\ell \in \mathrm{NE}(Y)$ and \dim \phi(\mathrm{Exc}(\phi))=0, followed by a smoothing $\bar{Y} \rightsquigarrow X$. In this talk, I will describe how the quantum cohomology $QH(X)$ is obtained from $QH(Y)$ via analytic continuation, regularization, and specialization in $Q^{\ell}$. Besides roots of unity, special L-values appear in $\lim Q^{\ell}$ whenever $\bar Y$ admits more than one smoothing. This is joint work with Shuang-Yen Lee and Chin-Lung Wang.