Wall-crossing: techniques and applications

September 15 to September 19, 2025

at the

American Institute of Mathematics, Pasadena, California

organized by

Nikolas Kuhn, Henry Liu, and Felix Thimm

Original Announcement

This workshop will be devoted to new developments in wall-crossing for enumerative invariants of abelian categories, with a focus on identifying promising applications.

Specifically, Joyce’s recent "universal" wall-crossing formalism provides a way to systematically study wall-crossing phenomena for a reasonably large class of linear categories. It generalizes previous wall-crossing formalisms of Joyce-Song and Kontsevich-Soibelman, which are controlled by Hall algebras. Strategies that have been successful there may now be applied to new enumerative settings: moduli spaces of sheaves on surfaces, Calabi-Yau 3-folds and 4-folds; for equivariant and/or K-theoretic refinements of ordinary enumerative invariants; etc. Remarkably, the new wall-crossing formula is controlled by a vertex algebra, constructed naturally and geometrically from the moduli stack, indicating new and fruitful interactions with the theory of vertex algebras.

We plan to bring together experts from enumerative geometry, mathematical physics and geometric representation theory to explore connections between these fields through the lens of these new developments.

The main topics for the workshop are:

Material from the workshop

A list of participants.

A report on the workshop activities.

Workshop videos