Topology in Dimension 4.5

Topology in Dimension 4.5

October 31–November 4, 2022 at the Banff International Research Station


This conference brought together experts in various aspects of four-dimensional topology. Themes included isotopy and concordance of surfaces in 4-manifolds and diffeomorphism groups of 4-manifolds.

The organizers of this conference were David Gay, Jason Joseph, Maggie Miller, and Hannah Schwartz.

Talk abstracts and compiled problem/question list

Abstracts        Compiled Problems

Notes and resources

Several participants kindly shared their notes prepared for the expository mini-series talks (either their research notes or talk slides).

Ryan Budney — Diffeomorphism groups of 4-manifolds (motivation and background)

Ryan Budney — Diffeomorphism groups of 4-manifolds (recent results)

Ryan Budney — How to show a barbell diffeomorphism is nontrivial (research talk)

Anthony Conway — Invariant of 2-knots (notes)

David Gabai — Dax's work on embedding spaces

Mark Powell — Concordance and isotopy invariants of surfaces (notes)

Rob Schneiderman — Three views of the Freedman–Quinn invariant

Peter Teichner — Isotopy classification of half-disks in 4-manifolds (research talk)