### Swarup Gadde

University of Melbourne

### Canonical decompositions of groups and 3-manifolds

**Friday 10th September, 12:05-12:55pm,
Carslaw 175. **
(Joint work with Peter Scott)

We discuss the analogues for groups of JSJ-decompositions of
Haken 3-manifolds. A key new ingredient is the analogue of regular
neighbourhoods in group theory. The analogues of imbeddings and
immersions are already known; these correspond to splittings of groups
over particular subgroups and almost invariant sets over subgroups.