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SUMMARY:Obstructing isotopies between surfaces in four-manifolds - Hannah 
 Schwartz\, MPI Bonn
DTSTART:20191127T160000Z
DTEND:20191127T170000Z
UID:TALK127051@talks.cam.ac.uk
CONTACT:Ivan Smith
DESCRIPTION:We will first construct pairs of homotopic 2-spheres smoothly 
 embedded in a 4-manifold that are smoothly equivalent (via an ambient diff
 eomorphism preserving homology) but not even topologically isotopic. Indee
 d\, these examples show that Gabai's recent "4D Lightbulb Theorem" does no
 t hold without the 2-torsion hypothesis. We will proceed to discuss two di
 stinct ways of obstructing such an isotopy\, as well as related invariants
  which can be used to obstruct an isotopy between pairs of properly embedd
 ed disks (rather than spheres) in a 4-manifold. 
LOCATION:MR13
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