2026/04/30 by Alexander Kupers, Mark Powell
Mathematics · #math.GT #math.AT
It is not known whether the realisation part of the s-cobordism theorem holds for smooth 4-manifolds, nor whether every pair of smoothly h-cobordant 4-manifolds is also smoothly s-cobordant. We provide some new conditions under which these questions admit a positive answer. We also give conditions under which the `standard' method to construct an h-cobordism with specified torsion cannot work.