English

Framed configuration spaces and exotic spheres

Algebraic Topology 2026-05-20 v2 Geometric Topology

Abstract

We determine when an exotic sphere Σ\Sigma of dimension d≢1(4)d\not \equiv 1 (4) can be detected through the homotopy type of its truncated Disc-presheaf. The latter records the diagram of framed configuration spaces of bounded cardinality in Σ\Sigma with natural point-forgetting and -splitting maps between them, and it gives rise to the finite stages in Goodwillie--Weiss' embedding calculus tower. Our proof involves three ingredients that could be of independent interest: a gluing result for Disc-presheaves of manifolds divided into two codimension zero submanifolds, a version of Atiyah duality in the context ofDisc-presheaves, and a computation of the finite residual of the mapping class group of the connected sums g(S2k+1×S2k+1)\sharp^g(S^{2k+1}\times S^{2k+1}).

Keywords

Cite

@article{arxiv.2509.19074,
  title  = {Framed configuration spaces and exotic spheres},
  author = {Manuel Krannich and Alexander Kupers and Fadi Mezher},
  journal= {arXiv preprint arXiv:2509.19074},
  year   = {2026}
}

Comments

28 pages, 1 figure, to appear in Forum of Mathematics Sigma

R2 v1 2026-07-01T05:52:12.368Z