Luuk Verhoeven - Quantum Geometry (Math)

Luuk Verhoeven (Western University)

Title: Immersions as unbounded Kasparov products: embedding spheres inside Euclidean space

Abstract: We construct an unbounded representative for the shriek class associated to the embeddings of spheres into Euclidean space. We equip this unbounded Kasparov cycle with a connection and compute the unbounded Kasparov product with the Dirac operator on R^n+1 . We find that the resulting spectral triple for the algebra C(S^n) differs from the Dirac operator on the round sphere by a so-called index cycle, whose class in KK_0(C, C) represents the multi- plicative unit. At all points we check that our construction involving the unbounded Kasparov product is compatible with the bounded Kasparov product using Kucerovsky’s criterion and we thus capture the composition law for the shriek map for these immersions at the unbounded KK-theoretical level. The necessary KK-theory will be introduced as a black box.