On the Unbounded Picture of $KK$-Theory

Symmetry Integrability and Geometry-Methods and Applications

article

Jens Kaad¹ 

[1] Department of Mathematics and Computer Science, The University of Southern Denmark, Campusvej 55

关键词: KK-theory;    unbounded KK-theory;    equivalence relations;    bounded transform 2020 Mathematics Subject Classification 19K35;    58B34;   

DOI  :  10.3842/SIGMA.2020.082

来源: National Academy of Science of Ukraine

【 摘 要 】

In the founding paper on unbounded $KK$-theory it was established by Baaj and Julg that the bounded transform, which associates a class in $KK$-theory to any unbounded Kasparov module, is a surjective homomorphism (under a separability assumption). In this paper, we provide an equivalence relation on unbounded Kasparov modules and we thereby describe the kernel of the bounded transform. This allows us to introduce a notion of topological unbounded $KK$-theory, which becomes isomorphic to $KK$-theory via the bounded transform. The equivalence relation is formulated entirely at the level of unbounded Kasparov modules and consists of homotopies together with an extra degeneracy condition. Our degenerate unbounded Kasparov modules are called spectrally decomposable since they admit a decomposition into a part with positive spectrum and a part with negative spectrum.

【 授权许可】

Unknown