Functoriality conjecture for wrong-way maps in KK-bordism theory

From papers

Let f:XYf:X\to Y and g:YZg:Y\to Z be two KK-oriented smooth maps. Write Ω!(gf)Ω(Cc(X),C0(Z))\Omega_!(g\circ f)\in \Omega_*(C^\infty_c(X),C_0(Z)) for the wrong-way class, and let (\mathpzcEf,Df)(\mathpzc{E}_f,D_f) and (\mathmathpzcEg,Dg)(\mathmathpzc{E}_g,D_g) be the cycles associated with ff and gg. For a geometrically defined connection \nabla, consider their constructive unbounded Kasparov product.

Functoriality conjecture. The class Ω!(gf)\Omega_!(g\circ f) should be identified, up to a canonical bordism, with

(\mathpzcEfC0(Y)\mathpzcEg,Df1\mathpzcEg+1Dg),(\mathpzc{E}_f\otimes_{C_0(Y)}\mathpzc{E}_g,D_f\otimes 1_{\mathpzc{E}_g}+1\otimes_\nabla D_g),

and there should be a canonical bordism

(\mathpzcEfC0(Y)\mathpzcEg,Df1\mathpzcEg+1Dg)bor(\mathpzcEgf,Dgf).(\mathpzc{E}_f\otimes_{C_0(Y)}\mathpzc{E}_g,D_f\otimes 1_{\mathpzc{E}_g}+1\otimes_\nabla D_g)\sim_{\rm bor}(\mathpzc{E}_{g\circ f},D_{g\circ f}).

The claim expresses functoriality of wrong-way maps in KKKK-bordism theory: composition of KK-oriented smooth maps is represented by the constructive unbounded Kasparov product, up to a canonical bordism. The surrounding argument establishes the required bordism in the setting considered, but the scope of the general assertion beyond that construction is not specified in the supplied text.

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Sources & referencesView supporting material

Primary source

Robin J. Deeley, Magnus Goffeng and Bram Mesland, “Bordisms and unbounded KK-theory”, arXiv:2603.26450 (2026).

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