Künneth conjecture for Čech homology of product cosheaves

Let MM be a manifold, let ll be a positive integer, and let k1,,klk_1,\ldots,k_l be degrees. For a cover U\mathcal{U} of MlM^l, suppose that every intersection of elements of U\mathcal{U} is diffeomorphic to a finite union of Euclidean spaces. Denote by Zk1^^ZklZ^{k_1} \mathbin{\widehat{\otimes}} \dots \mathbin{\widehat{\otimes}} Z^{k_l} the corresponding product cosheaf on MlM^l. Künneth conjecture.

Hˇ(U,Zk1^^Zkl)Hˇ(M,Zk1)^^Hˇ(M,Zkl).\check{H}_\bullet(\mathcal{U}, Z^{k_1} \mathbin{\widehat{\otimes}} \dots \mathbin{\widehat{\otimes}} Z^{k_l}) \cong \check{H}_\bullet(M, Z^{k_1}) \mathbin{\widehat{\otimes}} \dots \mathbin{\widehat{\otimes}} \check{H}_\bullet(M, Z^{k_l}).

This is the expected Künneth formula for the topological Čech homology of the product cosheaves. The preceding discussion explains that product covers are not generally cofinal among covers of MlM^l, so the formula cannot be obtained directly from the projective-limit description; its validity is left open in the paper.

Sources & referencesView supporting material

Primary source

Lukas Miaskiwskyi, “Continuous cohomology of gauge algebras and bornological Loday-Quillen-Tsygan theorems”, arXiv:2206.08879 (2022).

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