Concrete uncountable Moore–Schmidt conjecture

Let Γ\Gamma be a discrete group acting concretely on a measure space X=(X,X,μ)X=(X,\mathcal{X},\mu), and let KK be a compact Hausdorff abelian group. A concrete KBaK_{\mathcal{B}a}-valued cocycle on XX is a family ρ=(ργ)γΓ\rho=(\rho_\gamma)_{\gamma\in\Gamma}. Concrete uncountable Moore–Schmidt conjecture. The cocycle ρ\rho is a concrete coboundary if and only if the T\mathbb{T}-valued concrete cocycles k^ρ=(k^ργ)γΓ\hat{k}\circ\rho=(\hat{k}\circ\rho_\gamma)_{\gamma\in\Gamma} are concrete coboundaries for all k^K^\hat{k}\in\hat K. The only-if direction is easy; the if direction is the unresolved part, arising from the gap between abstract and concrete measurable maps.

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Primary source

Asgar Jamneshan and Terence Tao, “An uncountable Moore-Schmidt theorem”, arXiv:1911.12033 (2022).

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