Finite generation conjecture for diffeomorphism groups of closed manifolds

Let XX be a smooth closed manifold. Write Diff(X)\mathrm{Diff}(X) for its diffeomorphism group, BDiff(X)B\mathrm{Diff}(X) for its classifying space, and πk\pi_k and Hk(;Z)H_k(-;\mathbb{Z}) for homotopy and integral homology groups. Finite generation conjecture. If π1(X)\pi_1(X) is finite and dimX4\dim X\neq 4, then

πk(Diff(X)) and Hk(BDiff(X);Z)\pi_k(\mathrm{Diff}(X))\text{ and }H_k(B\mathrm{Diff}(X);\mathbb{Z})

should be finitely generated for all k0k\geq 0. No counterexample is currently known; the conjecture concerns finiteness phenomena for diffeomorphism groups and their classifying spaces outside dimension four, under a finite fundamental-group hypothesis.

Sources & referencesView supporting material

Primary source

Hokuto Konno, “Diffeomorphism groups and gauge theory for families”, arXiv:2604.15087 (2026).

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