Krause's ideal-theoretic reformulation of the telescope conjecture

Let D\mathcal{D} be a compactly generated triangulated category, and let t=(X,Y)\mathbf{t}=(\mathcal{X},\mathcal{Y}) be a smashing semiorthogonal decomposition of D\mathcal{D}. Let Dc\mathcal{D}^c denote the compact objects, and let ItI_{\mathbf{t}} be the ideal of Dc\mathcal{D}^c consisting of morphisms α ⁣:CC\alpha\colon C\to C' such that

D(α,Y) ⁣:D(C,Y)D(C,Y)\mathcal{D}(\alpha,Y)\colon\mathcal{D}(C',Y)\to\mathcal{D}(C,Y)

is zero for every YYY\in\mathcal{Y}.

Krause's reformulated telescope conjecture. The ideal ItI_{\mathbf{t}} is generated by identity morphisms of objects in Dc\mathcal{D}^c.

Krause's reformulation is equivalent to the compact-generation formulation because the decomposition is compactly generated precisely when its associated ideal is generated by such identities. It is refuted in the same generality as the telescope conjecture.

Sources & referencesView supporting material

Primary source

Lorenzo Martini, Carlos E. Parra, Manuel Saorín and Simone Virili, “Locally finitely presented Grothendieck categories with a flat generator”, arXiv:2508.00670 (2025).

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