The conjecture on moduli spaces of semiorthogonal decompositions for families of dg categories

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Let D\mathcal{D} be a family of smooth and proper dg categories over an excellent scheme UU. For a quasicompact and semiseparated scheme VV with a morphism ϕ ⁣:V→U\phi\colon V\to U, write DV\mathcal{D}_V for the base change of the family and let a VV-linear semiorthogonal decomposition be a decomposition of Perf⁡(DV)\operatorname{Perf}(\mathcal{D}_V) into admissible VV-linear subcategories.

Moduli-space conjecture. There exists an étale algebraic space SOD⁡D/U\operatorname{\mathsf{SOD}}_{\mathcal{D}/U} over UU with a functorial bijection

SOD⁡D/U(ϕ)≃{V-linear semiorthogonaltextdecompositionsPerf⁡(DV)=⟨A,B⟩}\operatorname{\mathsf{SOD}}_{\mathcal{D}/U}(\phi)\simeq\left\{\begin{array}{c}V\text{-linear semiorthogonal}\\text{decompositions }\operatorname{Perf}(\mathcal{D}_V)=\langle\mathcal{A},\mathcal{B}\rangle\end{array}\right\}

for every such ϕ ⁣:V→U\phi\colon V\to U.

This predicts that semiorthogonal decompositions in smooth and proper dg-category families form an étale algebraic moduli space, extending the previously constructed moduli space for families arising from schemes. The conjecture is presented as a generalization suggested by the algebraicity results established earlier in the paper; its resolution is not specified in the supplied text.

References

Primary source

Pieter Belmans, Shinnosuke Okawa and Andrea T. Ricolfi, “Moduli spaces of semiorthogonal decompositions in families”, arXiv:2002.03303 (2025).

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