Căldăraru's twisted derived equivalence conjecture for K3 surfaces

Let XX) and XX' be algebraic K3 surfaces, and let αH2(X,OX)\alpha\in H^2(X,\mathcal O_X^*) and αH2(X,OX)\alpha'\in H^2(X',\mathcal O_{X'}^*) be torsion classes. Define the twisted transcendental lattices by lifting these classes to H2(X,Q)H^2(X,\mathbb Q) and H2(X,Q)H^2(X',\mathbb Q) and setting

T(X,α):=Ker(α:T(X)Q/Z),T(X,\alpha):=\operatorname{Ker}(\alpha:T(X)\to\mathbb Q/\mathbb Z),

and similarly for T(X,α)T(X',\alpha').

Căldăraru's conjecture. There exists an exact equivalence between the derived categories of twisted coherent sheaves

Db(Cohα(X))Db(Cohα(X))D^{\operatorname b}(\operatorname{Coh}_\alpha(X))\simeq D^{\operatorname b}(\operatorname{Coh}_{\alpha'}(X'))

if and only if there exists a Hodge isometry

T(X,α)T(X,α).T(X,\alpha)\cong T(X',\alpha').

This conjecture proposes a lattice-theoretic characterization of equivalence between derived categories of twisted coherent sheaves on algebraic K3 surfaces. The source notes that the analytic analogue had recently been established, while the algebraic statement was proposed by Căldăraru.

Sources & referencesView supporting material

Primary source

Daniel Huybrechts, “Generalized Calabi-Yau structures, K3 surfaces, and B-fields”, arXiv:math/0306162 (2004).

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