Relative orthogonal Grassmannian decomposition conjecture for quadric fibrations

Let p:QSp:\mathfrak{Q}\to S be a quadric fibration of relative dimension n+1n+1 over a smooth base, with fibers Qs\mathfrak{Q}_s of rank at least 44, where nn is odd. Let Cl0\mathcal{C}l_0 be the sheaf of even Clifford algebras associated with the quadric fibration. Relative orthogonal Grassmannian conjecture. There exists a semiorthogonal decomposition

Db(OGr(2,Q))=Db(S,Cl0),,Db(S,Cl0)n+1 times,Db(S),,Db(S)(n1)(n+1)2 times,\mathrm{D}^{\mathrm{b}}(\operatorname{OGr}(2,\mathfrak{Q}))=\left\langle\underbrace{\mathrm{D}^{\mathrm{b}}(S,\mathcal{C}l_0),\dots,\mathrm{D}^{\mathrm{b}}(S,\mathcal{C}l_0)}_{n+1\text{ times}},\underbrace{\mathrm{D}^{\mathrm{b}}(S),\dots,\mathrm{D}^{\mathrm{b}}(S)}_{\frac{(n-1)(n+1)}{2}\text{ times}}\right\rangle,

where Db(S,Cl0)\mathrm{D}^{\mathrm{b}}(S,\mathcal{C}l_0) is the derived category of the sheaf of even Clifford algebras over SS. This is presented as a natural generalization of the pencil-of-quadrics conjecture to arbitrary quadric fibrations, under a rank condition ensuring flatness. Its resolution status is not specified in the supplied text.

Sources & referencesView supporting material

Primary source

Saket Shah, “Flips for spaces of quadrics on del Pezzo varieties”, arXiv:2602.07366 (2026).

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