Extremality conjecture for the variable quantum local system of Fano varieties

Let XX be a Fano variety of dimension nn, and let V=VfVv\mathbb{V}=\mathbb{V}_f\oplus\mathbb{V}_v be the local system associated with its regularised quantum D\mathcal{D}-module, with variable part Vv\mathbb{V}_v. Let Hprim(n/2,n/2)(X)H^{(n/2,n/2)}_{\operatorname{prim}}(X) be the space of middle-dimensional primitive Hodge classes on XX.

Extremality conjecture.

rk(IH1(P1,Vv))dim(Hprim(n/2,n/2)(X)).\operatorname{rk}\bigl(\operatorname{IH}^1(\mathbb{P}^1,\mathbb{V}_v)\bigr)\leq \dim\bigl(H^{(n/2,n/2)}_{\operatorname{prim}}(X)\bigr).

In particular, Vv\mathbb{V}_v is extremal for odd nn.

Here extremality means that the intersection cohomology group vanishes, equivalently 2rk(Vv)=rf(Vv)2\operatorname{rk}(\mathbb{V}_v)=\operatorname{rf}(\mathbb{V}_v). The supplied text gives no resolution status.

Sources & referencesView supporting material

Primary source

Mikhail Ovcharenko, “On Arithmetic Mirror Symmetry for smooth Fano fourfolds”, arXiv:2604.26592 (2026).

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