Galkin's lower bound conjecture for the spectral radius of quantum multiplication

For a Fano manifold XX, let QH(X):=Hev(X)QQ[q]QH^\bullet(X):=H^{\rm ev}(X)\otimes_{\mathbb{Q}}\mathbb{Q}[\mathbf{q}] be its even quantum cohomology, and let c^1\hat c_1 be quantum multiplication by c1(X)c_1(X) evaluated at q=1\mathbf{q}=1. Write ρ(c^1)\rho(\hat c_1) for the spectral radius of this operator. Galkin's lower bound conjecture.

ρ(c^1)dimX+1,\rho(\hat c_1)\geq \dim X+1,

with equality if and only if XX is isomorphic to a projective space Pn\mathbb{P}^n.

Here and throughout, the dimension is the complex dimension. The conjecture has been verified in several cases, including complex Grassmannians, Lagrangian and orthogonal Grassmannians, and Fano complete intersections in projective spaces; its general status is not resolved in the supplied source.

Sources & referencesView supporting material

Primary source

Jianxun Hu, Huazhong Ke, Changzheng Li and Lei Song, “On the quantum cohomology of blow-ups of four-dimensional quadrics”, arXiv:2502.13558 (2025).

Additional references

3 papers in this index state this conjecture (2019–2025). The statement above is taken from the most recent of them; the others are arXiv:2405.16987, arXiv:1906.11646.

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