geometry-topology / Algebraic geometry; Fano manifolds and rational curves

The generalized Mukai conjecture on Picard number and pseudoindex of Fano manifolds

Theorem 1.1: every smooth connected complex projective Fano manifold of positive dimension nn has ρX(ιX−1)≤n\rho_X(\iota_X-1)\le n, with equality if and only if X≅(PιX−1)ρXX\cong(\mathbb P^{\iota_X-1})^{\rho_X}. Consequently Mukai's original index version also holds. The paper treats smooth complex Fano manifolds only: singular (Q\mathbb Q-factorial Gorenstein) Fano varieties beyond the known toric, horospherical and spherical cases, and positive characteristic, are not covered.

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geometry-topologySep 24, 2026Significance 32/100Registry: unreviewed

The generalized Mukai conjecture on Picard number and pseudoindex of Fano manifolds

Prior state unknown→proved

Theorem 1.1: every smooth connected complex projective Fano manifold of positive dimension nn has ρX(ιX−1)≤n\rho_X(\iota_X-1)\le n, with equality if and only if X≅(PιX−1)ρXX\cong(\mathbb P^{\iota_X-1})^{\rho_X}. Consequently Mukai's original index version also holds. The paper treats smooth complex Fano manifolds only: singular (Q\mathbb Q-factorial Gorenstein) Fano varieties beyond the known toric, horospherical and spherical cas…

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Theorem 1.1: every smooth connected complex projective Fano manifold of positive dimension nn has ρX(ιX−1)≤n\rho_X(\iota_X-1)\le n, with equality if and only if X≅(PιX−1)ρXX\cong(\mathbb P^{\iota_X-1})^{\rho_X}. Consequently Mukai's original index version also holds. The paper treats smooth complex Fano manifolds only: singular (Q\mathbb Q-factorial Gorenstein) Fano varieties beyond the known toric, horospherical and spherical cases, and positive characteristic, are not covered.

Theorem 1.1: every smooth connected complex projective Fano manifold of positive dimension nn has ρX(ιX−1)≤n\rho_X(\iota_X-1)\le n, with equality if and only if X≅(PιX−1)ρXX\cong(\mathbb P^{\iota_X-1})^{\rho_X}. Consequently Mukai's original index version also holds. The paper treats smooth complex Fano manifolds only: singular (Q\mathbb Q-factorial Gorenstein) Fano varieties beyond the known toric, horospherical and spherical cases, and positive characteristic, are not covered.

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