Campana–Cao–Matsumura's slope rationally connected quotient conjecture

Let XX be a smooth projective variety and let DD be an effective cmathbbQcmathbb{Q}-divisor on XX. Assume that (X,D)(X,D) is klt and that (KX+D)-(K_X+D) is nef. An orbifold morphism is a morphism of orbifold pairs; write it as

ρ:(X,D)(R,DR).\rho:(X,D)\longrightarrow(R,D_R).

Campana–Cao–Matsumura's conjecture. There exists an orbifold morphism ρ:(X,D)(R,DR)\rho:(X,D)\to(R,D_R) such that:

  1. (R,DR)(R,D_R) is a klt pair and c1(KR+DR)=0c_1(K_R+D_R)=0.
  2. For a general point rRr\in R, the general fiber (Xr,Dr)(X_r,D_r) is slope rationally connected.
  3. ρ\rho is locally trivial with respect to pairs.

This conjecture predicts a structural quotient for klt pairs with nef anticanonical divisor. It is known for smooth surfaces, while the general statement remains open.

Sources & referencesView supporting material

Primary source

Masataka Iwai, “On the structure of a log smooth pair in the equality case of the Bogomolov-Gieseker inequality”, arXiv:2103.08779 (2022).

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