The sRC quotient structure conjecture for klt pairs

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Let (X,Δ)(X,\Delta) be a klt pair with XX smooth and −(KX+Δ)-(K_X+\Delta) nef. An orbifold morphism is a morphism of pairs, and a pair is slope rationally connected when its general orbifold fibers have the corresponding slope rational connectedness property. Then there is an orbifold morphism

ρ:(X,Δ)⟶(R,ΔR)\rho:(X,\Delta)\longrightarrow(R,\Delta_R)

such that (R,ΔR)(R,\Delta_R) is a klt pair with RR smooth and c1(KR+ΔR)=0c_1(K_R+\Delta_R)=0, the general orbifold fibers (Xr,Δr)(X_r,\Delta_r) are slope rationally connected, and the fibration is locally trivial with respect to pairs: for every sufficiently small open set U⊂RU\subset R,

(ρ−1(U),Δ)≅(U,ΔR∣U)×(Xr,ΔXr),(\rho^{-1}(U),\Delta)\cong(U,\Delta_R|_U)\times(X_r,\Delta_{X_r}),

where XrX_r is a general fiber of ρ\rho.

sRC quotient structure conjecture. Such an orbifold morphism with all the stated properties exists.

The conjecture concerns a structure theorem for slope rationally connected quotients, which generalize MRC fibrations while incorporating the boundary. It was solved for log smooth surfaces, but remains open in general.

References

Primary source

Shin-ichi Matsumura, “Open problems on structure of positively curved projective varieties”, arXiv:2211.09153 (2022).

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