The sRC quotient structure conjecture for klt pairs

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 URU\subset R,

(ρ1(U),Δ)(U,ΔRU)×(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.

Sources & referencesView supporting material

Primary source

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

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