Generalized complexity conjecture for generalized log Calabi–Yau pairs

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Let (X,B,M.)(X,B,\mathbf M.) be a generalized log Calabi–Yau pair. Write ∣B∣|B| for the sum of the coefficients of BB and ∣M.∣|\mathbf M.| for the sum of the coefficients of the moduli part in its decomposition as a sum of nef Cartier divisors on a model where it descends.

Generalized complexity conjecture. The following statements hold:

dim⁡X+ρ(X)−∣B∣−∣M.∣≥0.\dim X+\rho(X)-|B|-|\mathbf M.|\geq 0.
  1. If equality holds, then (X,⌊B⌋)(X,\lfloor B\rfloor) is toric.
  2. If B=0B=0, M.\mathbf M. descends on XX, and equality holds, then XX is a product of projective spaces.

This conjecture interpolates between the complexity characterization of toric varieties and the Kobayashi–Ochiai theorem. The paper presents it as an open conjecture; in particular, the generalized klt case motivates the expected product-of-projective-spaces conclusion, while the corresponding generalized log canonical statement can fail.

References

Primary source

Yoshinori Gongyo and Joaquín Moraga, “Generalized complexity of surfaces”, arXiv:2301.08395 (2023).

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