The moduli-part freeness conjecture

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Let f:X→Yf:X\to Y be a contraction of normal varieties and let KX+BK_X+B be a log divisor such that

  • KX+B∼Q,f0K_X+B\sim_{\mathbb{Q},f}0;
  • KX+BK_X+B is Kawamata log terminal over ηY\eta_Y;
  • (X,B)(X,B) has log nonsingular support and OY,ηY=(f∗OX(⌈−B⌉))ηY\mathcal O_{Y,\eta_Y}=(f_*\mathcal O_X(\lceil-B\rceil))_{\eta_Y}.

Positivity conjecture. Then KY+BYK_Y+B_Y is Q\mathbb{Q}-Cartier and the moduli part MYM_Y is Q\mathbb{Q}-free: for some ν∈N\nu\in\mathbb{N}, OY(νMY)\mathcal O_Y(\nu M_Y) is generated by global sections. This is the anticipated positivity statement for the moduli part in the canonical bundle formula, strengthening nefness to freeness. The source attributes the expectation to Kawamata and Mori; the supplied text gives no resolution status.

References

Primary source

Florin Ambro, “The Adjunction Conjecture and its applications”, arXiv:math/9903060 (1999).

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