English

Singularities on vertical $\epsilon$-log canonical Fano fibrations

Algebraic Geometry 2024-12-13 v1

Abstract

Given a Fano type log Calabi-Yau fibration (X,B)Z(X,B)\to Z with (X,B)(X,B) being ϵ\epsilon-lc, the first author in \cite{Bi23} proved that the generalised pair (Z,BZ+MZ)(Z,B_Z+M_Z) given by the canonical bundle formula is generalised δ\delta-lc where δ>0\delta>0 depends only on ϵ\epsilon and dimXdimZ\dim X-\dim Z, which confirmed a conjecture of Shokurov. In this paper, we prove the above result under a weaker assumption. Instead of requiring (X,B)(X,B) to be ϵ\epsilon-lc, we assume that (X,B)(X,B) is ϵ\epsilon-lc vertically over ZZ, that is, the log discrepancy of EE with respect to (X,B)(X,B) is ϵ\geq \epsilon for any prime divisor EE over XX whose center on XX is vertical over ZZ.

Keywords

Cite

@article{arxiv.2412.09382,
  title  = {Singularities on vertical $\epsilon$-log canonical Fano fibrations},
  author = {Caucher Birkar and Bingyi Chen},
  journal= {arXiv preprint arXiv:2412.09382},
  year   = {2024}
}

Comments

11 pages, comments welcome