English

Effective birationality for sub-pairs with real coefficients

Algebraic Geometry 2020-07-06 v1

Abstract

For ϵ\epsilon-lc Fano type varieties XX of dimension dd and a given finite set Γ\Gamma, we show that there exists a positive integer m0m_0 which only depends on ϵ,d\epsilon,d and Γ\Gamma, such that both mKXimbiBi|-mK_X-\sum_i\lceil mb_i\rceil B_i| and mKXimbiBi|-mK_X-\sum_i\lfloor mb_i\rfloor B_i| define birational maps for any mm0m\ge m_0 provided that BiB_i are pseudo-effective Weil divisors, biΓb_i\in\Gamma, and (KX+ibiBi)-(K_X+\sum_ib_iB_i) is big. When Γ[0,1]\Gamma\subset[0,1] satisfies the DCC but is not finite, we construct an example to show that the effective birationality may fail even if XX is fixed, BiB_i are fixed prime divisors, and (X,B)(X,B) is ϵ\epsilon'-lc for some ϵ>0\epsilon'>0.

Cite

@article{arxiv.2007.01849,
  title  = {Effective birationality for sub-pairs with real coefficients},
  author = {Jingjun Han and Jihao Liu},
  journal= {arXiv preprint arXiv:2007.01849},
  year   = {2020}
}

Comments

21 pages, comments are welcome!

R2 v1 2026-06-23T16:50:19.129Z