English

Fano varieties with large pseudoindex and non-free rational curves

Algebraic Geometry 2024-06-04 v3 Complex Variables Differential Geometry

Abstract

For n4n\geq 4, let XX be a complex smooth Fano nn-fold whose minimal anticanonical degree of non-free rational curves on XX is at least n2n-2. We classify extremal contractions of such varieties. As an application, we obtain a classification of Fano fourfolds with pseudoindex and Picard number greater than one. Combining this result with previous results, we complete the classification of smooth Fano nn-folds with pseudoindex at least n2n-2 and Picard number greater than one. This can be seen as a generalization of various previous results. We also discuss the relations between pseudoindex and other invariants of Fano varieties.

Keywords

Cite

@article{arxiv.2309.03438,
  title  = {Fano varieties with large pseudoindex and non-free rational curves},
  author = {Kiwamu Watanabe},
  journal= {arXiv preprint arXiv:2309.03438},
  year   = {2024}
}

Comments

27 pages. I have combined previous versions of this paper and paper arXiv:2402.14283 into this one paper. The content has been significantly revised, including the title and introduction