Seshadri constants of the anticanonical divisors of Fano manifolds with large index

[摘要] Seshadri constants, introduced by Demailly, measure the local positivity of a nef divisor at a point. In this paper, we compute the Seshadri constants of the anticanonical divisors of Fano manifolds with coindex at most 3 at a very general point. As a consequence, if Xis a nonsingular Fano threefold which is very general in its deformation family, then epsilon(X, -K-X; x) <= 1for all points x is an element of X if and only if vertical bar - K-X vertical bar is not base point free. (C) 2020 Elsevier B.V. All rights reserved.

[发布日期] 2020-12-01

[关键词] Seshadri constants;Anticanonical divisors;Fano manifolds;Rational curves;Fibration