A solution to Fujita's freeness conjecture via an extension theorem with analytic adjoint ideal sheaves

TL;DR

This paper proves Fujita's freeness conjecture for ample line bundles on complex projective manifolds by employing an extension theorem with analytic adjoint ideal sheaves, offering a new approach to control singularities.

Contribution

It introduces a novel extension theorem utilizing analytic adjoint ideal sheaves to solve Fujita's conjecture, improving the understanding of lc singularities and their centers.

Findings

Proves Fujita's freeness conjecture for ample line bundles.

Develops an extension theorem based on injectivity techniques.

Provides a new method to handle lc singularities and centers.

Abstract

The effective freeness in Fujita's conjecture states that, for an ample line bundle $L$ on a complex projective manifold $X$, the adjoint bundle $K_X\otimes L^{\otimes m}$ is globally generated when $m \geq \dim_{\mathbb C} X + 1$. Following the approach of Angehrn and Siu, a solution is provided in this paper via the use of adjoint ideal sheaves, which provide a finer control of the non-integrable loci given by multiplier ideal sheaves, so that one can work directly with the lc singularities and the associated (minimal) lc centres as in the algebraic approaches of Kawamata and Helmke. The substitute for the Nadel or Kawamata-Viehweg vanishing theorem used in previous approaches is an extension theorem based on the techniques developed for the injectivity theorems.