Minimal Model Program with scaling and adjunction theory

TL;DR

This paper investigates the positivity of adjoint bundles in quasi polarized pairs using a Minimal Model Program with scaling, providing classification results for certain varieties based on genus and degree.

Contribution

It introduces a method to analyze the nefness of K_X + rL for high r via MMP with scaling and applies it to classify specific quasi polarized pairs and embedded varieties.

Findings

Classification of quasi polarized pairs with sectional genus 0 and 1.

Results on embedded varieties with degree less than 2 times codimension plus 2.

Insights into the positivity properties of adjoint bundles for high rational r.

Abstract

Let (X,L) be a quasi polarized pairs, i.e. X is a normal complex projective variety and L is a nef and big line bundle on it. We study, up to birational equivalence, the positivity (nefness) of the adjoint bundles K_X + rL for high rational number r. For this we run a Minimal Model Program with scaling relative to the divisor K_X +rL. We give some applications, namely the classification up to birational equivalence of quasi polarized pairs with sectional genus 0,1 and of embedded projective varieties X < P^N with degree smaller than 2codim(X) +2.