Low pole order frames on vertical jets of the universal hypersurface

TL;DR

This paper establishes explicit bounds for the generation of meromorphic frames on vertical jet spaces of universal hypersurfaces, advancing the understanding of hyperbolicity in complex algebraic geometry.

Contribution

It provides a concrete value for the constant c_n ensuring global generation of tangent bundles on jet spaces, refining previous theoretical results.

Findings

Explicit value c_n = (n^2 + 5n)/2 for global generation

Recovery of known constants for n=2 and n=3

Implications for degree estimates in hyperbolicity problems

Abstract

Of the two techniques introduced by Bloch, Green-Griffiths and developed by Siu, Demailly to establish Kobayashi hyperbolicity of generic high degree complex algebraic hypersurfaces X in P^(n+1), the second one, initiated by Clemens, Ein, Voisin and developed by Siu, Paun, Rousseau consists in constructing meromorphic frames on the space of the so-called vertical k-jets J_vert^k (X_univ) of the universal hypersurface X_univ parametrizing all X in P^(n+1) of degree d. In 2004, Siu announced that there exists a constant c_n such that the twisting of the tangent bundle to J_vert^n (X_univ) by O (c_n) is globally generated (frame property). The present article provides c_n = (n^2 + 5n) / 2, recovering c_2 = 7 (Paun), c_3 = 12 (Rousseau). Applications to effective degree estimates for algebraic degeneracy or hyperbolicity are expected, especially in dimension n = 4, granted that the Demailly-Semple algebra of jet polynomials invariant under reparametrization and under a certain unipotent action is, for n = k = 4, generated by 16 fundamental bi-invariants enjoying 41 groebnerized syzygies.