Problems / algebra
algebra / Birational geometry; Kodaira dimension
The Campana-Peternell conjecture on Kodaira dimension
Corollary 1.2: if m0KX−D is pseudo-effective for an effective Cartier (or, after clearing denominators, rational) divisor D on a smooth connected projective complex variety X, then κ(X)≥κ(D). Corollary 1.3: if f:X→Y is a fibre space and m0KX−f∗H is pseudo-effective with H ample, then κ(X)=κ(F)+dimY and ℓrKX−f∗H has sections for large ℓ (Schnell's general fibre-space conclusion). Both use canonical nonvanishing in every dimension from the family's abundance manuscript. The zero-Kodaira case of Schnell's question was already proved by Zou (2025) and is not new here.