On the slope and geography of fibred surfaces and threefolds

  1. Barja Yáñez, Miguel Ángel
Dirigée par:
  1. Juan Carlos Naranjo del Val Directeur/trice

Université de défendre: Universitat de Barcelona

Année de défendre: 1998

Jury:
  1. Juan Carlos Welters Dyadalewice President
  2. José Ignacio Burgos Gil Secrétaire
  3. Fabrizio Catanese Rapporteur
  4. Daniel Hernández Ruipérez Rapporteur
  5. Pere Pascual Gainza Rapporteur

Type: Thèses

Teseo: 69607 DIALNET lock_openTDX editor

Résumé

In this tesis we study numerical propieties of surfaces and threefolds, mainly fibred over curves, the so called "slope" of the fibration. We prove partially a conjecture of Fujita on the semiampleness of the direct image of the relative dualizing sheaf of a fibration. We give new lower bounds of the slope of a fibred surface depending on data of the general fibre (existence of involutions) and on data of the hole surface (the fibration not being the Albanese morphism, for example). We study the case of threefolds over curves. We prove that, in general, the relative algebraic Euler characteristic is nonnegative and give lower bound for the slope. We classify the lowest cases of the invariants.