Asian Journal of Mathematics

Nef Reduction and Anticanonical Bundles

Thomas Bauer and Thomas Peternell

Abstract

Projective manifolds X with nef anticanonical bundles (i.e. - K X ∙ C = det T X ∙ C ≥ 0 for all curves C ⊂ X ) can be regarded as an interpolation between Fano manifolds (ample anticanonical bundle) and Calabi-Yau manifolds resp. tori and symplectic manifolds (trivial canonical bundle). A differential-geometric analogue are varieties with semi-positive Ricci curvature although this class is strictly smaller -- to get the correct picture one has to consider sequences of metrics and make the negative part smaller and smaller. However we will work completely in the context of algebraic geometry. Our aim is twofold: classification and, as a consequence, boundedness in case of dimension 3. We shall not consider threefolds with trivial canonical bundles, the eventual boundedness of Calabi-Yau threefolds still being unknown. Fano threefolds have been classified a long time ago and threefolds with big and nef anticanonical bundle are very much related with Q-Fano threefolds; therefore we will concentrate here on projective threefolds X with - KX nef and K3X = 0, but KX ≢ 0. The essential problem is to distinguish the positive and flat directions in X.

Article information

Source
Asian J. Math., Volume 8, Number 2 (2004), 315-352.

Dates
First available in Project Euclid: 24 June 2004

Permanent link to this document
https://projecteuclid.org/euclid.ajm/1088090064

Mathematical Reviews number (MathSciNet)
MR2129540

Zentralblatt MATH identifier
1078.14055

Citation

Bauer, Thomas; Peternell, Thomas. Nef Reduction and Anticanonical Bundles. Asian J. Math. 8 (2004), no. 2, 315--352. https://projecteuclid.org/euclid.ajm/1088090064


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