Abstract
The main object of the present paper is a numerical criterion determining when a Weil divisor of a \({\mathbb {Q}}\)–factorial complete toric variety admits a positive multiple Cartier divisor which is either numerically effective (nef) or ample. It is a consequence of \({\mathbb {Z}}\)–linear interpretation of Gale duality and secondary fan as developed in several previous papers of us. As a byproduct we get a computation of the Cartier index of a Weil divisor and a numerical characterization of weak \({\mathbb {Q}}\)–Fano, \({\mathbb {Q}}\)–Fano, Gorenstein, weak Fano and Fano toric varieties. Several examples are then given and studied.
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The authors were partially supported by the MIUR-PRIN 2010–2011 Research Funds “Geometria delle Varietà Algebriche”. The first author is also supported by the I.N.D.A.M. as a member of the G.N.S.A.G.A.
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Rossi, M., Terracini, L. A numerical ampleness criterion via Gale duality. AAECC 28, 351–368 (2017). https://doi.org/10.1007/s00200-016-0308-5
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DOI: https://doi.org/10.1007/s00200-016-0308-5
Keywords
- \({\mathbb {Q}}\)–factorial complete toric variety
- Ample divisor
- Nef divisor
- \({\mathbb {Z}}\)-liner Gale duality
- Secondary fan
- Ampleness criterion
- Cartier index
- \({\mathbb {Q}}\)-Fano toric variety