## Duke Mathematical Journal

### The signature of a toric variety

#### Abstract

We identify a combinatorial quantity (the alternating sum of the h-vector) defined for any simple polytope as the signature of a toric variety. This quantity was introduced by R. Charney and M. Davis in their work, which in particular showed that its nonnegativity is closely related to a conjecture of H. Hopf on the Euler characteristic of a nonpositively curved manifold.

We prove positive (or nonnegative) lower bounds for this quantity under geometric hypotheses on the polytope and, in particular, resolve a special case of their conjecture. These hypotheses lead to ampleness (or weaker conditions) for certain line bundles on toric divisors, and then the lower bounds follow from calculations using the Hirzebruch signature formula.

Moreover, we show that under these hypotheses on the polytope, the ith L-class of the corresponding toric variety is (−1)i times an effective class for any i.

#### Article information

Source
Duke Math. J., Volume 111, Number 2 (2002), 253-286.

Dates
First available in Project Euclid: 18 June 2004

https://projecteuclid.org/euclid.dmj/1087575041

Digital Object Identifier
doi:10.1215/S0012-7094-02-11123-5

Mathematical Reviews number (MathSciNet)
MR1882135

Zentralblatt MATH identifier
1062.14067

#### Citation

Leung, Naichung Conan; Reiner, Victor. The signature of a toric variety. Duke Math. J. 111 (2002), no. 2, 253--286. doi:10.1215/S0012-7094-02-11123-5. https://projecteuclid.org/euclid.dmj/1087575041

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