Abstract
We consider the question what can be said about the rank of the Picard group Pic Xσ of a compact toric variety Xσ if we know only the combinatorial type of the associated fan σ. We establish upper and lower bounds for the rank of Pic Xσ and give conditions for Pic Xσ to be determined by the combinatorial type of σ. Furthermore, we show that for simple fans Pic Xσ is necessary isomorphic to {0} or Z and give an example for a compact toric variety having a trivial Picard group. Moreover in the projective case we study the relation between addition of T-invariant Cartier divisors on Xσ, taking tensor product of elements of Pic Xσ and piecewise linear functions on σ with Minkowski-addition of polytopes, where the latter operation is extended to a group operation. Finally, we explain the relation to strong cohomology in the projective case.
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Eikelberg, M. Picard Groups of compact toric Varieties and combinatorial Classes of Fans. Results. Math. 23, 251–293 (1993). https://doi.org/10.1007/BF03322301
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DOI: https://doi.org/10.1007/BF03322301