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LOCAL BORCHERDS PRODUCTS FOR UNITARY GROUPS

Published online by Cambridge University Press:  27 October 2017

ERIC HOFMANN*
Affiliation:
Mathematisches Institut, Universität Heidelberg, Im Neuenheimer Feld 205, D-69120 Heidelberg, Germany email hofmann@mathi.uni-heidelberg.de

Abstract

For the modular variety attached to an arithmetic subgroup of an indefinite unitary group of signature $(1,n+1)$, with $n\geqslant 1$, we study Heegner divisors in the local Picard group over a boundary component of a compactification. For this purpose, we introduce local Borcherds products. We obtain a precise criterion for local Heegner divisors to be torsion elements in the Picard group, and further, as an application, we show that the obstructions to a local Heegner divisor being a torsion element can be described by certain spaces of vector-valued elliptic cusp forms, transforming under a Weil representation.

Type
Article
Copyright
© 2017 Foundation Nagoya Mathematical Journal  

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