German University of Technology in Oman, Way no. 36, Building no. 331, North Ghubrah, Muscat, Oman
Copyright © 2010 Bernhard Heim. This is an open access article distributed under the
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Let be the space of Siegel modular forms of degree and even weight . In this paper firstly a certain subspace Spez the Spezialschar of , is introduced. In the setting of the Siegel threefold, it is proven that this Spezialschar is the Maass Spezialschar. Secondly, an embedding of into a direct sum
Sym2 is given. This leads to a basic characterization of the Spezialschar property. The
results of this paper are directly related to the nonvanishing of certain
special values of L-functions related to the Gross-Prasad conjecture. This
is illustrated by a significant example in the paper.