Hecke Eigenforms as Products of Eigenforms
Number Theory
2011-10-31 v1
Abstract
We investigate when the product of two Hecke eigenforms for {\Gamma}_1(N) is again a Hecke eigenform. In this paper we prove that the product of two normalized eigenforms for {\Gamma}_1(N), of weight greater than 1, is an eigenform only 61 times, and give a complete list. Duke [Duk99] and Ghate [Gha00] independently proved that with eigenforms for SL_2(Z), there are only 16 such product identities. Ghate [Gha02] also proved related results for {\Gamma}_1(N), with N square free. Emmons [Emm05] proved results for eigenforms away from the level, for prime level. The methods we use are elementary and effective, and do not rely on the Rankin-Selberg convolution method used by both Duke and Ghate.
Cite
@article{arxiv.1110.6430,
title = {Hecke Eigenforms as Products of Eigenforms},
author = {Matthew L. Johnson},
journal= {arXiv preprint arXiv:1110.6430},
year = {2011}
}
Comments
26 pages