English

A Hecke algebra attached to mod 2 modular forms of level 3

Number Theory 2016-10-11 v2

Abstract

Let DD in Z/2[[x]]Z/2[[x]] be xn2\sum x^{n^{2}}, n>0n>0 and prime to 66. Let WW be spanned by the DkD^{k}, k>0k>0 and prime to 66. Then the formal Hecke operators TpT_{p}, p>3p>3, stabilize WW, and it can be shown that they act locally nilpotently. We show that the completion of the Hecke algebra generated by these TpT_{p} acting on WW, with respect to the maximal ideal generated by the TpT_{p}, is a power series ring in T7T_{7} and T13T_{13} with an element of square 00 adjoined. This may be viewed as a level 3 analog of the level 1 results of Nicolas and Serre -- the Hecke stable space they study is spanned by the odd powers of the mod 22 reduction of Δ\Delta, and their resulting completed Hecke algebra is a power series ring in T3T_{3} and T5T_{5}.

Keywords

Cite

@article{arxiv.1508.07523,
  title  = {A Hecke algebra attached to mod 2 modular forms of level 3},
  author = {Paul Monsky},
  journal= {arXiv preprint arXiv:1508.07523},
  year   = {2016}
}

Comments

Revised to include a sketch of a new simpler proof of the results of Nicolas and Serre in level 1. A reference to a result from arXiv 1604.02622 that completes our proof has been added. Typos have been corrected. 20 pages

R2 v1 2026-06-22T10:44:29.528Z