On mod p representations which are defined over Fp: II
Abstract
The behaviour of Hecke polynomials modulo p has been the subject of some study. In this note we show that, if p is a prime, the set of integers N such that the Hecke polynomials TN,l,k for all primes l, all weights k>1 and all characters taking values in +1,-1 splits completely modulo p has density 0, unconditionally for p=2 and under the Cohen-Lenstra heuristics for odd p. The method of proof is based on the construction of suitable dihedral modular forms.
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