English

Congruences like Atkin's for the partition function

Number Theory 2022-07-20 v2

Abstract

Let p(n)p(n) be the ordinary partition function. In the 1960s Atkin found a number of examples of congruences of the form p(Q3n+β)0(mod)p( Q^3 \ell n+\beta)\equiv0\pmod\ell where \ell and QQ are prime and 5315\leq \ell\leq 31; these lie in two natural families distinguished by the square class of 124β(mod)1-24\beta\pmod\ell. In recent decades much work has been done to understand congruences of the form p(Qmn+β)0(mod)p(Q^m\ell n+\beta)\equiv 0\pmod\ell. It is now known that there are many such congruences when m4m\geq 4, that such congruences are scarce (if they exist at all) when m=1,2m=1, 2, and that for m=0m=0 such congruences exist only when =5,7,11\ell=5, 7, 11. For congruences like Atkin's (when m=3m=3), more examples have been found for 5315\leq \ell\leq 31 but little else seems to be known. Here we use the theory of modular Galois representations to prove that for every prime 5\ell\geq 5, there are infinitely many congruences like Atkin's in the first natural family which he discovered and that for at least 17/2417/24 of the primes \ell there are infinitely many congruences in the second family.

Keywords

Cite

@article{arxiv.2112.09481,
  title  = {Congruences like Atkin's for the partition function},
  author = {Scott Ahlgren and Patrick B. Allen and Shiang Tang},
  journal= {arXiv preprint arXiv:2112.09481},
  year   = {2022}
}

Comments

Minor revisions to improve exposition

R2 v1 2026-06-24T08:21:54.553Z