No abstract

A classical observation of Deligne shows that, for any prime p ≥ 5 p \geq 5 , the divisor polynomial of the Eisenstein series E p − 1 ( z ) E_{p-1}(z) mod p p is closely related to the supersingular polynomial at p p , S p ( x ) ≔ ∏ E / F ¯ p  supersingular ( x − j ( E ) ) ∈ F p [ x ] . \begin{align*} S_p(x) ≔\prod _{E/\overline {\mathbb {F}}_p \text { supersingular}}(x-j(E))\,\, \in \mathbb {F}_p[x]. \end{align*} Deuring, Hasse, and Kaneko and Zagier [Supersingular j-invariants, hypergeometric series, and Atkin’s orthogonal polynomials, Providence, RI, 1998, pp. 97–126] found other families of modular forms which also give the supersingular polynomial at p p . In a new approach, we prove an analogue of Deligne’s result for the Hecke trace forms T k ( z ) T_k(z) defined by the Hecke action on the space of cusp forms S k S_k . We use the Eichler-Selberg trace formula to identify congruences between trace forms of different weights mod p p , and then relate their divisor polynomials to S p ( x ) S_p(x) using Deligne’s observation.

No abstract

We compute effective bounds for α(n), the Fourier coefficients of Ramunujan's mock theta function f (q) utilizing a finite algebraic formula due to Bruinier and Schwagenscheidt. We then use these bounds to prove two conjectures of Hou and Jagadeesan on the convexity and maximal multiplicative properties of the even and odd partition rank counting functions.

A number of recent papers have estimated ratios of the partition function $p(n-j)/p(n)$ , which appear in many applications. Here, we prove an easy-to-use effective bound on these ratios. Using this, we then study the second shifted difference of partitions, $f(\,j,n) := p(n) -2p(n-j) +p(n-2j)$ , and give another easy-to-use estimate of $f(\,j,n)$ . As applications of these, we prove a shifted convexity property of $p(n)$ , as well as giving new estimates of the k-rank partition function $N_k(m,n)$ and non-k-ary partitions along with their differences.