Long's hypergeometric supercongruence conjecture

Let (r1,r2,q)(r_1,r_2,q) range over

{(12,12,43),(12,12,76),(12,13,76),(12,13,54),(12,14,76),(12,12,54)}.\left\{\left(\frac{1}{2},\frac{1}{2},\frac{4}{3}\right),\left(\frac{1}{2},\frac{1}{2},\frac{7}{6}\right),\left(\frac{1}{2},\frac{1}{3},\frac{7}{6}\right),\left(\frac{1}{2},\frac{1}{3},\frac{5}{4}\right),\left(\frac{1}{2},\frac{1}{4},\frac{7}{6}\right),\left(\frac{1}{2},\frac{1}{2},\frac{5}{4}\right)\right\}.

Set α(r1,r2)={r1,1r1,r2,1r2}\mathbf{\alpha}_{(r_1,r_2)}=\{r_1,1-r_1,r_2,1-r_2\} and βq={1,1,q,2q}\mathbf{\beta}_q=\{1,1,q,2-q\}. Let HD(r1,r2,q)\mathrm{HD}_{(r_1,r_2,q)} denote the hypergeometric datum (α(r1,r2),βq,1)(\mathbf{\alpha}_{(r_1,r_2)},\mathbf{\beta}_q,1). Long's conjecture. For each of these hypergeometric data, there exists an explicit weight 44 modular form f(r1,r2,q)f_{(r_1,r_2,q)} and Dirichlet character χ(r1,r2,q)\chi_{(r_1,r_2,q)} such that, for all primes p7p\geq 7,

p4F3[r11r1r21r21q2q;1]p1χ(r1,r2,q)(p)ap(f(r1,r2,q))(modp3).p\cdot {}_4F_3\left[\begin{matrix}r_1&1-r_1&r_2&1-r_2\\&1&q&2-q\end{matrix};1\right]_{p-1}\equiv \chi_{(r_1,r_2,q)}(p)a_p(f_{(r_1,r_2,q)})\pmod{p^3}.

The conjecture connects these hypergeometric supercongruences with modular forms. Modularity is known for the first three listed hypergeometric data, while the stated congruences and the required generalizations of Dwork's results remain to be established in full.

Sources & referencesView supporting material

Primary source

Michael Allen, “On Some Hypergeometric Supercongruence Conjectures of Long”, arXiv:2202.05408 (2022).

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