Farmer–Gonek–Hughes conjecture on character sums

Let χ\chi be a primitive character modulo qq, and write τ=t+2\tau=|t|+2.

Farmer–Gonek–Hughes conjecture. As qq\to\infty, there is a constant BB such that

S(t,χ)(B+o(1))logqloglogq+O(logτ).|S(t,\chi)| \leq \bigl(B+o(1)\bigr)\sqrt{\log q\log\log q}+O(\log\tau).

The conjecture would substantially improve the currently admissible growth for S(t,χ)|S(t,\chi)| under GRH and could improve the paper's bounds for least character non-residues. The source attributes it to heuristics and predictions of Farmer, Gonek, and Hughes; it does not state that the conjecture has been proved.

Sources & referencesView supporting material

Primary source

Emanuel Carneiro, Micah B. Milinovich, Emily Quesada-Herrera and Antonio Pedro Ramos, “Fourier optimization, the least quadratic non-residue, and the least prime in an arithmetic progression”, arXiv:2404.08380 (2025).

Additional references

3 papers in this index state this conjecture (2019–2024). The statement above is taken from the most recent of them; the others are arXiv:1904.08204, arXiv:1902.02956.

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