Kohl's primitive-root permutation sign conjecture

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Let pp be an odd prime, let gg be a primitive root modulo pp, and define σg\sigma_g on Z/pZ={0,1,…,p−1}\mathbb Z/p\mathbb Z=\{0,1,\ldots,p-1\} by

σg(b):=gb\sigma_g(b):=g^b

for b∈{1,…,p−1}b\in\{1,\ldots,p-1\}, with σg(0)=0\sigma_g(0)=0. Let Rp\mathcal R_p be the set of primitive roots modulo pp, and regard σg\sigma_g as a permutation of Z/pZ\mathbb Z/p\mathbb Z. Kohl's conjecture. (i) If p≡1(mod4)p\equiv1\pmod4, then

#{g∈Rp:sgn⁡(σg)=1}=#{g∈Rp:sgn⁡(σg)=−1}.\#\{g\in\mathcal R_p:\operatorname{sgn}(\sigma_g)=1\}=\#\{g\in\mathcal R_p:\operatorname{sgn}(\sigma_g)=-1\}.

(ii) If p≡3(mod4)p\equiv3\pmod4, then for every g∈Rpg\in\mathcal R_p,

sgn⁡(σg)≡−(p−12)!(modp).\operatorname{sgn}(\sigma_g)\equiv-\left(\frac{p-1}{2}\right)!\pmod p.

The problem was posed by S. Kohl in 2018. The supplied status evidence says that this conjecture was confirmed by Ladisch and Petrov.

References

Primary source

Li-Yuan Wang and Hai-Liang Wu, “Applications of Lerch's theorem and permutations concerning quadratic residues”, arXiv:1810.03006 (2019).

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