Chowla–Mordell theorem

In mathematics, the Chowla–Mordell theorem is a result in number theory determining cases where a Gauss sum is the square root of a prime number, multiplied by a root of unity. It was proved and published independently by Sarvadaman Chowla and Louis Mordell, around 1951.

In detail, if ${\displaystyle p}$ is a prime number, ${\displaystyle \chi }$ a nontrivial Dirichlet character modulo ${\displaystyle p}$, and

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