Published online by Cambridge University Press: 20 November 2018
The Chowla conjecture states that if $t$ is any given positive integer, there are infinitely many prime positive integers
$N$ such that
$\text{Per}\left( \sqrt{N} \right)\,=\,t$, where
$\text{Per}\left( \sqrt{N} \right)$ is the period length of the continued fraction expansion for
$\sqrt{N}$. C. Friesen proved that, for any
$k\,\in \,\mathbb{N}$, there are infinitely many square-free integers
$N$, where the continued fraction expansion of
$\sqrt{N}$ has a fixed period. In this paper, we describe all polynomials
$Q\,\in \,{{\mathbb{F}}_{q}}\left[ X \right]$ for which the continued fraction expansion of
$\sqrt{Q}$ has a fixed period. We also give a lower bound of the number of monic, non-squares polynomials
$Q$ such that
$\deg \,Q=\,2d$ and
$Per\sqrt{Q}\,=\,t$.