Powers of Gauss sums in quadratic fields

Koji Momihara

Published 2020-11-30Version 1

In the past two decades, many researchers have studied {\it index $2$} Gauss sums, where the group generated by the characteristic $p$ of the underling finite field is of index $2$ in the unit group of ${\mathbb Z}/m{\mathbb Z}$ for the order $m$ of the associated multiplicative character of the filed. A complete solution to the problem of evaluating index $2$ Gauss sums was given by Yang and Xia~(2010). In particular, it is known that some nonzero integal powers of the Gauss sums in this case are in quadratic fields over the field of rational numbers. On the other hand, McEliece (1974), Evans (1981) and Aoki (2004, 2012) studied {\it pure} Gauss sums, some nonzero integral powers of which are in the field of rational numbers. In this paper, we study Gauss sums, some integral powers of which are in quadratic fields over the field of rational numbers. This class of Gauss sums is a generalization of index $2$ Gauss sums and an extension of pure Gauss sums to quadratic fields.