Sum of two squares in cyclic quartic fields
Wenhuan Huang
Abstract
This paper gives an algorithm to determine whether a number in a cyclic quartic field is a sum of two squares, mainly based on local-global principle of isotropy of quadratic forms.
Wenhuan Huang
This paper gives an algorithm to determine whether a number in a cyclic quartic field is a sum of two squares, mainly based on local-global principle of isotropy of quadratic forms.
This paper contains 2 sections, 18 theorems, 14 equations.
Theorem 1
$K$ is a (real or imaginary) cyclic quartic extension of $\mathbb{Q}$, if and only if $K=\mathbb{Q}(\sqrt{A(D+B\sqrt{D})})=\mathbb{Q}(\sqrt{A(D-B\sqrt{D})})$, where $A$ is odd and square-free, $D=B^2+C^2$ is square-free, $B>0$, $C>0$, $(A,D)=1$.