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MULTIQUADRATIC EXTENSIONS, RIGID FIELDS AND PYTHAGOREAN FIELDS
Published online by Cambridge University Press: 15 March 2002
Abstract
Let F be a field of characteristic other than 2. Let F(2) denote the compositum over F of all quadratic extensions of F, let F(3) denote the compositum over F(2) of all quadratic extensions of F(2) that are Galois over F, and let F{3} denote the compositum over F(2) of all quadratic extensions of F(2). This paper shows that F(3) = F{3} if and only if F is a rigid field, and that F(3) = K(3) for some extension K of F if and only if F is Pythagorean and K = F(√−1). The proofs depend mainly on the behavior of quadratic forms over quadratic extensions, and the corresponding norm maps.
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- © 2002 The London Mathematical Society
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