Dimensions of anisotropic indefinite quadratic forms II --- The lost proofs

Abstract

Let F be a field of characteristic different from 2. The u-invariant and the Hasse number of a field F are classical and important field invariants pertaining to quadratic forms. These invariants measure the suprema of dimensions of anisotropic forms over F that satisfy certain additional properties. We construct various examples of fields with infinite Hasse number and prescribed finite values of u that satisfy additional properties pertaining to the space of orderings of the field. We also construct to each positive integer n a real field F such such that the Hasse number is 2^{n+1} and such that each quadratic form over F of dimension 1+2^n is a Pfister neighbor. These results were announced (without proof) in the article "Dimensions of anisotropic indefinite quadratic forms II" by the present author.