The Artin-Springer Theorem for quadratic forms over semi-local rings with finite residue fields

Scully, Stephen

doi:10.1090/proc/13744

The Artin-Springer Theorem for quadratic forms over semi-local rings with finite residue fields
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Proc. Amer. Math. Soc. 146 (2018), 1-13 Request permission

Abstract:

Let $R$ be a commutative and unital semi-local ring in which 2 is invertible. In this note, we show that anisotropic quadratic spaces over $R$ remain anisotropic after base change to any odd-degree finite étale extension of $R$. This generalization of the classical Artin-Springer theorem (concerning the situation where $R$ is a field) was previously established in the case where all residue fields of $R$ are infinite by I. Panin and U. Rehmann. The more general result presented here permits one to extend a fundamental isotropy criterion of I. Panin and K. Pimenov for quadratic spaces over regular semi-local domains containing a field of characteristic $\neq 2$ to the case where the ring has at least one residue field which is finite.

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