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A Real Holomorphy Ring without the Schmüdgen Property

Published online by Cambridge University Press:  20 November 2018

Murray A. Marshall*
Affiliation:
Department of Mathematics & Statistics University of Saskatchewan Saskatoon, SK S7N 0W0, email: [email protected]
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Abstract

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A preordering $T$ is constructed in the polynomial ring $A=\mathbb{R}[{{t}_{1}},{{t}_{2}},...]$ (countablymany variables) with the following two properties: (1) For each $f\,\in \,A$ there exists an integer $N$ such that $-\,N\,\le \,f\left( p \right)\,\le \,N$ holds for all $P\in \text{Spe}{{\text{r}}_{T}}(A)$. (2) For all $f\,\in \,A$, if $N+f,N-f\in T$ for some integer $N$, then $f\,\in \,\mathbb{R}$. This is in sharp contrast with the Schmüdgen-Wörmann result that for any preordering $T$ in a finitely generated $\mathbb{R}$-algebra $A$, if property (1) holds, then for any $f\in A,f>0\,\text{on}\,\text{Spe}{{\text{r}}_{T}}(A)\Rightarrow f\in T$. Also, adjoining to $A$ the square roots of the generators of $T$ yields a larger ring $C$ with these same two properties but with $\sum{{{C}^{2}}}$ (the set of sums of squares) as the preordering.

Keywords

Type
Research Article
Copyright
Copyright © Canadian Mathematical Society 1999

References

[1] Becker, E. and Powers, V., Sums of powers in rings and the real holomorphy ring. J. Reine Angew. Math. 480 (1996), 71103.Google Scholar
[2] Becker, E. and Schwartz, N., Zum Darstellungssatz von Kadison-Dubois. Arch. Math. 39 (1983), 421428.Google Scholar
[3] Bochnak, J., Coste, M. and Roy, M.-F., Géométrie Algébrique Réelle. Ergeb.Math. Grenzgeb., Springer, Berlin-Heidelberg-New York, 1987.Google Scholar
[4] Coste, M. and Roy, M.-F., La topologie du spectre réel. In: Ordered fields and real algebraic geometry, Contemp. Math. 8, Amer.Math. Soc., 1981, 27–59.Google Scholar
[5] Lam, T.-Y., An introduction to real algebra. Rocky Mtn. J. Math. 14 (1984), 767814.Google Scholar
[6] Monnier, J.-P., Schmüdgen Positivstellensatz. Manuscripta Math., to appearGoogle Scholar
[7] Schmüdgen, K., The K-moment problem for compact semi-algebraic sets. Math. Ann. 289 (1991), 203206.Google Scholar
[8] Wörmann, T., Strikt positive Polynome in der semialgebraischen Geometrie. PhD Thesis, Dortmund, 1998.Google Scholar