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A Real Holomorphy Ring without the Schmüdgen Property

  Published:1999-09-01
 Printed: Sep 1999
  • Murray A. Marshall
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Abstract

A preordering $T$ is constructed in the polynomial ring $A = \R [t_1,t_2, \dots]$ (countably many variables) with the following two properties: (1)~~For each $f \in A$ there exists an integer $N$ such that $-N \le f(P) \le N$ holds for all $P \in \Sper_T(A)$. (2)~~For all $f \in A$, if $N+f, N-f \in T$ for some integer $N$, then $f \in \R$. This is in sharp contrast with the Schm\"udgen-W\"ormann result that for any preordering $T$ in a finitely generated $\R$-algebra $A$, if property~(1) holds, then for any $f \in A$, $f > 0$ on $\Sper_T(A) \Rightarrow f \in T$. Also, adjoining to $A$ the square roots of the generators of $T$ yields a larger ring $C$ with these same two properties but with $\Sigma C^2$ (the set of sums of squares) as the preordering.
MSC Classifications: 12D15, 14P10, 44A60 show english descriptions Fields related with sums of squares (formally real fields, Pythagorean fields, etc.) [See also 11Exx]
Semialgebraic sets and related spaces
Moment problems
12D15 - Fields related with sums of squares (formally real fields, Pythagorean fields, etc.) [See also 11Exx]
14P10 - Semialgebraic sets and related spaces
44A60 - Moment problems
 

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