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arXiv 0807.5011math.RA
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*-环上的极大二次模

Maximal quadratic modules on *-rings

Jaka Cimpric

摘要:

本文将极大真二次模的概念和结果从交换单位环推广到$\ast$ -环,并讨论了这种推广与非交换实代数几何的最新发展的关系。极大真二次模的最简单例子是所有固定维数的半正定复矩阵的锥。证明了极大真二次模的支撑是素$\ast$ -理想的对称部分,Noether $\ast$ -环中的极大真二次模来自于带对合的简单Artin环中的极大真二次模,极大真二次模满足交定理.作为应用,我们得到了Schmudgen的严格正性定理对Weyl代数的如下推广:设$c$是Weyl代数$\mathcal{W}(d)$中在Schr odinger表示中不是半负定的元素.证明了在一定条件下,存在整数$k$和元素$r_1,...,r_k \in \mathcal{W}(d)$,使得$\sum_{j=1}^k r_j c r_j^\ast$是有限厄米平方和.然而,这个结果不是一个适当的推广,因为我们没有界$k \le d$。

英文摘要:

We generalize the notion of and results on maximal proper quadratic modules from commutative unital rings to $\ast$-rings and discuss the relation of this generalization to recent developments in noncommutative real algebraic geometry. The simplest example of a maximal proper quadratic module is the cone of all positive semidefinite complex matrices of a fixed dimension. We show that the support of a maximal proper quadratic module is the symmetric part of a prime $\ast$-ideal, that every maximal proper quadratic module in a Noetherian $\ast$-ring comes from a maximal proper quadratic module in a simple artinian ring with involution and that maximal proper quadratic modules satisfy an intersection theorem. As an application we obtain the following extension of Schm\" udgen's Strict Positivstellensatz for the Weyl algebra: Let $c$ be an element of the Weyl algebra $\mathcal{W}(d)$ which is not negative semidefinite in the Schr\" odinger representation. It is shown that under some conditions there exists an integer $k$ and elements $r_1,...,r_k \in \mathcal{W}(d)$ such that $\sum_{j=1}^k r_j c r_j^\ast$ is a finite sum of hermitian squares. This result is not a proper generalization however because we don't have the bound $k \le d$.

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