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arXiv · 1302.4722

Real Nullstellensatze and *-ideals in *-algebras

Jakob Cimpric·J. William Helton·Scott McCullough·Christopher Nelson
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Abstract

Let F denote either the real or complex field. An ideal I in the free *-algebra F in g freely noncommuting variables and their formal adjoints is a *-ideal if I = I*. When a real *-ideal has finite codimension, it satisfies a strong Nullstellensatz. Without the finite codimension assumption, there are examples of such ideals which do not satisfy, very liberally interpreted, any Nullstellensatz. A polynomial p in F is analytic if it is a polynomial in the variables {x} only; that is if p in F . As shown in this article, *-ideals generated by analytic polynomials do satisfy a natural Nullstellensatz and those generated by homogeneous analytic polynomials have a particularly simple description. The article also connects the results here for *-ideals to the literature on Nullstellensatz for left ideals in *-algebras generally and in F in particular. It also develops the concomitant general theory of *-ideals in general *-algebras.

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Jakob Cimpric, J. William Helton, Scott McCullough, Christopher Nelson. 2013-02-19. Real Nullstellensatze and *-ideals in *-algebras. https://doi.org/10.13001/1081-3810.2901

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