Real Nullstellensatze and *-ideals in *-algebras
Abstract
Let F denote either the real or complex field. An ideal I in the free *-algebra F<x,x*> 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<x,x*> is analytic if it is a polynomial in the variables {x} only; that is if p in F<x>. 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<x,x*> in particular. It also develops the concomitant general theory of *-ideals in general *-algebras.
Keywords
Cite
@article{arxiv.1302.4722,
title = {Real Nullstellensatze and *-ideals in *-algebras},
author = {Jakob Cimpric and J. William Helton and Scott McCullough and Christopher Nelson},
journal= {arXiv preprint arXiv:1302.4722},
year = {2018}
}