Real Algebraic and Analytic Geometry |

Pure states, nonnegative polynomials and sums of squares.

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Submission: 2009, December 17.

*Abstract:
In recent years, much work has been devoted to a systematic study of polynomial identities
certifying strict or non-strict positivity of a polynomial on a basic closed semialgebraic set.
The interest in such identities originates not least from their importance in polynomial optimization.
The majority of the important results requires the archimedean condition, which implies
that the semialgebraic set has to be compact. This paper introduces the technique of pure states into commutative algebra.
We show that this technique allows an approach to most of the recent archimedean
Stellensätze that is considerably easier and more conceptual than the previous proofs.
In particular, we reprove and strengthen some of the most important results from the last years.
In addition, we establish several such results which are entirely new.
They are the first that allow the polynomial to have arbitrary, not necessarily discrete, zeros on the semialgebraic set.*

Mathematics Subject Classification (2000): 06F20, 11E25, 13J30, 06F25, 13A15, 14P10, 26C99, 46L30, 52A99.

Keywords and Phrases: pure states, extremal homomorphisms, order units, nonnegative polynomials, sums of squares, convex cones, quadratic modules, preorderings, semirings.

**Full text**, 26p.:
dvi 202k,
pdf 463k.

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