Sos Approximations of Nonnegative Polynomials via Simple High Degree Perturbations
نویسنده
چکیده
We show that every real polynomial f nonnegative on [−1, 1]n can be approximated in the l1-norm of coefficients, by a sequence of polynomials {fεr} that are sums of squares. This complements the existence of s.o.s. approximations in the denseness result of Berg, Christensen and Ressel, as we provide a very simple and explicit approximation sequence. Then we show that if the moment problem holds for a basic closed semialgebraic set KS ⊂ Rn with nonempty interior, then every polynomial nonnegative on KS can be approximated in a similar fashion by elements from the corresponding preordering. Finally, we show that the degree of the perturbation in the approximating sequence depends on 2 as well as the degree and the size of coefficients of the nonnegative polynomial f , but not on the specific values of its coefficients.
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تاریخ انتشار 2006