On Hilbert 17th problem and real nullstellensatz for global analytic functions



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Ruiz Sancho, Jesús María (1985) On Hilbert 17th problem and real nullstellensatz for global analytic functions. Mathematische Zeitschrift, 190 (3). pp. 447-454. ISSN 0025-5874

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The author proves a Nullstellensatz for the ring of real analytic functions on a compact analytic manifold. The main results are the following. Theorem 1: Let X be a compact irreducible analytic set of a real analytic manifold M and f:X→R a nonnegative analytic function. Then f is a sum of squares of meromorphic functions. Theorem 2: Let I be a finitely generated ideal of O(M) with Z(I) compact. Then IZ(I)=I√R, where Z(I) is the zero set of I, IZ(I) the ideal of functions (in O(M)) vanishing on I, and I√R the real radical of I (i.e. the set of functions f in O(M) such that there exist g1,⋯,gk and an integer p with f2p + g2 1 + ⋯ +g2k ∈ I). Corollary: Let I be as in Theorem 2. Then IZ(I)=I if and only if I is real (i.e. I=I √ R). The proofs are based on results about extension of orders.

Item Type:Article
Uncontrolled Keywords:Real nullstellensatz; Hilbert's 17th problem; sum of squares of; meromorphic functions; real radical
Subjects:Sciences > Mathematics > Algebraic geometry
Sciences > Mathematics > Set theory
ID Code:20069
Deposited On:21 Feb 2013 15:58
Last Modified:12 Dec 2018 15:14

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