Authors: Carla Fidalgo Alexander Kovacec
Publish Date: 2010/07/10
Volume: 269, Issue: 3-4, Pages: 629-645
Abstract
By a diagonal minus tail form of even degree we understand a real homogeneous polynomial Fx 1 x n = Fx = Dx − Tx where the diagonal part Dx is a sum of terms of the form b i x i2d with all b i ≥ 0 and the tail Tx a sum of terms a i 1i 2cdots i nx 1i 1cdots x ni n with a i 1i 2cdots i n 0 and at least two i ν ≥ 1 We show that an arbitrary change of the signs of the tail terms of a positive semidefinite diagonal minus tail form will result in a sum of squares of polynomials We also give an easily tested sufficient condition for a polynomial to be a sum of squares of polynomials sos and show that the class of polynomials passing this test is wider than the class passing Lasserre’s recent conditions Another sufficient condition for a polynomial to be sos like Lasserre’s piecewise linear in its coefficients is also given
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