Bradley Delso, Margarita2023-06-202023-06-2019890764-4442https://hdl.handle.net/20.500.14352/57161Using some elementary theory of convex sets we prove a necessary and a sufficient condition for f ε R[x„ . . ., x„](R being the real numbers) to be a finite sum of 2m-th powers of rational functions in x1, . . ., x n over R[i.e.f ε ∑ R(x)2 m]engjournal articlerestricted access512.623.5511.55rench polynomial ringfunction fieldconvex setpositive semidefinite polynomialsum of 2m-th powersconvex hullsupporting hyperplaneTeoría de númerosÁlgebra1205 Teoría de Números1201 Álgebra