2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/70349Let $c$ be an element of the Weyl algebra $W(d)$ which is given by a strictly positive operator in the Schr"odinger representation. It is shown that, under some conditions, there exist elements $b_1,...,b_d$ in $W(d)$ such that $b_1 c b_1^* + ... + b_d c b_d^*$ is a finite sum of squares.17 pages, condition (i) in Theorem 1.1 implies (ii). Assumption (ii) can be omittedAlgebraic GeometryFunctional Analysis14P10; 14A22; 46K10text