2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/225442It is shown that a trace invariant projection map, i.e. a positive unital idempotent map, of a finite dimensional C*-algebra into itself is non-decomposable if and only if it is atomic, or equivalently not the sum of a 2-positive and a 2-copositive map. In particular projections onto spin factors of dimension greater than 6 are atomic.7 pagesOperator Algebras46L05text