Given a unital C*-algebra a *-closed subspace S containing 1 is called an operator system. One can associate to each subspace of a unital C*-algebra an operator system via .
The appropriate morphisms between operator systems are completely positive maps.
By a theorem of Choi and Effros, operator systems can be characterized as *-vector spaces equipped with an Archimedean matrix order.
Famous quotes containing the word system:
“Books are for the most part willfully and hastily written, as parts of a system to supply a want real or imagined.”
—Henry David Thoreau (1817–1862)