# Operator system

Given a unital C*-algebra $\mathcal{A}$, a *-closed subspace S containing 1 is called an operator system. One can associate to each subspace $\mathcal{M} \subseteq \mathcal{A}$ of a unital C*-algebra an operator system via $S:= \mathcal{M}+\mathcal{M}^* +\mathbb{C} 1$.