FACIAL STRUCTURES FOR SEPARABLE STATES
Hyun-Suk Choi, Seung-Hyeok Kye · Journal of the Korean Mathematical Society · 2012
The convex cone $\mathbb{V}_1$ generated by separable states is contained in the cone $\mathbb{T}$ of all positive semi-definite block matrices whose block transposes are also positive semi-definite. We characterize faces of the cone $\mathbb{V}_1$ induced by faces of the cone $\mathbb{T}$ which are determined by pairs of subspaces of matrices.