Positive semidefinite rank

Abstract

Let M∈R[superscript p×q] be a nonnegative matrix. The positive semidefinite rank (psd rank) of M is the smallest integer k for which there exist positive semidefinite matrices A[subscript i],B[subscript j] of size k×k such that M[subscript ij]=trace(A[subscript i]B[subscript j]). The psd rank has many appealing geometric interpretations, including semidefinite representations of polyhedra and information-theoretic applications. In this paper we develop and survey the main mathematical properties of psd rank, including its geometry, relationships with other rank notions, and computational and algorithmic aspects.