On the Binary Rank of Matrices with Constant Real Rank
This study addresses the longstanding open problem in combinatorial optimization concerning upper bounds on the binary rank of matrices with fixed real rank, which has previously relied on computer-assisted verification without a general theoretical framework. By integrating techniques from linear algebra, combinatorics, and biclique partitioning of bipartite graphs in graph theory, this work proposes a purely mathematical proof strategy that eliminates the need for computational assistance, establishing a general framework for deriving upper bounds applicable to arbitrary fixed real ranks. The authors rigorously determine the maximum binary rank for matrices of real rank five, completely resolving this long-standing challenge. Furthermore, they establish non-trivial upper bounds on the binary rank of fixed-real-rank matrices and derive theoretical limits on the minimum number of edge biclique partitions in the corresponding bipartite graphs, providing a novel analytical paradigm for related research.