Binary Symmetric Matrix Inversion Through Local Complementation

We consider the Schur complement operation for symmetric matrices over GF(2), which we identify with graphs through the adjacency matrix representation. It is known that Schur complementation for such a matrix (i.e., for a graph) can be decomposed into a sequence of two types of elementary Schur complement operations: (1) local complementation on a looped vertex followed by deletion of that vertex and (2) edge complementation on an edge without looped vertices followed by deletion of that edge. We characterize the symmetric matrices over GF(2) that can be transformed into the empty matrix using only operations of (1). As a consequence, we find that these matrices can be inverted using local complementation. The result is applied to the theory of gene assembly in ciliates.