Nullspace of a transpose incidence matrix

Recall the definition of the arc-node incidence matrix of a network.

By definition, the arc-node incidence matrix A, we have mathbf{1}^T A=  0, where mathbf{1} is the vector of ones (in mathbf{R}^m). Hence mathbf{1} is in the nullspace of A^T.

See also: Rank properties of the arc-node incidence matrix.