I'm looking into the stability of a system of ODEs, for which we've mannaged to extract a Jacobian matrix. Two of our eigenvalues are within our nummerical error tolerance, but they are close to zero. One of them is positive, which poses a problem for our stability analysis. We do know that the rank of the matrix is 17, against the 19 variables we are studying (19x19 matrix). I'm guessing that this might imply that our two eigenvalues are in fact zeroes, but I'm having trouble putting anything more concrete down to paper. Do you guys know of any relationship between how many eigenvalues there are in zero and the nullity of the matrix?