Good Day scipy-dev members, Recently I have been working with the diagonalization routines of scipy, I am doing an study if the eigenvalues of a certain matrix, in particular I have interest in the differences between these eigenvalues. In order to do that I am doing the diagonalization process of each of the values of a parameter in a linespace, the diagonalization it has been carried out with the scipy.sparse.linalg.eigsh routine for few eigenvalues, however it seems to crash for negative values of the parameter. Why is this happening? In order to make my point more clear I have attached a plot of the difference between the first two eigenvalues. Thanks in advance, Manuel.