You can use the ASINGULAR=, MSINGULAR=, and VSINGULAR= options to set three singularity criteria for the inversion of the Hessian matrix H. The singularity criterion used for the inversion is where ...

Further, the concept of phases in semi-sectorial matrices has been extended, providing a deeper understanding of matrix behavior in relation to eigenvalues and matrix sums. This work establishes ...

One significant area of research is the inverse eigenvalue problem of graphs, which investigates the conditions under which a given spectrum can be realized by a graph's adjacency matrix.