INTERVAL MATRICES - SINGULARITY AND REAL EIGENVALUES

This paper proves that a singular interval matrix contains a singular matrix of a very special form. This result is applied to study the real part L of the spectrum of an interval matrix. Under the assumption of sign stability of eigenvectors this paper gives a complete description of L by means of spectra of a finite subset of matrices and formulates a stability criterion for interval matrices with real eigenvalues that requires checking only two matrices for stability.