2012/03/23 by Han, Lixing
#15A69 #65F15 #65K05 #FOS: Mathematics #Numerical Analysis (math.NA)
paper · doi:10.48550/arxiv.1203.5150
Let n be a positive integer and m be a positive even integer. Let \mathcal A be an mth order n-dimensional real weakly symmetric tensor and \mathcal B be a real weakly symmetric positive definite tensor of the same size. λ∈ R is called a \mathcal Br-eigenvalue of \mathcal A if \mathcal A xm-1 = λ\mathcal B xm-1 for some x ∈ Rn \backslash \0\. In this paper, we introduce two unconstrained optimization problems and obtain some variational characterizations for the minimum and maximum \mathcal Br--eigenvalues of \mathcal A. Our results extend Auchmuty's unconstrained variational principles for eigenvalues of real symmetric matrices. This unconstrained optimization approach can be used to find a Z-, H-, or D-eigenvalue of an even order weakly symmetric tensor. We provide some numerical results to illustrate the effectiveness of this approach for finding a Z-eigenvalue and for determining the positive semidefiniteness of an even order symmetric tensor.