We describe a fast algorithm to compute the real structured stability radius with respect to the open left-half plane or the open unit disk. It is based on a recent formula proved by Qiu et al. (Automatica, vol. 31, pp. 879-890, 1995) and the well-known correspondence between the singular values of a transfer function matrix and the imaginary eigenvalues of a related Hamiltonian matrix. Numeric...

The stability radius of a matrix polynomial P (λ) relative to an open region Ω of the complex plane and its relation to the numerical range of P (λ) are investigated. Using an expression of the stability radius in terms of λ on the boundary of Ω and ‖P (λ)−1‖2, a lower bound is obtained. This bound for the stability radius involves the distances of Ω to the connected components of the numerical...

Let ‎X be an ‎‎n-‎‎‎‎‎‎square complex matrix with the ‎Cartesian decomposition ‎‎X = A + i ‎B‎‎‎‎‎, ‎where ‎‎A ‎and ‎‎B ‎are ‎‎‎n ‎‎times n‎ ‎Hermitian ‎matrices. ‎It ‎is ‎known ‎that ‎‎$Vert X Vert_p^2 ‎leq 2(Vert A Vert_p^2 + Vert B Vert_p^2)‎‎‎$, ‎where ‎‎$‎p ‎‎geq 2‎$‎ ‎and ‎‎$‎‎Vert . Vert_p$ ‎is ‎the ‎Schatten ‎‎‎‎p-norm.‎ ‎‎ ‎‎In this paper‎, this inequality and some of its improvements ...

Abstract: The real decentralized fixed mode radius measures how “near” a decentralized LTI system is from having a decentralized fixed mode (DFM) present. In this paper, some properties of the real DFM radius are discussed, a procedure for computing the actual system parametric perturbations that achieve the real DFM radius is presented, and the real DFM radius is extended to deal with structur...

Denote the joint numerical radius of an m-tuple of bounded operators A = (A1, . . . , Am) by w(A). We give a complete description of maps f satisfying w(A − B) = w(f(A) − f(B)) for any two m-tuples of operators A = (A1, . . . , Am) and B = (B1, . . . , Bm). We also characterize linear isometries for the joint numerical radius, and maps preserving the joint numerical range of A. AMS Classificati...