A local numerical range is analyzed for a family of circulant observables and states of composite 2 ⊗ d systems. It is shown that for any 2 ⊗ d circulant operator O there exists a basis giving rise to the matrix representation with real non-negative off-diagonal elements. In this basis the problem of finding extremum of O on product vectors |x ⊗ |y ∈ C 2 ⊗ C d reduces to the corresponding probl...

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...

abstract. the main contribution of the current paper is to propose a new effective numerical method for solving the first-order linear matrix differential equations. properties of the legendre basis operational matrix of integration together with a collocation method are applied to reduce the problem to a coupled linear matrix equations. afterwards, an iterative algorithm is examined for solvin...

We define the (convex) joint numerical range for an infinite family of compact operators in a Hilbert space H. use this set to determine whether self-adjoint operator A with ±‖A‖ its spectrum is minimal respect diagonals fixed basis E H norm, that ‖A‖≤‖A+D‖, all diagonal D. also describe moment mS=conv{|v|2:v∈S and ‖v‖=1} subspace S⊂H terms ranges obtain equivalences between intersection moment...

‎let $v$ be an $n$-dimensional complex inner product space‎. ‎suppose‎ ‎$h$ is a subgroup of the symmetric group of degree $m$‎, ‎and‎ ‎$chi‎ :‎hrightarrow mathbb{c} $ is an irreducible character (not‎ ‎necessarily linear)‎. ‎denote by $v_{chi}(h)$ the symmetry class‎ ‎of tensors associated with $h$ and $chi$‎. ‎let $k(t)in‎ (v_{chi}(h))$ be the operator induced by $tin‎ ‎text{end}(v)$‎. ‎the...

In this work, we define the joint normal eigenvalue, joint reducing approximate eigenvalue and we obtain some important and new results about the boundary of joint numerical range of n-tuple operators on a complex Hilbert space.

The numerical range of an n×n matrix polynomial P (λ) = Amλ + Am−1λm−1 + · · ·+ A1λ + A0 is defined by W (P ) = {λ ∈ C : x∗P (λ)x = 0, x ∈ C, x∗x = 1}, and plays an important role in the study of matrix polynomials. In this paper, we describe a methodology for the illustration of its boundary, ∂W (P ), using recent theoretical results on numerical ranges and algebraic curves.