Title
Crouzeix's Conjecture Holds for Tridiagonal 3 x 3 Matrices with Elliptic Numerical Range Centered at an Eigenvalue.
Abstract
Crouzeix stated the following conjecture in [Integral Equations Operator Theory, 48 (2004), pp. 461-477]: For every n x n matrix A and every polynomial p, parallel to p(A)parallel to <= 2 max(z is an element of)W(A)vertical bar p(z)vertical bar, where W(A) is the numerical range of A. We show that the conjecture holds in its strong, completely bounded form, i.e., where p above is allowed to be any matrix-valued polynomial, for all tridiagonal 3 x 3 matrices with constant main diagonal, [GRAPHICS] , a, b(k), c(k) is an element of C, or equivalently, for all complex 3 x 3 matrices with elliptic numerical range and one eigenvalue at the center of the ellipse. We also extend the main result of Choi in [Linear Algebra Appl., 438 (2013), pp. 3247-3257] slightly.
Year
DOI
Venue
2018
10.1137/17M1110663
SIAM JOURNAL ON MATRIX ANALYSIS AND APPLICATIONS
Keywords
Field
DocType
Crouzeix's conjecture,3 x 3 matrix,elliptic numerical range
Tridiagonal matrix,Discrete mathematics,Polynomial,Matrix (mathematics),Mathematical analysis,Numerical range,Operator theory,Mathematics,Eigenvalues and eigenvectors,Bounded function,Main diagonal
Journal
Volume
Issue
ISSN
39
1
0895-4798
Citations 
PageRank 
References 
0
0.34
1
Authors
3
Name
Order
Citations
PageRank
Christer Glader111.30
Mikael Kurula211.71
Mikael Lindström310.96