Bulletin of the Iranian Mathematical Society

Bulletin of the Iranian Mathematical Society

Upper and lower bounds for numerical radii of block shifts

Authors
1 Department of Applied Mathematics, National Chiao Tung University, Hsinchu 30010, Taiwan.
2 Department of Mathematics, National Central University, Chun-gli 32001, Taiwan.
Abstract
For an n-by-n complex matrix A in a block form with the (possibly) nonzero blocks only on the diagonal above the main one, we consider two other matrices whose nonzero entries are along the diagonal above the main one and consist of the norms or minimum moduli of the diagonal blocks of A. In this paper, we obtain two inequalities relating the numeical radii of these matrices and also determine when either of them becomes an equality.
Keywords
Subjects

Volume 41, Issue 7 (Special Issue)
December 2015
Pages 15-27

  • Receive Date 04 September 2014
  • Revise Date 02 December 2014
  • Accept Date 02 December 2014