upper and lower bounds for numerical radii of block shifts

Authors

p. y. wu

h.-l. gau

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.

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Journal title:
bulletin of the iranian mathematical society

Publisher: iranian mathematical society (ims)

ISSN 1017-060X

volume 41

issue Issue 7 (Special Issue) 2015

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