An extension of several essential numerical radius inequalities of 2 × 2 $2\times 2$ off-diagonal operator matrices

Abstract

Abstract In this work, we provide upper and lower bounds for the numerical radius of an n × n $n\times n$ off-diagonal operator matrix, which extends some results by Abu-Omar and Kittaneh (Stud. Math. 216:69–75, 2013; Linear Algebra Appl. 468:18–26, 2015; Rocky Mt. J. Math. 45(4):1055–1065, 2015), and Paul and Bag (Appl. Math. Comput. 222:2731–2943, 2013).

Keywords

• Numerical radius
• Off-diagonal part
• Operator matrix