Geometry of Numerical Range of Linear Operator Polynomial

Citation:

Deyu WU,Alatancang CHEN.Geometry of Numerical Range of Linear Operator Polynomial[J].Chinese Annals of Mathematics B,2025,46(1):151~162
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Authors:

Deyu WU; Alatancang CHEN

Foundation:

the National Natural Science Foundation of China (No. 11561048) and the Natural Science Foundation of Inner Mongolia (No. 2023MS01011).
Abstract: Let B(X) be the algebra of all bounded linear operators on a Hilbert space X. Consider an operator polynomial P(λ) = Amλm + Am?1λm?1 + · · · + A0, where Ai ∈ B(X), i = 0, 1, · · · , m. The numerical range of P(λ) is defined as W (P(λ)) = {λ ∈ C : (P(λ)x, x) = 0 for some x 6= 0}. The main goal of this paper is to respond to an open problem proposed by professor Li, and determine general conditions on connectivity, convexity and spectral inclusion property of W (P(λ)). They also consider the relationship between operator polynomial numerical range and block numerical range.

Keywords:

Linear operator polynomial  Numerical range  Connectedness  Convexity  Block numerical range

Classification:

47A12
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