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BY 4.0 license Open Access Published by De Gruyter Open Access April 1, 2019

Berezin number inequalities for operators

  • Mojtaba Bakherad and Mubariz T. Garayev EMAIL logo
From the journal Concrete Operators

Abstract

The Berezin transform à of an operator A, acting on the reproducing kernel Hilbert space ℋ = ℋ (Ω) over some (non-empty) set Ω, is defined by Ã(λ) = 〉Aǩ λ, ǩ λ〈 (λ ∈ Ω), where kλ=kλkλ is the normalized reproducing kernel of ℋ. The Berezin number of an operator A is defined by ber(A)=supλΩ|A˜(λ)|=supλΩ|Akλ,kλ|. In this paper, we prove some Berezin number inequalities. Among other inequalities, it is shown that if A, B, X are bounded linear operators on a Hilbert space ℋ, then

ber(AX±XA)ber12(A*A+AA*)ber12(X*X+XX*)

and

ber2(A*XB)X2ber(A*A)ber(B*B).

We also prove the multiplicative inequality

ber(AB)ber(A)ber(B)

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Received: 2018-04-05
Accepted: 2019-02-05
Published Online: 2019-04-01

© 2019 Mojtaba Bakherad et al., published by De Gruyter

This work is licensed under the Creative Commons Attribution 4.0 Public License.

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