Research Article
Inequalities Involving Essential Norm Estimates of
Product-Type Operators
Manisha Devi , Ajay K. Sharma, and Kuldip Raj
School of Mathematics, Shri Mata Vaishno Devi University, Katra 182320, Jammu and Kashmir, India
Correspondence should be addressed to Kuldip Raj; kuldipraj68@gmail.com
Received 11 September 2020; Revised 22 January 2021; Accepted 15 February 2021; Published 3 March 2021
Academic Editor: Ming-Sheng Liu
Copyright © 2021 Manisha Devi et al. is is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Consider an open unit disk D � z ∈ C: |z| < 1 { } in the complex plane C, ξ a holomorphic function on D,and ψ a holomorphic self-
map of D. For an analytic function f, the weighted composition operator is denoted and defined as follows:
(W
ξ,ψ
f)(z)� ξ(z)f(ψ(z)). We estimate the essential norm of this operator from Dirichlet-type spaces to Bers-type spaces and
Bloch-type spaces.
1. Introduction and Preliminaries
Consider an open unit disk D � z ∈ C: |z| < 1 { } in the
complex plane C. Let H(D) denote the class of all analytic
functions on D, S(D) be the class of all holomorphic self-
maps of D,and H
∞
be the space of all bounded holomorphic
functions on D. Let ξ ∈ H(D) and ψ be a holomorphic self-
map of D. For z ∈ D, the composition operator and mul-
tiplication operator are, respectively, defined by
C
ψ
f (z)� f(ψ(z)),
M
ξ
f (z)� ξ(z)f(z),
f ∈ H(D).
(1)
e weighted composition operator is denoted and
defined as
W
ξ,ψ
f (z)� ξ(z)f(ψ(z)), f ∈ H(D), (2)
where W
ξ,ψ
is a product-type operator as W
ξ,ψ
� M
ξ
C
ψ
.
Clearly, this operator can be seen as a generalization of the
composition operator and multiplication operator. It can be
easily seen that, for ξ ≡ 1, the operator reduced to C
ψ
. If
ψ(z)� z, the operator gets reduced to M
ξ
. is operator is
basically a linear transformation of H(D) defined by
(W
ξ,ψ
f)(z)� ξ(z)f(ψ(z)) � (M
ξ
C
ψ
f)(z), for f in H(D)
and z in D. e basic aim is to give the operator-theoretic
characterization of these operators in terms of function-
theoretic characterization of their including functions.
Various holomorphic function spaces on various domains
have been studied for the boundedness and compactness of
weighted composition operators acting on them. Moreover,
a number of papers have been studied on these operators
acting on different spaces of holomorphic functions on
various domains. For more details, see [1–14] and the ref-
erences therein. We say that a linear operator is bounded if
the image of a bounded set is a bounded set. Moreover, a
linear operator is said to be compact if it maps the bounded
sets to those sets whose closure is compact. For each α > 0,
the weighted Bloch space B is defined as follows:
B � f ∈ H(D): sup
z∈D
1 −|z|
2
α
f
′
(z)
<∞ . (3)
In this expression, seminormed is defined. is space
forms a Banach space with the natural norm defined by
‖f‖
B
�|f(0)| + sup
z∈D
1 −|z|
2
α
f
′
(z)
.
(4)
For α � 1, this space gets reduced to classical Bloch
space. A function ω: D ⟶(0, ∞) is said to be a weight if it
is continuous. For z ∈ D, the weight ω is said to be radial if
ω(z)� ω(|z|). A weight ω is said to be a standard weight if
Hindawi
Journal of Mathematics
Volume 2021, Article ID 8811309, 9 pages
https://doi.org/10.1155/2021/8811309