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Sharp maximal function inequalities and boundedness for Toeplitz type operator associated to singular integral operator with non-smooth kernel
Journal of Inequalities and Applications volume 2014, Article number: 141 (2014)
Abstract
In this paper, we establish the sharp maximal function inequalities for the Toeplitz type operator associated to some singular integral operator with non-smooth kernel. As an application, we obtain the boundedness of the operator on Morrey and Triebel-Lizorkin spaces.
MSC:42B20, 42B25.
1 Introduction and preliminaries
As the development of the singular integral operators, their commutators and multilinear operators have been well studied (see [1–3]). In [1, 2], the authors prove that the commutators generated by the singular integral operators and BMO functions are bounded on for . Chanillo (see [4]) proves a similar result when singular integral operators are replaced by the fractional integral operators. In [5, 6], the boundedness for the commutators generated by the singular integral operators and Lipschitz functions on Triebel-Lizorkin and () spaces are obtained. In [7–9], some Toeplitz type operators associated to the singular integral operators and strongly singular integral operators are introduced, and the boundedness for the operators generated by BMO and Lipschitz functions are obtained. In [10, 11], some singular integral operators with non-smooth kernel are introduced, and the boundedness for the operators and their commutators are obtained (see [9, 12–16]). The main purpose of this paper is to study the Toeplitz type operator generated by the singular integral operator with non-smooth kernel and the Lipschitz and BMO functions.
Definition 1 A family of operators , is said to be an ‘approximation to the identity’ if, for every , can be represented by a kernel in the following sense:
for every with , and satisfies
where ρ is a positive, bounded, and decreasing function satisfying
for some .
Definition 2 A linear operator T is called a singular integral operator with non-smooth kernel if T is bounded on and associated with a kernel such that
for every continuous function f with compact support, and for almost all x not in the support of f.
-
(1)
There exists an ‘approximation to the identity’ such that has the associated kernel and there exist so that
-
(2)
There exists an ‘approximation to the identity’ such that has the associated kernel which satisfies
and
for some , .
Let b be a locally integrable function on and T be the singular integral operator with non-smooth kernel. The Toeplitz type operator associated to T is defined by
where are the singular integral operator with non-smooth kernel T or ±I (the identity operator), and are the linear operators, , , and is the fractional integral operator () (see [4]).
Note that the commutator is a particular operator of the Toeplitz type operator . The Toeplitz type operator is the non-trivial generalizations of the commutator. It is well known that commutators are of great interest in harmonic analysis and have been widely studied by many authors (see [2]). In [10, 11], the boundedness of the singular integral operator with non-smooth kernel are obtained. In [12–16], the boundedness of the commutator associated to the singular integral operator with non-smooth kernel are obtained. Our works is motivated by these papers. In this paper, we will prove the sharp maximal inequalities for the Toeplitz type operator . As the application, we obtain the Morrey and Triebel-Lizorkin spaces boundedness for the Toeplitz type operator .
Definition 3 Let and . The Triebel-Lizorkin space associated with the ‘approximations to the identity’ is defined by
where
and the supremum is taken over all cubes Q of with sides parallel to the axes, and denotes the side length of Q.
Now, let us introduce some notations. Throughout this paper, will denote a cube of with sides parallel to the axes and center at x and edge is r. For any locally integrable function f, the sharp function of f is defined by
where, and in what follows . It is well known that (see [3])
and
We say that f belongs to if belongs to and .
Let M be the Hardy-Littlewood maximal operator defined by
For , let .
For and , set
The weight is defined by (see [17])
The sharp maximal function associated with the ‘approximation to the identity’ is defined by
where and denotes the side length of Q.
For , the Lipschitz space is the space of functions f such that
Throughout this paper, φ will denote a positive, increasing function on for which there exists a constant such that
Let f be a locally integrable function on . Set, for and ,
The generalized fractional Morrey spaces are defined by
We write if , which is the generalized Morrey space. If , , then , which is the classical Morrey space (see [18, 19]). As the Morrey space may be considered as an extension of the Lebesgue space (the Morrey space becomes the Lebesgue space when ), it is natural and important to study the boundedness of the operator on the Morrey spaces with (see [20–23]). The purpose of this paper is twofold. First, we establish some sharp inequalities for the Toeplitz type operator , and, second, we prove the boundedness for the Toeplitz type operator by using the sharp inequalities.
2 Theorems and lemmas
We shall prove the following theorems.
Theorem 1 Let T be the singular integral operator with non-smooth kernel as Definition 2, , and . If for any (), then there exists a constant such that, for any and ,
Theorem 2 Let T be the singular integral operator with non-smooth kernel as Definition 2, , and . If for any (), then there exists a constant such that, for any and ,
Theorem 3 Let T be the singular integral operator with non-smooth kernel as Definition 2, and . If for any (), then there exists a constant such that, for any and ,
Theorem 4 Let T be the singular integral operator with non-smooth kernel as Definition 2, , , , and . If for any () and and are the bounded operators on for , , then is bounded from to .
Theorem 5 Let T be the singular integral operator with non-smooth kernel as Definition 2, , , and . If for any () and and are the bounded operators on for , , then is bounded from to .
Theorem 6 Let T be the singular integral operator with non-smooth kernel as Definition 2, , , and . If for any () and and are the bounded operators on for , , then is bounded from to .
Corollary 1 Let be the commutator generated by the singular integral operator T with non-smooth kernel and b. Then Theorems 1-6 hold for .
To prove the theorems, we need the following lemmas.
Let T be the singular integral operator with non-smooth kernel as Definition 2. Then, for every , ,
Let be an ‘approximation to the identity’. For any , there exists a constant independent of γ such that
for , where D is a fixed constant which only depends on n. Thus, for , and ,
Lemma 3 (See [14])
Let be an ‘approximation to the identity’ and be the kernel of difference operator . Then
Suppose that , , and . Then
and
Lemma 5 Let be an ‘approximation to the identity’ and . Then
-
(a)
for ;
-
(b)
for , and ;
-
(c)
for , and .
Proof (a) For any cube in , we know for any cube by [24]. Noticing that and if , by Lemma 2, we have
thus
The proofs of (b) and (c) are similar to that of (a) by Lemma 4, we omit the details. □
3 Proofs of theorems
Proof of Theorem 1 It suffices to prove for , the following inequality holds:
where and denotes the side length of Q. Without loss of generality, we may assume are T (). Fix a cube and . We write, by ,
where
and
Then
Now, let us estimate , , , , , and , respectively. For , by Hölder’s inequality and Lemma 1, we obtain
thus
For , by Lemma 4, we obtain, for ,
For , by the condition on and notice for , , then , we obtain, similar to the proof of ,
thus
Similarly, by Lemma 4, for ,
For , we get, for ,
thus
Similarly, by Lemma 3, we get
These complete the proof of Theorem 1. □
Proof of Theorem 2 It suffices to prove for , the following inequality holds:
where and denotes the side length of Q. Without loss of generality, we may assume are T (). Fix a cube and . Similar to the proof of Theorem 1, we have
By using the same argument as in the proof of Theorem 1, we get
These complete the proof of Theorem 2. □
Proof of Theorem 3 It suffices to prove for , the following inequality holds:
where and denotes the side length of Q. Without loss of generality, we may assume are T (). Fix a cube and . Similar to the proof of Theorem 1, we have
Now, let us estimate , , , , and , respectively. For , we obtain, for ,
For , we obtain, for and ,
For , by for , , we obtain, for ,
Similarly, for , and , we get
These complete the proof of Theorem 3. □
Proof of Theorem 4 Choose in Theorem 1 and set . We have, by Lemma 5,
This completes the proof of the theorem. □
Proof of Theorem 5 Choose in Theorem 2. We have, by Lemma 4,
This completes the proof of the theorem. □
Proof of Theorem 6 Choose in Theorem 3, we have, by Lemma 5,
This completes the proof of the theorem. □
4 Applications
In this section we shall apply Theorems 1-6 of the paper to the holomorphic functional calculus of linear elliptic operators. First, we review some definitions regarding the holomorphic functional calculus (see [10, 11]). Given . Define
and its interior by . Set . A closed operator L on some Banach space E is said to be of type θ if its spectrum and for every , there exists a constant such that
For , let
where . Set
If L is of type θ and , we define by
where Γ is the contour parameterized clockwise around with . If, in addition, L is one-one and has dense range, then, for ,
where . L is said to have a bounded holomorphic functional calculus on the sector , if
for some and for all .
Now, let L be a linear operator on with so that generates a holomorphic semigroup , . Applying Theorem 6 of [11] and Theorems 1-6, we get
Corollary 2 Assume the following conditions are satisfied:
-
(i)
The holomorphic semigroup , is represented by the kernels which satisfy, for all , an upper bound
for , and , where and s is a positive, bounded, and decreasing function satisfying
-
(ii)
The operator L has a bounded holomorphic functional calculus in , that is, for all and , the operator satisfies
Let be the Toeplitz type operator associated to . Then Theorems 1-6 hold for .
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Zhou, X. Sharp maximal function inequalities and boundedness for Toeplitz type operator associated to singular integral operator with non-smooth kernel. J Inequal Appl 2014, 141 (2014). https://doi.org/10.1186/1029-242X-2014-141
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DOI: https://doi.org/10.1186/1029-242X-2014-141