Iterated Commutators for Multilinear Singular Integral Operators on Morrey Space with Non-Doubling Measures ()
1. Introduction
Let
be a positive Radon measures on
satisfying only the growth condition, that is, there exists a constant
and
such that
(1)
for any cube
with sides parallel to the coordinate axes.
will be the cube centered at x with side length
. For
, rQ will denote the cube with the same center as Q and with
. The set of all cubes
, satisfying
is denoted by
. In this note, we do not assume that
is doubling.
Nazarov, Treil and Volberg developed the theory of the singular integrals for the measures with growth condition to investigate the analytic capacity on the complex plane [1] [2]. Tolsa showed that the analytic capacity is subadditive and that it is bi-Lipschitz invariant [3] [4] and defined for the growth measures RBMO (regular bounded mean oscillation) space, the Hardy space
and the Littlewood-Paley decomposition [5] [6]. He also gave his
space in terms of the grand maximal operator [7]. Recently many people paid attention to the measure with growth condition because of recovering the Calderón-Zygmund theory and solving the long-standing open Painlevé problem.
The boundedness of fractional integral operators on the classical Morrey spaces was studied by Adams [8], Chiarenza et al. [9]. In [9], by establishing a pointwise estimate of fractional integrals in terms of the Hardy-Littlewood maximal function, they showed the boundedness of fractional integral operators on the Morrey spaces. In 2005, Sawano and Tanaka [10] gave a natural definition of Morrey spaces for Radon measures which might be non-doubling but satisfied the growth condition, and they investigated the boundedness in these spaces of some classical operators in harmonic analysis. Later on, Sawano [11] defined the generalized Morrey spaces on
for non-doubling measure and showed the properties of maximal operators, fractional integral operators and singular operators in this space.
A classical result of commutator is due to Coifman, Rochberg and Weiss [12], if
and T is a Calderón-Zygmund operator, then the commutator
is bounded on
spaces for
. The same result for the multilinear commutator was obtained by Pérez and Trujillo-Gonzalez [13]. Tolsa [5] developed the theory of Calderón-Zygmund operators and their commutators with RBMO functions in the setting of non-doubling measures. Hu, Meng and Yang [14] considered the multilinear commutator on Lebesgue spaces with non-doubling measures. Chen and Sawyer [15] modified the definition of RBMO to investigate the commutators of the potential operators and RBMO functions.
In the last decade, multilinear singular integrals of Calderón-Zygmund type have attracted great attentions. Some interesting results refer to [16] [17] [18] [19] [20] in the text of Lebesgue measures. It points out that Perez and Pradolini [21] introduced a said iterated commutators generated by the multilinear singular integral operators with Calderón-Zygmund type and vector function
and obtained the boundedness from
to
with
for
(in fact, they considered the weighted case). Xu [22] extended the result to the case of the non-doubling measures. Very recently, Tao and He [23] obtained the boundedness of the multilinear Calderón-Zygmund operators on the generalized Morrey spaces over the quasi-metric space of non-homogeneoustype. The aim of this paper is to study the iterated commutators of multilinear singular integral operators on Morrey spaces with non-doubling measures.
Before stating our result, we recall some definitions and notation. Given
large enough but depending only on the dimension d, we say that a cube
is doubling if
. For any fixed cube
, let N be the smallest nonnegative integer such that
is doubling. We denote this cube by
.
For two cubes
in
, we suppose
(2)
where
is the first positive integer k such that
. This was introduced by Tolsa in [5].
Let
be the mean value of f on Q, namely,
. The regularity bounded mean oscillations function spaces were introduced by Tolsa [5].
Definition 1.1. Let
be a fixed constant. We say that
is in RBMO if there exists a constant
such that
(3)
for any cube Q, and
(4)
for any two doubling cubes
. The mininal constant
is the
norm of f, and it will be denoted by
.
The definition of the Morrey space with non-doubling measure is given in the following [10].
Definition 1.2. Let
and
, the Morrey space
is defined as
where
(5)
It is easy to observe that
, and Hölder’s inequality tells us
for all
, then we have
. The space
is a Banach space with its norm
and the parameter
appearing in the definition does not affect it. The Morrey space norm reflects local regularity of f more precisely than the Lebesgue space norm. See [10] [11] [24] for details. We will denote
by
.
Denoting by
, we consider the multilinear singular integral operator
as follows,
(6)
whenever
are
-functions with compact support and
. Moreover,
(7)
and, for some
,
(8)
provided that
and
.
Let
for
and let
, then the iterated commutator
is formally defined as
(9)
Suppose
the main result in this paper can be stated as follow.
Theorem 1.1. Let
as in (9) and satisfying conditions (7) and (8). Let
with
and
. Suppose
for
. If
maps
to
, then the commutators
are bounded from
to
, that is,
(10)
More generally, denote by
the family of all subsets
of i different elements of
, and let
and
. For any
, we define
(11)
In case
, one sees that
is just the commutator
. So we have a more generalization version of the theorem as following.
Theorem 1.2. Let
as in (11) and satisfying conditions (7) and (8). Let
with
and
. Suppose
for
. If
maps
to
, then for all
, the commutators
are bounded from
to
, that is,
(12)
2. Proof of Main Results
Before proving our theorem, we recall the following maximal operator,
(13)
we will use the sharp maximal estimates. Let f be a function in
, the sharp maximal function of f is defined by
(14)
The non-centered doubling maximal operator is defined by
(15)
By the Lebesgue differential theorem, it is easy to see that
for any
and
. Define the non-centered maximal operator,
(16)
for
and
, where the supremum is taking over all the cubes Q containing the point x.
To prove Theorem 1.2 is reduced to the following lemmas.
Lemma 2.1. Let
and
and
. If
maps
to
and satisfying conditions (7) and (8). Then we have
(17)
We postpone the proof of Lemma 2.1 after of Theorem 1.2.
Lemma 2.2. [10] Let
, and
, then the operator
is bounded on
and
with the constant C independent of f.
Lemma 2.3. [24] Suppose that
, and there exists an increasing sequence of concentric doubling cubes,
, such that
Then there exist a constant
independent on f such that
Lemma 2.4. [25] Let
and
. If
maps
to
and satisfying conditions (7) and (8). Then there exists a constant C independent of
such that
Remark 2.1. If
maps
to
and satisfying conditions (7) and (8), with
,
and
. From Corollary 1.8 in [23], we can easily get that
is bounded from
to
.
Proof of Theorem 1.2. Using Lemma 2.1, Lemma 2.2, Lemma 2.3 and Lemma 2.4, we get that
Applying the inequality (17) in Lemma 2.1, for
, we have
where
and
are two nonempty subsets of
and
. Hence, we can make use of induction on
to get that
(18)
This completes the proof of Theorem 1.2.☐
For simplicity of the notation, we only show the special case
of Lemma 2.1. The similar process with minor modification will be to able prove Lemma 2.1 for the general case.
Lemma 2.5. Let
and
. If
maps
to
and satisfying conditions (7) and (8), then there exists a constant
independent of
and
such that
(19)
In order to prove Lemma 2.5, we have the following decomposition for the commutators
. For any
, writing
, thus it is clear that
. Moreover,
(20)
By expanding
and
hence we can obtain from the equality (20) that
(21)
where
are constants depending only on m and i.
Proof of Lemma 2.5. For simplicity, we denote by
the quantities on the right hand side of the inequality (19). Recall the definition of the sharp maximal operator
, and use the standard technique, see [15] for example, we only need to prove that
(22)
and
(23)
with the absolute constant C independent of
and R, where R is any doubling cube with
. In fact, we take
(24)
and clearly
(25)
Recall the equality (21), for any
, we have that
(26)
In order to show the inequality (22), we will calculate the integrals for the three functions above, respectively. Firstly, for
, by the Hölder inequality one sees that
(27)
where we have choose
such that
.
Similarly, for
, by the Hölder inequality, we also deduce that
(28)
To estimate the integral related to the function
, we split
as
, where
and
, this yields
(29)
where each term in
satisfies that
, for some
and some
. So we can decompose the function
further into three parts as follows
(30)
For
,we can take
such that
and
. Let
for each
, then
. Using Lemma 2.4, we know that the
is bounded from
to
. Hence, by this boundedness and Hölder inequality, we have
(31)
In order to estimate the integral of terms
and
over Q, we will give their point-wise estimates. In fact, for
, since
we observe that
(32)
where we have used the fact (see [5] ) that, there is an absolute constant C such that, for any
, integer
and cubes Q,
(33)
On the other hand, for
, we note for any
that
(34)
where we have use the inequation (33) again.
Taking the mean over
, we can obtain that
(35)
Combing the inequalities (26) (27), (28), (30), (31) and (33), we see from the estimates of
and
that the desired inequality (22) holds.
Next we turn to estimate the inequality (23). For any cubes
with
, where R is doubling. We denote
by N, then
and
. We recall the equality (29) and let
and
, and let
. Then we can write
(36)
For the term
, noting
(37)
and the similar argument as that for the estimate of
, we can obtain that
(38)
To estimate
, we recall the notations and note that, for any sequences
and
,
(39)
Using this equality and expanding
, we observe that
(40)
Similarly,
(41)
Thus
(42)
To estimate the integrals above, we recall that
and let
, then we can write that
and
, and thus we have
(43)
where
are constant independent of
and Q. From the equality (43), we can deduce that
(44)
where
and
Along the same lines as that of the pointwise estimates of
,we can obtain that, for
and if
,
(45)
Let
if
; and
thus for
,
Hence we get from (45) that, for
,
(46)
where we have used the fact that the cubes R and
are comparable, which implies
and
. Using the inequality (46) above and the identity (44), we obtain that, for
,
The estimates of
and
is very similar to the one used in the estimate of
. In fact, repeating the similar procedures used in (45) and (46) for
, and noting that
since
by the definition of N, we can deduce that
(47)
It is left to estimate the term in
of the case
. A small modification is needed to estimate this term. For
and
, one sees
This and the inequality (47) follows
Moreover, combing the estimates of
and
, we obtain the desired inequality (23).
Finally, let us show how to acquire the inequality (19) from the two inequalities (22) and (23). Fix the point x and let Q be any cube that
. notice
, hence we see from the inequalities (22) and (23) that
(48)
On the other hand for all doubling cubes
with
such that
, where
is the constant in Lemma 6 in [15], using (23), we have
(49)
and moreover the inequality (49) holds for any doubling cubes Q, R with
. Therefore,
(50)
According to the estimates (48) (50) and the definition of the sharp maximal function, we deduce the inequality (19) and so finish the proof of the Lemma 2.5.☐
3. Conclusions
The proof of Lemma 2.5 can be slightly modified to prove the conclusion of Lemma 2.1. Therefore we show that the iterated commutators generated by multilinear singular integrals operators
are bounded from
to
. Suppose
, the detailed conclusion can be described as follows: Let
as in (9) and satisfying conditions (7)
and (8). Let
with
and
. Suppose
for
. If
maps
to
, then the commutators
are bounded from
to
, that is,
More generally, let
as in (11) and satisfying conditions (7) and (8). Let
with
and
. Suppose
for
. If
maps
to
, then for all
, the commutators
are bounded from
to
, that is,
Funding
Supported by the National Natural Science Foundation of China (Grant No. 11161044 and Grant No. 11661061) and Natural science foundation of Inner Mongolia (No. 2019MS01003).