1. Introduction
Throughout this article, s ( or ) is assumed to be an integer greater than or equal 2. Also, is assumed to be the unit sphere in the Euclidean space which is equipped with the normalized Lebesgue surface measure .
For fixed
, we define the mapping
by
with
. For a fixed
, the unique solution to the equation
is denoted by
. The metric space
is known by the mixed homogeneity space associated to
. Let
be the diagonal
matrix
The following transformation presents the change of variables concerning the space :
Hence,
, where
and
is the Jacobian of the transformation.
Fabes and Riviére showed in [
1] that
and that there is a constant
satisfying
For
, we assume that
where
h is a measurable function defined on
and ℧ is a measurable function defined on
which is integrable over
and satisfies the following properties:
and
For
, we define the generalized parabolic Marcinkiewicz integral
on product domains by
where
and
.
We notice that if
and
, then we have
,
,
,
, and
. In this case, we denote the operator
by
. In addition, when
,
and
, we denote
by
which is the classical Marcinkiewicz integral on product domains. The investigation of the boundedness of
began in [
2] in which the author proved the
boundedness of
under the condition
. Subsequently, the investigation of the
boundedness of
was considered by many authors (see for instance [
3,
4,
5,
6]).
On the other hand, the investigation of the
boundedness of the operator
was considered by many authors. For example, Al-Salman introduced
in [
7] in which he proved that
is bounded on
for all
provided that
. Later on, the authors of [
8] improved the results in [
7]. In fact, they proved the
boundedness of
for all
whenever ℧ in
with
or ℧ in
, and
with
. Here,
(for
) refers to the set of all measurable functions
h such that
Let us now recall the definition of Triebel-Lizorkin spaces on product domains. Let
and
. The homogeneous Triebel-Lizorkin space
is defined to be the set of all tempered distributions
g on
satisfying
where for
} and
,
and
is radial function satisfies the following:
(1) ,
(2) ,
(3) if for some constant A,
(4) with .
The authors of [
9] proved that the space
satisfies the following properties:
(i) For , we have ,
(ii) If , then ,
(iii) , where is the exponent conjugate to p,
(iv) The Schwartz space is dense in .
Recently, the authors of [
10] employed the extrapolation argument of Yano [
11] to prove that whenever
lies in the space
or in the space
, then for all
,
where
refers to a special class of block spaces introduced in [
12]. Very recently, the result in [
10] was improved in [
13] in which the authors proved that if
with
and
, then
is bounded on
for
with
and for
with
if
; and also for
with
and for
with
if
.
In the view of the results in [
8] regarding the boundedness of the parabolic Marcinkiewicz operator
and the results in [
13] regarding the boundedness of the generalized parametric Marcinkiewicz operator
, we have the following natural question: Is the integral operator
bounded under the same conditions on
h and ℧ that was assumed in [
13] ?
In this article, we shall answer the above question in the affirmative. In fact, we prove the following:
Theorem 1.
Let for some and for some . Then there exists a real number such that
for if , and for if ; where and is independent of
Theorem 2.
Let with and for some . Then
for all if and for all if .
By using the extrapolation argument in [
11,
14]) and the estimates in Theorems 1 - 2, we obtain the following results.
Theorem 3. Assume that h is given as in Theorem 1.
If with , then the inequality
holds for if , and for if .
If , then the inequality
holds for if , and for if .
Theorem 4. Suppose that with and with . Then the integral operator is bounded on for if , and for if .
(i) For the special case
and
, the authors of [
5] showed that
is bounded on
for all
under the condition
. Also, they found that this condition is the weakest possible condition so that the boundedness of
holds. On the other hand, the
(
) boundedness of
was proved in [
6] if
with
. Also, the optimality of the condition
is established. Therefore, the conditions on ℧ in Theorem 3 as well as Theorem 4 are the weakest known conditions in their respective classes for the case
and
.
(ii) In Theorem 4, when we consider the special case
, we get that
is bounded on
for all
if
, which improves the results in [
7,
10].
(iii) When with , Theorem 4 gives the boundedness of for all .
(iv) For the case
and
, the range of
p in Theorem 3 is better than the range obtained in Theorem 1.2 in [
8] in which the authors proved the
boundedness of
only for
.
(v) For
with
, our results are the same as that obtained in [
13].
Throughout the rest of the paper, the letter A stands for a positive constant which is independent of the essential variables and its value not necessary the same at each occurrence.