On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces

UDC 517.5 In the framework of variable exponent Morrey and Morrey–Herz spaces, we prove some boundedness results for the commutator of Marcinkiewicz integrals with rough kernels. The approach is based on the theory of variable exponent and on generalization of the BMO-norms.

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Дата:2020
Автори: Qu, M., Wang, L.
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Мова:Англійська
Опубліковано: Institute of Mathematics, NAS of Ukraine 2020
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Назва журналу:Ukrains’kyi Matematychnyi Zhurnal
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Ukrains’kyi Matematychnyi Zhurnal
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author Qu, M.
Wang, L.
Qu, M.
Wang, L.
author_facet Qu, M.
Wang, L.
Qu, M.
Wang, L.
author_sort Qu, M.
baseUrl_str https://umj.imath.kiev.ua/index.php/umj/oai
collection OJS
datestamp_date 2022-03-26T11:01:57Z
description UDC 517.5 In the framework of variable exponent Morrey and Morrey–Herz spaces, we prove some boundedness results for the commutator of Marcinkiewicz integrals with rough kernels. The approach is based on the theory of variable exponent and on generalization of the BMO-norms.
doi_str_mv 10.37863/umzh.v72i7.6023
first_indexed 2026-03-24T03:25:22Z
format Article
fulltext DOI: 10.37863/umzh.v72i7.6023 UDC 517.5 M. Qu (School Math. and Statistics, Anhui Normal Univ., Wuhu, China), L. Wang (School Math. and Phys., Anhui Polytech. Univ., Wuhu, China) ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS IN VARIABLE MORREY TYPE SPACES* ПРО КОМУТАТОР IНТЕГРАЛIВ МАРЦИНКЕВИЧА З ГРУБИМИ ЯДРАМИ У ЗМIННИХ ПРОСТОРАХ ТИПУ МОРРЕЯ In the framework of variable exponent Morrey and Morrey – Herz spaces, we prove some boundedness results for the commutator of Marcinkiewicz integrals with rough kernels. The approach is based on the theory of variable exponent and on generalization of the BMO-norms. У рамках змiнних експонент просторiв Моррея та Моррея – Герца доведено деякi результати щодо обмеженостi комутатора iнтегралiв Марцинкевича з грубими ядрами. Цей пiдхiд базується на теорiї змiнних експонент та уза- гальненнi BMO-норм. 1. Introduction. Let \BbbR n be the n-dimensional Euclidean space of points x = (x1, . . . , xn) with norm | x| = \Bigl( \sum n i=1 x2i \Bigr) 1/2 . Suppose that \BbbS n - 1 is the unit sphere in \BbbR n, n \geq 2, equipped with the normalized Lebesgue measure d\sigma (x\prime ). Let \Omega \in L1(\BbbS n - 1) be homogeneous of degree zero and satisfy \int \BbbS n - 1 \Omega (x\prime )d\sigma (x\prime ) = 0, (1) where x\prime = x/| x| for any x \not = 0. Then the Marcinkiewicz integral operator \mu \Omega of higher dimension is defined by \mu \Omega (f)(x) = \left( \infty \int 0 | F\Omega ,t(f)(x)| 2 dt t3 \right) 1 2 , where F\Omega ,t(f)(x) = \int | x - y| \leq t \Omega (x - y) | x - y| n - 1 f(y)dy. A locally integrable function b is said to be a \mathrm{B}\mathrm{M}\mathrm{O}(\BbbR n) function, if it satisfies \| b\| \ast := \mathrm{s}\mathrm{u}\mathrm{p} x\in \BbbR n,r>0 1 | B| \int B | b(y) - bB| dy < \infty , where B is ball centered at x and radius of r, bB = 1 | B| \int B b(t)dt and \| b\| \ast is the norm in \mathrm{B}\mathrm{M}\mathrm{O}(\BbbR n). For b \in \mathrm{B}\mathrm{M}\mathrm{O}(\BbbR n), the commutator of the Marcinkiewicz integral operator \mu \Omega ,b, is then * This research was supported by NNSF of China (Grant No. 11871096), Anhui Provincial Natural Science Foundation (Grant No. 1908085MA19) and Pre-research Project of the NNSF of China (Grant No. 2019yyzr14). c\bigcirc M. QU, L. WANG, 2020 928 ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 929 defined by \mu \Omega ,b(f) = \left( \infty \int 0 \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \int | x - y| \leq t \Omega (x - y) | x - y| n - 1 (b(x) - b(y))f(y)dy \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| 2 dt t3 \right) 1 2 . It is well-known that Stein [23] first proved that if \Omega \in \mathrm{L}\mathrm{i}\mathrm{p}\gamma (\BbbS n - 1), 0 < \gamma \leq 1, then \mu \Omega is of type (p, p) for 1 < p \leq 2 and of weak type (1, 1). Afterwards, Ding, Fan and Pan [7] removed the smoothness assumed on \Omega and showed that \mu \Omega is bounded on Lp(\BbbR n) for 1 < p < \infty if \Omega \in H1(\BbbS n - 1). Here H1(\BbbS n - 1) denotes the classical Hardy space on \BbbS n - 1. On the other hand, using a good-\lambda inequality, Torchinsky and Wang [25] established the weighted Lp-boundedness of \mu \Omega and \mu \Omega ,b when \Omega \in \mathrm{L}\mathrm{i}\mathrm{p}\gamma (\BbbS n - 1), 0 < \gamma \leq 1. For some recent development, we refer to [2, 8, 14 – 18] and their references. In recent years, following the fundamental work of Kováčik and Rákosnı́k [13], function spaces with variable exponent, such as the vaiable exponent Lebesgue, Herz and Morrey spaces etc., have attracted a great attention due mainly to their useful applications in fluid dynamics, image restoration and differential equations with p(x)-growth (see [1, 3, 11, 30 – 32] and the references therein). In many applications, a crucial step has been to prove that the classical operators are bounded in variable exponent function spaces. Ho in [9, 10] has given some sufficient conditions for the boundedness of fractional operators and singular integral operators in variable exponent Morrey spaces \scrM p(\cdot ),u, where u is a Morrey weight function for Lp(\cdot )(\BbbR n) (see Definition 3.1). In 2016, Tao and Li [26] showed that if \Omega \in \mathrm{L}\mathrm{i}\mathrm{p}\gamma (\BbbS n - 1), 0 < \gamma \leq 1, then the commutator \mu \Omega ,b is bounded on \scrM p(\cdot ),u. On the other hand, based on the extrapolation theory and some pointwise estimates, operators with rough kernels have recently been discussed in [5, 22, 27]. These results inspire us to consider the question: whether the variable exponent Morrey spaces estimates for \mu \Omega ,b are still true if \Omega \in Ls(\BbbS n - 1), s > 1? The first aim of this paper is to give an affirmative answer to this question. Morrey – Herz spaces M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) with variable exponents p and \alpha were recently studied by Lu and Zhu [20]. Under natural regularity assumptions on the exponent \alpha and p, either at the origin or at infinity, they established the boundedness of a wide class of sublinear operators (including ma- ximal, potential and Calderón – Zygmund operators) and their commutators on such spaces. In [29], we made a further step and generalized the main theorems in [20] to the case of rough kernels. Mo- tivated by the work of [20] and [29], the second aim of this paper is to prove that \mu \Omega ,b is bounded on M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) provided that \lambda \geq 0 and \alpha , p are variable exponents. This result improves the corres- ponding main theorem in [28], where the authors considered only the case \lambda = 0 and \alpha is a constant. We usually denote cubes in \BbbR n by Q, | Q| is the Lebesgue measure of Q. \chi E is a characteristic function of a measurable set E \subset \BbbR n. Let Bl = \{ x \in \BbbR n : | x| \leq 2l\} , l \in \BbbZ , and B := B(x, r) = = \{ y \in \BbbR n : | x - y| < r\} . fB means the integral average of f on B, namely, fB = 1 | B| \int B f(x)dx. p\prime (\cdot ) denotes the conjugate exponent defined by 1/p(\cdot ) + 1/p\prime (\cdot ) = 1. The letter C stands for a positive constant, which may vary from line to line. The expression f \lesssim g means that f \leq Cg, and f \thickapprox g means f \lesssim g \lesssim f. 2. Preliminaries and lemmas. We begin with a brief and necessarily incomplete review of the variable exponent Lebesgue spaces Lp(\cdot )(\BbbR n) (see [4, 6] for more information). ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 930 M. QU, L. WANG Given a measurable function p, we assume that 1 < p - \leq p(x) \leq p+ < \infty , (2) where p - := ess infx\in \BbbR np(x) and p+ := ess supx\in \BbbR np(x). By Lp(\cdot )(\BbbR n) we denote the set of all measurable functions f on \BbbR n such that Ip(\cdot )(f) := \int \BbbR n | f(x)| p(x)dx < \infty . This is a Banach space with the norm (the Luxemburg – Nakano norm) \| f\| Lp(\cdot )(\BbbR n) = inf\{ \mu > 0 : Ip(\cdot )(f/\mu ) \leq 1\} . It is easy to see that this norm has the following property: \| | f | \sigma \| Lp(\cdot )(\BbbR n) = \| f\| \sigma L\sigma p(\cdot )(\BbbR n) , \sigma \geq 1/p - . (3) By \scrP (\BbbR n) we denote the set of variable exponents p(\cdot ) satisfying (2). When p(\cdot ) \in \scrP (\BbbR n), the generalized H\"\mathrm{o}lder inequality holds in the form\int \BbbR n | f(x)g(x)| dx \leq rp\| f\| Lp(\cdot )(\BbbR n)\| g\| Lp\prime (\cdot )(\BbbR n) (4) with rp = 1 + 1/p - - 1/p+ (see [13], Theorem 2.1). The set \scrB (\BbbR n) consists of p(\cdot ) \in \scrP (\BbbR n) satisfying the condition that M is bounded on Lp(\cdot )(\BbbR n), where M denotes the Hardy – Littlewood maximal operator defined by Mf(x) = \mathrm{s}\mathrm{u}\mathrm{p} r>0 1 | B(x, r)| \int B(x,r) | f(y)| dy. It is well-known that if p(\cdot ) \in \scrB (\BbbR n), then p\prime (\cdot ) \in \scrB (\BbbR n) (see [12], Proposition 2). A function \phi (\cdot ) : \BbbR n \rightarrow \BbbR is called log-H\"older continuous at the origin (or has a log decay at the origin), if there exists a constant Clog > 0 such that | \phi (x) - \phi (0)| \leq Clog log(e+ 1/| x| ) , x \in \BbbR n. If, for some \phi \infty \in \BbbR and Clog > 0, there holds | \phi (x) - \phi \infty | \leq Clog log(e+ | x| ) , x \in \BbbR n, then \phi (\cdot ) is called log-H\"older continuous at infinity (or has a log decay at the infinity). Lemma 2.1. If p(\cdot ) \in \scrB (\BbbR n), then we have \| \chi B\| Lp(\cdot )(\BbbR n)\| \chi B\| Lp\prime (\cdot )(\BbbR n) \lesssim | B| . ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 931 Lemma 2.2. If p(\cdot ) \in \scrB (\BbbR n), then we have, for all measurable subsets E \subset B, \| \chi E\| Lp(\cdot )(\BbbR n) \| \chi B\| Lp(\cdot )(\BbbR n) \lesssim \biggl( | E| | B| \biggr) \delta 1 , \| \chi E\| Lp\prime (\cdot )(\BbbR n) \| \chi B\| Lp\prime (\cdot )(\BbbR n) \lesssim \biggl( | E| | B| \biggr) \delta 2 , where \delta 1, \delta 2 are constants with 0 < \delta 1, \delta 2 < 1. Lemma 2.3. If p(\cdot ) \in \scrB (\BbbR n), b \in \mathrm{B}\mathrm{M}\mathrm{O}(\BbbR n), k > j, k, j \in \BbbN , then we have \mathrm{s}\mathrm{u}\mathrm{p} B\subset \BbbR n 1 \| \chi B\| Lp(\cdot )(\BbbR n) \| (b - bB)\chi B\| Lp(\cdot )(\BbbR n) \thickapprox \| b\| \ast , \| (b - bBj )\chi Bk \| Lp(\cdot )(\BbbR n) \lesssim (k - j)\| b\| \ast \| \chi Bk \| Lp(\cdot )(\BbbR n). Lemmas 2.1 – 2.3 are due to Izuki [12]. Lemma 2.4. Let p(\cdot ) \in \scrP (\BbbR n). If q > p+ and 1 p(x) = 1\widetilde q(x) + 1 q , then we have \| fg\| Lp(\cdot )(\BbbR n) \lesssim \| f\| L\widetilde q(\cdot )(\BbbR n)\| g\| Lq(\BbbR n) for all measurable functions f and g. Lemma 2.5. Let r1 > 0. Suppose \alpha (\cdot ) \in L\infty (\BbbR n) is log-H\"older continuous both at origin and at infinity, then we have r \alpha (x) 1 \lesssim r \alpha (y) 2 \times \left\{ \biggl( r1 r2 \biggr) \alpha + , 0 < r2 \leq r1/2, 1, r1/2 < r2 \leq 2r1,\biggl( r1 r2 \biggr) \alpha - , r2 > 2r1, for any x \in B(0, r1)\setminus B(0, r1/2) and y \in B(0, r2)\setminus B(0, r2/2). The proof of Lemmas 2.4 and 2.5 can be found in [21] and [1], respectively. 3. Boundedness on variable exponent Morrey spaces. We first recall the following definitions given by Ho in [9]. Definition 3.1. Let p(\cdot ) \in L\infty (\BbbR n). A Lebesgue measurable function u(z, r) : \BbbR n\times (0,+\infty ) \rightarrow \rightarrow (0,+\infty ) is said to be a Morrey weight function for Lp(\cdot )(\BbbR n) if u satisfies \infty \sum j=0 \| \chi B(z,r)\| Lp(\cdot )(\BbbR n) \| \chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n) u(z, 2j+1r) \lesssim u(z, r) (5) for any z \in \BbbR n and r > 0. By \BbbW p(\cdot ), we denote the class of Morrey weight functions. We note that condition (5) is also used to study the Fefferman – Stein vector-valued inequalities in weighted Morrey spaces (see [10]). For any p(\cdot ) \in \scrB (\BbbR n), let \scrK p(\cdot ) denote the supremum of those q > 1 such that p(\cdot )/q \in \scrB (\BbbR n) and \scrE p(\cdot ) be the conjugate of \scrK p\prime (\cdot ). The following result can be seen as a special case of the general result in [10] for Banach function spaces. ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 932 M. QU, L. WANG Proposition 3.1. Let p(\cdot ) \in \scrB (\BbbR n). For any 1 < q < \scrK p(\cdot ) and 1 < \tau < \scrK p\prime (\cdot ), we have, for any z \in \BbbR n and r > 0, 2jn(1 - 1 \tau ) \lesssim \| \chi B(z,2jr)\| Lp(\cdot )(\BbbR n) \| \chi B(z,r)\| Lp(\cdot )(\BbbR n) \lesssim 2 jn q \forall j \in \BbbN . (6) Remark 3.1. It is easy to check that condition (5) together with (6) yields u(z, 2r) \lesssim u(z, r) for any z \in \BbbR n and r > 0. Definition 3.2. Let p(\cdot ) \in \scrB (\BbbR n) and u \in \BbbW p(\cdot ). The variable Morrey space \scrM p(\cdot ),u is the collection of all Lebesgue measurable functions f satisfying \| f\| \scrM p(\cdot ),u = \mathrm{s}\mathrm{u}\mathrm{p} z\in \BbbR n,R>0 1 u(z,R) \| f\chi B(z,R)\| Lp(\cdot )(\BbbR n) < \infty . Now, let us state the main result in this section. Theorem 3.1. Suppose p(\cdot ) \in \scrB (\BbbR n) and \Omega \in Ls(\BbbS n - 1) with s > (p\prime )+ is homogeneous of degree zero and satisfies (1). If b \in \mathrm{B}\mathrm{M}\mathrm{O}(\BbbR n) and \infty \sum j=0 (j + 1) \| \chi B(z,r)\| Lp(\cdot )(\BbbR n) \| \chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n) u(z, 2j+1r) \lesssim u(z, r), (7) for any z \in \BbbR n and r > 0, then we have \| \mu \Omega ,b(f)\| \scrM p(\cdot ),u \lesssim \| b\| \ast \| f\| \scrM p(\cdot ),u . Remark 3.2. Clearly, in comparison with the corresponding result by Tao and Li in [26, p. 56], the smoothness condition on \Omega has been removed. More precisely, our result is an improvement of Theorem 1.4 in [26]. Remark 3.3. There do exist some functions satisfying condition (7). For instance, if, for any 0 \leq \gamma < 1/\scrE p(\cdot ), a weight function u satisfies u(z, 2r) \leq 2n\gamma u(z, r) for any z \in \BbbR n and r > 0, then (7) holds. In fact, for any \gamma < 1/\scrE p(\cdot ), there always exists a \tau < 1/\scrK p\prime (\cdot ) such that \gamma < 1 - 1/\tau < < 1 - 1/\scrK p\prime (\cdot ) = 1/\scrE p(\cdot ). An application of Proposition 3.1 gives \infty \sum j=0 (j + 1) \| \chi B(z,r)\| Lp(\cdot )(\BbbR n) \| \chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n) u(z, 2j+1r) u(z, r) \lesssim \infty \sum j=0 (j + 1)2jn( 1 \tau +\gamma - 1) \lesssim 1. Proof of Theorem 3.1. Let f \in \scrM p(\cdot ),u. For any z \in \BbbR n and r > 0, we decompose f = g + h, where g = f\chi B(z,2r) and h = \sum \infty j=1 f\chi B(z,2j+1r)\setminus B(z,2jr). Noting that \mu \Omega ,b is a nonlinear operator, then we have 1 u(z, r) \| \chi B(z,r)\mu \Omega ,b(f)\| Lp(\cdot )(\BbbR n) \leq 1 u(z, r) \| \chi B(z,r)\mu \Omega ,b(g)\| Lp(\cdot )(\BbbR n)+ + 1 u(z, r) \| \chi B(z,r)\mu \Omega ,b(h)\| Lp(\cdot )(\BbbR n) := I + II. For I, using u(z, 2r) \lesssim u(z, r) and the Lp(\cdot )(\BbbR n)-boundedness of \mu \Omega ,b (see [28, p. 262]), we obtain ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 933 I \lesssim \| b\| \ast 1 u(z, 2r) \| f\chi B(z,2r)\| Lp(\cdot )(\BbbR n) \lesssim \lesssim \| b\| \ast \mathrm{s}\mathrm{u}\mathrm{p} z\in \BbbR n,R>0 1 u(z,R) \| f\chi B(z,R)\| Lp(\cdot )(\BbbR n) \lesssim \| b\| \ast \| f\| \scrM p(\cdot ),u . For II, we note that if x \in B(z, r) and y \in \widetilde Rj := B(z, 2j+1r) \setminus B(z, 2jr), then | x - y| \approx \approx | y - z| \approx 2jr. The Minkowski inequality yields | \mu \Omega ,b(h)(x)| \lesssim \infty \sum j=1 \left\{ \int \widetilde Rj | \Omega (x - y)| | x - y| n - 1 | b(x) - b(y)| | f(y)| \left( \int | x - y| <t dt t3 \right) 1/2 dy \right\} \lesssim \lesssim \infty \sum j=1 1 (2jr)n \int \widetilde Rj | b(x) - b(y)| | \Omega (x - y)| | f(y)| dy \lesssim \lesssim \infty \sum j=1 1 (2jr)n | b(x) - bB(z,r)| \int \widetilde Rj | \Omega (x - y)| | f(y)| dy+ + \infty \sum j=1 1 (2jr)n | bB(z,2j+1r) - bB(z,r)| \int \widetilde Rj | \Omega (x - y)| | f(y)| dy+ + \infty \sum j=1 1 (2jr)n \int \widetilde Rj | b(y) - bB(z,2j+1r)| | \Omega (x - y)| | f(y)| dy := := U1 + U2 + U3. For U1, since s > (p\prime )+, then we can choose p\ast (\cdot ) > 0 such that 1 s\prime = 1 p(x) + 1 p\ast (x) , by the property (3) and the generalized H\"\mathrm{o}lder inequality (4), we get \| f\chi B(z,2j+1r)\| Ls\prime (\BbbR n) \lesssim \| f\chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n)\| \chi B(z,2j+1r)\| Lp\ast (\cdot )(\BbbR n). (8) In view of 1 p\ast (\cdot ) = 1 s\prime - 1 p(\cdot ) = 1 p\prime (\cdot ) - 1 s , Lemma 2.4 in [27, p. 178] yields \| \chi B(z,2j+1r)\| Lp\ast (\cdot )(\BbbR n) \approx (2jr) - n s \| \chi B(z,2j+1r)\| Lp\prime (\cdot )(\BbbR n). (9) Thus, from (8), (9) and the H\"\mathrm{o}lder inequality, it follows that U1 \lesssim \infty \sum j=1 1 (2jr)n | b(x) - bB(z,r)| \| f\chi B(z,2j+1r)\| Ls\prime (\BbbR n) \left( \int \widetilde Rj | \Omega (x - y)| sdy \right) 1 s \lesssim ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 934 M. QU, L. WANG \lesssim \infty \sum j=1 1 (2jr)n | b(x) - bB(z,r)| \| f\chi B(z,2j+1r)\| Ls\prime (\BbbR n) \left( \int | x - y| \lesssim 2jr | \Omega (x - y)| sdy \right) 1 s \lesssim \lesssim \infty \sum j=1 1 (2jr)n(1 - 1 s ) | b(x) - bB(z,r)| \| f\chi B(z,2j+1r)\| Ls\prime (\BbbR n) \lesssim \lesssim \infty \sum j=1 1 (2jr)n | b(x) - bB(z,r)| \| f\chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n)\| \chi B(z,2j+1r)\| Lp\prime (\cdot )(\BbbR n). For U2, noting that | bB(z,2j+1r) - bB(z,r)| \lesssim (j + 1)\| b\| \ast (see [24, p. 206]), we have U2 \lesssim \infty \sum j=1 1 (2jr)n | bB(z,2j+1r) - bB(z,r)| \| f\chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n)\| \chi B(z,2j+1r)\| Lp\prime (\cdot )(\BbbR n) \lesssim \lesssim \infty \sum j=1 (j + 1) 1 (2jr)n \| b\| \ast \| f\chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n)\| \chi B(z,2j+1r)\| Lp\prime (\cdot )(\BbbR n). For U3, applying Lemma 2.3 with B = B(z, 2j+1r), (8) and (9), we obtain U3 \lesssim \infty \sum j=1 1 (2jr)n(1 - 1 s ) \| (b - bB(z,2j+1r))f\chi B(z,2j+1r)\| Ls\prime (\BbbR n) \lesssim \lesssim \infty \sum j=1 1 (2jr)n \| f\chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n)\| (b - bB(z,2j+1r))\chi B(z,2j+1r)\| Lp\prime (\cdot )(\BbbR n) \lesssim \lesssim \infty \sum j=1 1 (2jr)n \| b\| \ast \| f\chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n)\| \chi B(z,2j+1r)\| Lp\prime (\cdot )(\BbbR n). Combining the estimate of U1, U2 and U3, by Lemmas 2.3 and 2.1, we get \| \chi B(z,r)\mu \Omega ,b(h)\| Lp(\cdot )(\BbbR n) \lesssim \lesssim \infty \sum j=1 (j + 1) 1 (2jr)n \| b\| \ast \| \chi B(z,r)\| Lp(\cdot )(\BbbR n)\| f\chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n)\| \chi B(z,2j+1r)\| Lp\prime (\cdot )(\BbbR n) \lesssim \lesssim \| b\| \ast \infty \sum j=1 (j + 1) \| \chi B(z,r)\| Lp(\cdot )(\BbbR n) \| \chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n) u(z, 2j+1r)\times \times \mathrm{s}\mathrm{u}\mathrm{p} z\in \BbbR n,R>0 1 u(z,R) \| f\chi B(z,R)\| Lp(\cdot )(\BbbR n) \lesssim \lesssim \| b\| \ast \infty \sum j=1 (j + 1) \| \chi B(z,r)\| Lp(\cdot )(\BbbR n) \| \chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n) u(z, 2j+1r)\| f\| \scrM p(\cdot ),u . ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 935 Thus, in view of the condition (7), we arrive at the desired inequality II = 1 u(z, r) \| \chi B(z,r)\mu \Omega ,b(h)\| Lp(\cdot )(\BbbR n) \lesssim \lesssim \| b\| \ast \| f\| \scrM p(\cdot ),u \infty \sum j=1 (j + 1) \| \chi B(z,r)\| Lp(\cdot )(\BbbR n) \| \chi B(z,2j+1r)\| Lp(\cdot )(\BbbR n) u(z, 2j+1r) u(z, r) \lesssim \| b\| \ast \| f\| \scrM p(\cdot ),u . Theorem 3.1 is proved. 4. Boundedness on variable exponent Morrey – Herz spaces. Let Bk = \{ x \in \BbbR n : | x| \leq 2k\} , Rk = Bk\setminus Bk - 1 and \chi k = \chi Rk be the characteristic function of the set Rk for k \in \BbbZ . Definition 4.1. Let 0 < q \leq \infty , p(\cdot ) \in \scrP (\BbbR n) and \alpha (\cdot ) : \BbbR n \rightarrow \BbbR with \alpha (\cdot ) \in L\infty (\BbbR n). The homogeneous Herz space \.K \alpha (\cdot ) p(\cdot ),q(\BbbR n) is defined as the class of all f \in L p(\cdot ) loc (\BbbR n\setminus \{ 0\} ) such that \| f\| \.K \alpha (\cdot ) p(\cdot ),q(\BbbR n) := \Biggl( \sum k\in \BbbZ \| 2k\alpha (\cdot )f\chi k\| qLp(\cdot )(\BbbR n) \Biggr) 1/q < \infty with the usual modification when q = \infty . Definition 4.2. Let 0 \leq \lambda < \infty , 0 < q \leq \infty , p(\cdot ) \in \scrP (\BbbR n) and \alpha (\cdot ) : \BbbR n \rightarrow \BbbR with \alpha (\cdot ) \in L\infty (\BbbR n). The homogeneous Morrey – Herz space M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) is defined as the class of all f \in L p(\cdot ) loc (\BbbR n\setminus \{ 0\} ) such that \| f\| M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) := \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda \Biggl( k0\sum k= - \infty \| 2k\alpha (\cdot )f\chi k\| qLp(\cdot )(\BbbR n) \Biggr) 1/q < \infty with the usual modification when q = \infty . Remark 4.1. It obviously follows that M \.K \alpha (\cdot ),0 q,p(\cdot ) (\BbbR n) = \.K \alpha (\cdot ) p(\cdot ),q(\BbbR n). If both \alpha (\cdot ) and p(\cdot ) are constants, then M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) coincides with the classical Morrey – Herz spaces M \.K\alpha ,\lambda p,q (\BbbR n) defined in [19]. Lu and Zhu [20] obtained the following result. Proposition 4.1. Let 0 \leq \lambda < \infty , 0 < q \leq \infty , p(\cdot ) \in \scrP (\BbbR n) and \alpha (\cdot ) \in L\infty (\BbbR n). If \alpha (\cdot ) is log-H\"older continuous both at origin and at infinity, then \| f\| M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) \approx \mathrm{m}\mathrm{a}\mathrm{x} \left\{ \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda \Biggl( k0\sum k= - \infty 2k\alpha (0)q\| f\chi k\| qLp(\cdot )(\BbbR n) \Biggr) 1/q , \mathrm{s}\mathrm{u}\mathrm{p} k0\geq 0,k0\in \BbbZ \left[ 2 - k0\lambda \Biggl( - 1\sum k= - \infty 2k\alpha (0)q\| f\chi k\| qLp(\cdot )(\BbbR n) \Biggr) 1/q + 2 - k0\lambda \Biggl( k0\sum k=0 2k\alpha \infty q\| f\chi k\| qLp(\cdot )(\BbbR n) \Biggr) 1/q \right] \right\} . The results obtained in this section can be summarized as follows. Theorem 4.1. Suppose b \in \mathrm{B}\mathrm{M}\mathrm{O}(\BbbR n), p(\cdot ) \in \scrB (\BbbR n) and \Omega \in Ls(\BbbS n - 1) with s > (p\prime )+ is homogeneous of degree zero and satisfies (1). Let \lambda > 0, 0 < q \leq \infty and \alpha (\cdot ) \in L\infty (\BbbR n) be log-H\"older continuous both at the origin and at infinity such that ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 936 M. QU, L. WANG \lambda - n\delta 1 < \alpha - \leq \alpha + < n\delta 2 - (n - 1)/s, where 0 < \delta 1, \delta 2 < 1 are the constants appearing in Lemma 2.2. Then the commutator \mu \Omega ,b is bounded on M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n). We would like to point out that Theorem 4.1 is still true in the particular case \lambda = 0, namely, in the framework of Herz spaces with variable exponents. By using the same method of proving Theorem 4.1, we get the following corollary. Corollary 4.1. Suppose b \in \mathrm{B}\mathrm{M}\mathrm{O}(\BbbR n), p(\cdot ) \in \scrB (\BbbR n) and \Omega \in Ls(\BbbS n - 1) with s > (p\prime )+ is homogeneous of degree zero and satisfies (1). Let 0 < q \leq \infty and \alpha (\cdot ) \in L\infty (\BbbR n) be log-H\"older continuous both at the origin and at infinity such that - n\delta 1 < \alpha - \leq \alpha + < n\delta 2 - (n - 1)/s, where 0 < \delta 1, \delta 2 < 1 are the constants appearing in Lemma 2.2. Then the commutator \mu \Omega ,b is bounded on \.K \alpha (\cdot ) p(\cdot ),q(\BbbR n). Proof of Theorem 4.1. Let f \in M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n). We decompose f(x) = \infty \sum j= - \infty f(x)\chi j(x) = \infty \sum j= - \infty fj(x). The Minkowski inequality implies that \| \mu \Omega ,b(f)\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) = \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \bigm\| \bigm\| \bigm\| 2k\alpha (\cdot )| \mu \Omega ,b(f)| \chi k \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| 2k\alpha (\cdot ) \left( k - 2\sum j= - \infty | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) + + \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| 2k\alpha (\cdot ) \left( k+1\sum j=k - 1 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) + + \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| 2k\alpha (\cdot ) \left( \infty \sum j=k+2 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) := := V1 + V2 + V3. For V1, noticing that | x - y| \approx | x| \approx 2k for x \in Rk, y \in Rj and j \leq k - 2, then we have | \mu \Omega ,b(fj)(x)| \lesssim \left( | x| \int 0 \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \int | x - y| \leq t (b(x) - b(y)) \Omega (x - y) | x - y| n - 1 fj(y)dy \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| 2 dt t3 \right) 1 2 + ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 937 + \left( \infty \int | x| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \int | x - y| \leq t (b(x) - b(y)) \Omega (x - y) | x - y| n - 1 fj(y)dy \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| 2 dt t3 \right) 1 2 \lesssim \lesssim \int Rj | b(x) - b(y)| | \Omega (x - y)| | fj(y)| | x - y| n - 1 | y| 1 2 | x - y| 3 2 dy+ + \int Rj | b(x) - b(y)| | \Omega (x - y)| | fj(y)| | x - y| n - 1 1 | x| dy \lesssim \lesssim 2 - kn \int Rj | b(x) - b(y)| | \Omega (x - y)| | fj(y)| dy. This together with Lemma 2.5 yields 2k\alpha (x) k - 2\sum j= - \infty | \mu \Omega ,b(fj)(x)| \chi k(x) \lesssim \lesssim k - 2\sum j= - \infty 2 - kn \int Rj 2k\alpha (x)| \Omega (x - y)| | b(x) - b(y)| | fj(y)| dy \cdot \chi k(x) \lesssim \lesssim k - 2\sum j= - \infty 2 - kn2(k - j)\alpha + \int Rj 2j\alpha (y)| \Omega (x - y)| | b(x) - b(y)| | fj(y)| dy \cdot \chi k(x) \lesssim \lesssim k - 2\sum j= - \infty 2 - kn2(k - j)\alpha + \left( | b(x) - bBj | \int Rj 2j\alpha (y)| \Omega (x - y)| | fj(y)| dy+ + \int Rj 2j\alpha (y)| bBj - b(y)| | \Omega (x - y)| | fj(y)| dy \right) \cdot \chi k(x). (10) Define a variable exponent p\ast (\cdot ) by 1 p\prime (x) = 1 p\ast (x) + 1 s , since s > (p\prime )+, using the fact that \| \chi Bj\| Lp\ast (\cdot )(\BbbR n) \approx \| \chi Bj\| Lp\prime (\cdot )(\BbbR n)| Bj | - 1/s (see [28, p. 258]) and Lemma 2.4, we obtain \| \Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n) \lesssim \| \Omega (x - \cdot )\chi j\| Ls(\BbbR n)\| \chi j\| Lp\ast (\cdot )(\BbbR n) \lesssim \lesssim \left( | x| +2j\int | x| - 2j \int \BbbS n - 1 | \Omega (y\prime )| sd\sigma (y\prime )\varrho n - 1d\varrho \right) 1 s \| \chi Bj\| Lp\prime (\cdot )(\BbbR n)| Bj | - 1/s \lesssim \lesssim 2(k - j)(n - 1)/s\| \chi Bj\| Lp\prime (\cdot )(\BbbR n). (11) ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 938 M. QU, L. WANG An application of Lemmas 2.3, 2.4 and (11) gives \| (b - bBj )\Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n) \lesssim \| (b - bBj )\chi j\| Lp\ast (\cdot )(\BbbR n)\| \Omega (x - \cdot )\chi j\| Ls(\BbbR n) \lesssim \lesssim \| b\| \ast \| \chi Bj\| Lp\ast (\cdot )(\BbbR n)\| \Omega (x - \cdot )\chi j\| Ls(\BbbR n) \lesssim 2(k - j)(n - 1)/s\| \chi Bj\| Lp\prime (\cdot )(\BbbR n). (12) Then, from (10) – (12), (4) and Lemmas 2.1 – 2.3, we deduce\bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| 2k\alpha (\cdot ) k - 2\sum j= - \infty | \mu \Omega ,b(fj)| \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| Lp(\cdot )(\BbbR n) \lesssim \lesssim k - 2\sum j= - \infty 2 - kn2(k - j)\alpha +\| 2j\alpha (\cdot )fj\| Lp(\cdot )(\BbbR n) \Bigl( \| (b - bBj )\chi k\| Lp(\cdot )(\BbbR n)\| \Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n) + + \| (b - bBj )\Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n)\| \chi k\| Lp(\cdot )(\BbbR n) \Bigr) \lesssim \lesssim k - 2\sum j= - \infty 2 - kn2(k - j)\alpha +\| 2j\alpha (\cdot )fj\| Lp(\cdot )(\BbbR n) \Bigl( (k - j)2(k - j)(n - 1)/s\| \chi Bj\| Lp\prime (\cdot )(\BbbR n)\| \chi Bk \| Lp(\cdot )(\BbbR n) + + 2(k - j)(n - 1)/s\| \chi Bj\| Lp\prime (\cdot )(\BbbR n)\| \chi Bk \| Lp(\cdot )(\BbbR n) \Bigr) \lesssim \lesssim k - 2\sum j= - \infty (k - j)2 - kn2(k - j)(\alpha +(n - 1)/s)\| 2j\alpha (\cdot )fj\| Lp(\cdot )(\BbbR n)\| \chi Bj\| Lp\prime (\cdot )(\BbbR n)\| \chi Bk \| Lp(\cdot )(\BbbR n) \lesssim \lesssim k - 2\sum j= - \infty (k - j)2(k - j)(\alpha ++(n - 1)/s)\| 2j\alpha (\cdot )fj\| Lp(\cdot )(\BbbR n) \| \chi Bj\| Lp\prime (\cdot )(\BbbR n) \| \chi Bk \| Lp\prime (\cdot )(\BbbR n) \lesssim \lesssim k - 2\sum j= - \infty (k - j)2(j - k)(n\delta 2 - \alpha + - (n - 1)/s)\| 2j\alpha (\cdot )fj\| Lp(\cdot )(\BbbR n). Therefore, we arrive at the estimate V1 \thickapprox \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| 2k\alpha (\cdot ) \left( k - 2\sum j= - \infty | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \left( k - 2\sum j= - \infty (k - j)2(j - k)(n\delta 2 - \alpha + - (n - 1)/s)\| 2j\alpha (\cdot )fj\| Lp(\cdot )(\BbbR n) \right) q . Now we can distinguish two cases as follows: Case 1\circ . If 0 < q \leq 1, using the well-known inequality\left( \infty \sum j=1 aj \right) q \leq \infty \sum j=1 aqj , aj > 0, j = 1, 2, . . . , (13) ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 939 we obtain V1 \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty k - 2\sum j= - \infty (k - j)q2(j - k)(n\delta 2 - \alpha + - (n - 1)/s)q\| 2j\alpha (\cdot )fj\| qLp(\cdot )(\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0 - 2\sum j= - \infty \| 2j\alpha (\cdot )fj\| qLp(\cdot )(\BbbR n) k0\sum k=j+2 (k - j)q2(j - k)(n\delta 2 - \alpha + - (n - 1)/s)q \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0 - 2\sum j= - \infty \| 2j\alpha (\cdot )fj\| qLp(\cdot )(\BbbR n) \lesssim \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) . Case 2\circ . If 1 < q < \infty , the H\"\mathrm{o}lder inequality implies that V1 \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \left( k - 2\sum j= - \infty 2(j - k)(n\delta 2 - \alpha + - (n - 1)/s)q/2\| 2j\alpha (\cdot )fj\| qLp(\cdot )(\BbbR n) \right) \times \times \left( k - 2\sum j= - \infty (k - j)q \prime 2(j - k)(n\delta 2 - \alpha + - (n - 1)/s)q\prime /2 \right) q/q\prime \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0\in \BbbZ 2 - k0\lambda q k0 - 2\sum j= - \infty \| 2j\alpha (\cdot )fj\| qLp(\cdot )(\BbbR n) k0\sum k=j+2 2(j - k)(n\delta 2 - \alpha + - (n - 1)/s)q/2 \lesssim \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) . We proceed now to estimate V2. By Proposition 4.1 and the Lp(\cdot )(\BbbR n)-boundedness of the com- mutator \mu \Omega ,b, we get V2 \approx max \left\{ \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \left( k+1\sum j=k - 1 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) , \mathrm{s}\mathrm{u}\mathrm{p} k0\geq 0,k0\in \BbbZ \left[ 2 - k0\lambda q - 1\sum k= - \infty 2k\alpha (0)q \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \left( k+1\sum j=k - 1 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) + +2 - k0\lambda q k0\sum k=0 2k\alpha \infty q \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \left( k+1\sum j=k - 1 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) \right] \right\} \lesssim \lesssim max \Biggl\{ \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \bigm\| \bigm\| \bigm\| 2k\alpha \infty | f\chi k| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) , \mathrm{s}\mathrm{u}\mathrm{p} k0\geq 0,k0\in \BbbZ \Biggl[ 2 - k0\lambda q - 1\sum k= - \infty \bigm\| \bigm\| \bigm\| 2k\alpha \infty | f\chi k| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) + 2 - k0\lambda q k0\sum k=0 \bigm\| \bigm\| \bigm\| 2k\alpha \infty | f\chi k| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) \Biggr] \Biggr\} \lesssim ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 940 M. QU, L. WANG \lesssim \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) . For V3, once again by Proposition 4.1, we have V3 \approx max\{ E,F\} , where E = \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \left( \infty \sum j=k+2 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) , F = \mathrm{s}\mathrm{u}\mathrm{p} k0\geq 0,k0\in \BbbZ \left\{ 2 - k0\lambda q - 1\sum k= - \infty 2k\alpha (0)q \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \left( \infty \sum j=k+2 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) + +2 - k0\lambda q k0\sum k=0 2k\alpha \infty q \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \left( \infty \sum j=k+2 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) \right\} . For E, noticing that | x - y| \approx | y| \approx 2j for x \in Rk, y \in Rj and j \geq k + 2, then we obtain | \mu \Omega ,b(fj)(x)| \lesssim \left( | y| \int 0 \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \int | x - y| \leq t (b(x) - b(y)) \Omega (x - y) | x - y| n - 1 fj(y)dy \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| 2 dt t3 \right) 1 2 + + \left( \infty \int | y| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \int | x - y| \leq t (b(x) - b(y)) \Omega (x - y) | x - y| n - 1 fj(y)dy \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| \bigm| 2 dt t3 \right) 1 2 \lesssim \lesssim \int Rj | b(x) - b(y)| | \Omega (x - y)| | fj(y)| | x - y| n - 1 | x| 1 2 | x - y| 3 2 dy+ + \int Rj | b(x) - b(y)| | \Omega (x - y)| | fj(y)| | x - y| n - 1 1 | y| dy \lesssim \lesssim 2 - jn \int Rj | b(x) - b(y)| | \Omega (x - y)| | fj(y)| dy \lesssim \lesssim 2 - jn\| fj\| Lp(\cdot )(\BbbR n) \Bigl( | b(x) - bBk | \| \Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n)+ + \| \Omega (x - \cdot )(b - bBk )\chi j\| Lp\prime (\cdot )(\BbbR n) \Bigr) . (14) Similarly to (11), we get ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 941 \| \Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n) \lesssim \| \Omega (x - \cdot )\chi j\| Ls(\BbbR n)\| \chi j\| Lp\ast (\cdot )(\BbbR n) \lesssim \lesssim \left( 2j+1\int 0 \int \BbbS n - 1 | \Omega (y\prime )| sd\sigma (y\prime )\varrho n - 1d\varrho \right) 1 s \| \chi Bj\| Lp\prime (\cdot )(\BbbR n)| Bj | - 1/s \lesssim \lesssim \| \Omega \| Ls(\BbbS n - 1)\| \chi Bj\| Lp\prime (\cdot )(\BbbR n), (15) which in conjunction with Lemma 2.4 implies \| (b - bBk )\Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n) \lesssim \| (b - bBk )\chi j\| Lp\ast (\cdot )(\BbbR n)\| \Omega (x - \cdot )\chi j\| Ls(\BbbR n) \lesssim \lesssim (j - k)\| b\| \ast \| \chi Bj\| Lp\ast (\cdot )(\BbbR n)\| \Omega (x - \cdot )\chi j\| Ls(\BbbR n) \lesssim \lesssim (j - k)\| \chi Bj\| Lp\prime (\cdot )(\BbbR n). (16) Now from (14) – (16) and Lemmas 2.1 – 2.3, we obtain \| \mu \Omega ,b(fj)\chi k\| Lp(\cdot )(\BbbR n) \lesssim 2 - jn\| fj\| Lp(\cdot )(\BbbR n) \Bigl( \| (b - bBk )\chi k\| Lp(\cdot )(\BbbR n)\| \Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n)+ + \| (b - bBk )\Omega (x - \cdot )\chi j\| Lp\prime (\cdot )(\BbbR n)\| \chi k\| Lp(\cdot )(\BbbR n) \Bigr) \lesssim \lesssim (j - k)2 - jn\| fj\| Lp(\cdot )(\BbbR n)\| \chi Bk \| Lp(\cdot )(\BbbR n)\| \chi Bj\| Lp\prime (\cdot )(\BbbR n) \lesssim \lesssim (j - k)\| fj\| Lp(\cdot )(\BbbR n) \| \chi Bk \| Lp(\cdot )(\BbbR n) \| \chi Bj\| Lp(\cdot )(\BbbR n) \lesssim \lesssim (j - k)2(k - j)n\delta 1\| fj\| Lp(\cdot )(\BbbR n). Consequently, we have E = \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \left( \infty \sum j=k+2 | \mu \Omega ,b(fj)| \right) \chi k \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| \bigm\| q Lp(\cdot )(\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q \left( \infty \sum j=k+2 (j - k)2(k - j)n\delta 1\| fj\| Lp(\cdot )(\BbbR n) \right) q . If 0 < q \leq 1, by (13), we get E \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q k0 - 1\sum j=k+2 (j - k)q2(k - j)n\delta 1q\| fj\| qLp(\cdot )(\BbbR n) + + \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q \infty \sum j=k0 (j - k)q2(k - j)n\delta 1q\| fj\| qLp(\cdot )(\BbbR n) := := E1 + E2. ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 942 M. QU, L. WANG For E1, in view of n\delta 1 + \alpha (0) > n\delta 1 + \alpha - > 0, we obtain E1 \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0 - 1\sum j= - \infty 2j\alpha (0)q\| fj\| qLp(\cdot )(\BbbR n) j - 2\sum k= - \infty (j - k)q2(k - j)(n\delta 1+\alpha (0))q \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0 - 1\sum j= - \infty 2j\alpha (0)q\| fj\| qLp(\cdot )(\BbbR n) \lesssim \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) . For E2, noting that \alpha (0) + n\delta 1 - \lambda > \alpha - + n\delta 1 - \lambda > 0, we get E2 \approx \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \infty \sum j=k0 (j - k)q2(k - j)(n\delta 1+\alpha (0))q2j\alpha (0)q\| fj\| qLp(\cdot )(\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \infty \sum j=k0 (j - k)q2(k - j)(n\delta 1+\alpha (0))q2j\lambda q\times \times 2 - j\lambda q j\sum l= - \infty 2l\alpha (0)q\| fl\| qLp(\cdot )(\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\lambda q \infty \sum j=k0 (j - k)q2(k - j)(n\delta 1+\alpha (0) - \lambda )q\| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q \Biggl( k0\sum k= - \infty 2k\lambda q \Biggr) \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) \lesssim \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) . If 1 < q < \infty , we have E \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q \left( k0 - 1\sum j=k+2 (j - k)2(k - j)n\delta 1\| fj\| Lp(\cdot )(\BbbR n) \right) q + + \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\alpha (0)q \left( \infty \sum j=k0 (j - k)2(k - j)n\delta 1\| fj\| Lp(\cdot )(\BbbR n) \right) q := := E3 + E4. For E3, the H\"\mathrm{o}lder inequality yields E3 \approx \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \left( k0 - 1\sum j=k+2 (j - k)2(k - j)(n\delta 1+\alpha (0))2j\alpha (0)\| fj\| Lp(\cdot )(\BbbR n) \right) q \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \left( k0 - 1\sum j=k+2 2(k - j)(n\delta 1+\alpha (0))q/22j\alpha (0)q\| fj\| qLp(\cdot )(\BbbR n) \right) \times ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7 ON THE COMMUTATOR OF MARCINKIEWICZ INTEGRALS WITH ROUGH KERNELS . . . 943 \times \left( k0 - 1\sum j=k+2 (j - k)q \prime 2(k - j)(n\delta 1+\alpha (0))q\prime /2 \right) q/q\prime \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0 - 1\sum j= - \infty 2j\alpha (0)q\| fj\| qLp(\cdot )(\BbbR n) j - 2\sum k= - \infty 2(k - j)(n\delta 1+\alpha (0))q/2 \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0 - 1\sum j= - \infty 2j\alpha (0)q\| fj\| qLp(\cdot )(\BbbR n) \lesssim \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) . For E4, as argued for E2, we obtain E4 \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \left( \infty \sum j=k0 2(k - j)(n\delta 1+\alpha (0)+\lambda )q/22j\alpha (0)q\| fj\| qLp(\cdot )(\BbbR n) \right) \times \times \left( \infty \sum j=k0 (j - k)q \prime 2(k - j)(n\delta 1+\alpha (0) - \lambda )q\prime /2 \right) q/q\prime \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty \left( \infty \sum j=k0 2(k - j)(n\delta 1+\alpha (0)+\lambda )q/22j\lambda q2 - j\lambda q j\sum l= - \infty 2l\alpha (0)q\| fl\| qLp(\cdot )(\BbbR n) \right) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q k0\sum k= - \infty 2k\lambda q \left( \infty \sum j=k0 2(k - j)(n\delta 1+\alpha (0) - \lambda )q/2 \right) \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) \lesssim \lesssim \mathrm{s}\mathrm{u}\mathrm{p} k0<0,k0\in \BbbZ 2 - k0\lambda q \Biggl( k0\sum k= - \infty 2k\lambda q \Biggr) \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) \lesssim \| f\| q M \.K \alpha (\cdot ),\lambda q,p(\cdot ) (\BbbR n) . 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Received 06.06.17, after revision — 29.10.18 ISSN 1027-3190. Укр. мат. журн., 2020, т. 72, № 7
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spelling umjimathkievua-article-60232022-03-26T11:01:57Z On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces Qu, M. Wang, L. Qu, M. Wang, L. UDC 517.5 In the framework of variable exponent Morrey and Morrey–Herz spaces, we prove some boundedness results for the commutator of Marcinkiewicz integrals with rough kernels. The approach is based on the theory of variable exponent and on generalization of the BMO-norms. УДК 517.5 Про комутатор iнтегралiв Марцинкевича з грубими ядрами у змiнних просторах типу Моррея У рамках змiнних експонент просторiв Морi та Морi–Герца доведено деякi результати стосовно обмеженостi комутатора iнтегралiв Марцинкевича з грубими ядрами. Цей пiдхiд базується на теорiї змiнних експонент та узагальненнi норм обмежених усереднених осциляцiй. Institute of Mathematics, NAS of Ukraine 2020-07-15 Article Article application/pdf https://umj.imath.kiev.ua/index.php/umj/article/view/6023 10.37863/umzh.v72i7.6023 Ukrains’kyi Matematychnyi Zhurnal; Vol. 72 No. 7 (2020); 928-944 Український математичний журнал; Том 72 № 7 (2020); 928-944 1027-3190 en https://umj.imath.kiev.ua/index.php/umj/article/view/6023/8729
spellingShingle Qu, M.
Wang, L.
Qu, M.
Wang, L.
On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces
title On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces
title_alt On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces
title_full On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces
title_fullStr On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces
title_full_unstemmed On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces
title_short On the commutator of Marcinkiewicz integrals with rough kernels in variable Morrey type spaces
title_sort on the commutator of marcinkiewicz integrals with rough kernels in variable morrey type spaces
url https://umj.imath.kiev.ua/index.php/umj/article/view/6023
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