Open Journal of Mathematical Sciences
ISSN: 2523-0212 (Online) 2616-4906 (Print)
DOI: 10.30538/oms2019.0052
Boundedness of commutators on herz-morry-hardy spaces with variable exponent
Omer Abdalrhman\(^1\), Afif Abdalmonem, Shuangping Tao
College of Mathematics and Statistics, Northwest Normal University, Lanzhou, Gansu, P.R. China.;(O.A & A.A & S.T)
College of Education, Shendi University, Shendi, River Nile State, Sudan.; (O.A)
Faculty of Science, University of Dalanj, Dalanj, South kordofan, Sudan. (A.A)
\(^{1}\)Corresponding Author: humoora@gmail.com
Abstract
Keywords:
1. Introduction
Suppose \( \mathbb{S}^{n-1}, (n\geq 2)\) denote the unit sphere in \( \mathbb{R}^{n}\) equipped with the normalized Lebesgue measure \( \mathrm{d}\sigma=\mathrm{d}(\sigma^{\prime})\) . Let \( \Omega\) be homogeneous function of degree zero and satisfiesDefinition 1. Let \( \Omega\subset\mathbb{R}^{n}\) be a subset of \( \mathbb{R}^{n}\) with the Lebesgue measure \( >0.\) For a measurable function \( p(\cdot):\Omega\rightarrow[1,\infty)\) , the variable Lebesgue space is defined as $$ L^{p(\cdot)}(\Omega):=\left\{h \text{is measurable on} \Omega:\rho_{p}(h) < \infty\right\},$$ where $$ \rho_{p}(h):=\int_{\Omega}\left(\frac{|h(x)|}{\mu}\right)^{p(x)}dx < \infty \text{for some constat} \mu>0.$$ The set \( L^{p(\cdot)}(\Omega)\) is a quasi Banach space with following Luxemburg-Nakano norm $$ \|h\|_{L^{p(\cdot)}}:=\inf\left\{\mu>0 : \rho_{p}(\mu^{-1} h)\leq1\right\}.$$ The space \( L_{\mathrm{loc}}^{p(\cdot)}(\Omega)\) is defined as $$ L_{\mathrm{loc}}^{p(\cdot)}(\Omega):=\left\{h: h\chi_{k}\in L^{p(\cdot)}(\mathbb{R}^{n}) \text{for any compact subset} K\subset\Omega\right\}.$$ Suppose \( \mathcal{P}(\Omega)\) represents the set of all function \( p:\Omega\rightarrow[1,\infty)\) . Assume that \( p_{-}=\text{ess}\inf_{x\in\Omega} p(x)\) and \( p_{+}=\text{ess}\sup_{x\in\Omega} p(x)\) . Set \( p_{-}>1 \text{,} p_{+}< \infty\) and \( p(\cdot), p'(\cdot)\) are conjugate exponent function defined by \( 1/p(\cdot)+1/p'(\cdot)=1.\) Let \( \mathcal{B}(\Omega)\) be the set of \( p(\cdot)\in\mathcal{P}(\Omega)\) satisfying that the maximal function is bounded on \( L^{p(\cdot)}\) .
Definition 2. (see[11]. Let \( p(\cdot)\in \mathcal{P}(\mathbb{R}^{n}), 0< q< \infty, 0\leq \lambda < \infty, \alpha(\cdot)\in L^{\infty}(\mathbb{R}^{n})\) and \( N>n+1\) . The homogeneous Herz-Morrey-Hardy spaces \( HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})\) and nonhomogeneous Herz-Morrey-Hardy spaces \( HMK^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})\) are defined as $$ HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})=\left\{h\in\mathcal{S^{\prime}}(\mathbb{R}^{n}): \|h\|_{HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})} :=\|G_{N}h\|_{M\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})}< \infty\right\},$$ $$ HMK^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})=\left\{h\in\mathcal{S^{\prime}}(\mathbb{R}^{n}):\|h\|_{HMK^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})} :=\|G_{N}h\|_{M\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})}< \infty\right\}.$$ respectively.
2. Preliminaries and Lemmas
Proposition 3. (see[14]. Given a function \( p(\cdot): \mathbb{R}^{n} \rightarrow [ 1 , \infty).\) If \( p(\cdot)\in \mathcal{P}(\mathbb{R}^{n})\) satisfies
Lemma 4. (see[5]). (Generalized Hölder's Inequality) Given \( p(\cdot), p_{1}(\cdot), p_{2}(\cdot)\in\mathcal{P}(\mathbb{R}^{n})\) .
- For every \( h\in L^{p_{1}(\cdot)}(\mathbb{R}^{n}) \text{and} g\in L^{p_{2}(\cdot)}(\mathbb{R}^{n})\) , we have $$ \int_{\mathbb{R}^{n}}|h(x) g(x)| dx \leq C\|h\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\|g\|_{L^{p'(\cdot)}(\mathbb{R}^{n})},$$ where \( C_{p}=1+\frac{1}{p_{-}}-\frac{1}{p_{+}}\) .
- For every \( h\in L^{p_{1}(\cdot)}(\mathbb{R}^{n}),\) and \( g\in L^{p_{2}(\cdot)}(\mathbb{R}^{n})\) , when \( \frac{1}{p(\cdot)}=\frac{1}{p_{2}(\cdot)}+\frac{1}{p_{1}(\cdot)}\) , we have $$ \|h(x)g(x)\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\leq C \|g(x)\|_{L^{p_{2}}(\mathbb{R}^{n})}\|h(x)\|_{L^{p_{1}(\cdot)}(\mathbb{R}^{n})},$$ where \( C_{p_{1},p_{2}}=[1+\frac{1}{p_{1-}}-\frac{1}{p_{1+}}]^{\frac{1}{p_{-}}}\) .
Lemma 5. (see[15, 16]). Given \( p(\cdot) \in \mathcal{B}(\mathbb{R}^{n})\) . If there exist positive constants \( C,\) \( \delta_{1}\) and \( \delta_{2}\) such that \( \delta_{1}, \delta_{2}< 1\) , then for all balls \( B\subset\mathbb{R}^{n}\) and all measurable subset \( R\subset B,\) we have $$ \frac{\|\chi_{R}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}}{\|\chi_{B}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}}\leq C \frac{|R|}{|B|}, \frac{\|\chi_{R}\|_{L^{p^{\prime}(\cdot)}(\mathbb{R}^{n})}}{\|\chi_{B}\|_{L^{p^{\prime}(\cdot)}(\mathbb{R}^{n})}}\leq C\left(\frac{|R|}{|B|}\right)^{\delta_{2}}, \frac{\|\chi_{R}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}}{ \|\chi_{B}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}}\leq C\left(\frac{|R|}{|B|}\right)^{\delta_{1}}.$$
Lemma 6. (see[17]). If \( p(\cdot) \in \mathcal{B}(\mathbb{R}^{n}),\) then there exists a constant \( C > 0\) such that for any ball \( B\) in \( \mathbb{R}^{n}\) , we have $$ \frac{1}{|B|}\|\chi_{B}\|_{L^{p(\cdot)}(\mathbb{R}^{n})} \|\chi_{B}\|_{L^{p'(\cdot)}(\mathbb{R}^{n})}\leq C. $$ Now, the BMO function and BMO norm are defined as \begin{align*} \mathrm{BMO}(\mathbb{R}^{n})&:=\left\{b\in L^{1}_{loc}(\mathbb{R}^{n}):\|b\|_{\mathrm{BMO}(\mathbb{R}^{n})}< 0\right\},\\ \|b\|_{\mathrm{BMO}(\mathbb{R}^{n})}&:=\sup\limits_{Q:\text{cube}}|Q|^{-1}\int_{Q}|b(x)-b_{Q}|\text{d}x. \end{align*} respectively.
Lemma 7. (see[18]). Given \( p(\cdot) \in \mathcal{B}(\mathbb{R}^{n}), b\in \mathrm{BMO}(\mathbb{R}^{n})\) . If \( i,j\in\mathbb{Z}\) with \( i< j\) , then we have
- \( C^{-1}\|b\|_{\mathrm{BMO}(\mathbb{R}^{n})} \leq\sup\limits_{B}\frac{1}{\|\chi_{B}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}}\|(b-b_{B})\chi_{B}\|_{L^{p(\cdot)}(\mathbb{R}^{n})} \leq C\|b\|_{\mathrm{BMO}(\mathbb{R}^{n})}.\)
- \( \|(b-b_{B_{i}})\chi_{B_{j}}\|_{L^{q(\cdot)}(\mathbb{R}^{n})}\leq C( j-i)\|b\|_{\mathrm{BMO}(\mathbb{R}^{n})}\|\chi_{B_{j}}\|_{L^{q(\cdot)}(\mathbb{R}^{n})}.\)
Lemma 8. (see[18]). Suppose that \( p(\cdot)\in\mathcal{P}(\mathbb{R}^{n}), q\in[0,\infty)\) and \( \lambda\in[0,\infty)\) . If \( \alpha(\cdot)\) is log-Hölder's continuous both at origin and at infinity, then \begin{eqnarray*} &&\qquad\|h\|_{M\dot{K}_{p(\cdot),\lambda}^{\alpha(\cdot),q}(\mathbb{R}^{n})}\approx max \left\{{\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda } \left(\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q} \left\|h\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q}}, \right.\\ &&\left. \sup\limits_{L>0,L\in \mathbb{Z}} \left[2^{-L\lambda } \left(\sum\limits_{k=-\infty}^{-1} 2^{k\alpha(0)q}\left\|h\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q} + 2^{-L\lambda }\left( \sum\limits_{k=0}^{L}2^{k\alpha_{\infty}q} \left\|h\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q}\right]\right\}. \end{eqnarray*}
Lemma 9. (see[4]). Let \( \Omega\) satisfies \( L^{r}\) -Dini condition \( r\in[1,\infty)\) . If there exist constants \( C>0\) and \( R>0\) such that \( |y|< R/2\) , then for every \( x\in\mathbb{R}^{n}\) , we have $$ \left(\int_{R< |x|< 2R}\left|\frac{\Omega(x-y)}{|x-y|^{n}}-\frac{\Omega(x)}{|x|^{n}}\right|^{r}dx\right)^{\frac{1}{r}} \leq CR^{(\frac{n}{r}-n)}\left\{\frac{|y|}{R}+\int_{|y|/2R< \delta< |y|/R}\frac{w_{r}(\delta)}{\delta}d\delta\right\}.$$
Lemma 10. (see[11]). Suppose that \( p(\cdot)\in\mathcal{B}(\mathbb{R}^{n}), q\in[0,\infty)\) and \( \lambda\in[0,\infty)\) . Let \( \alpha(\cdot)\) is log-Hölder's continuous both at origin and at infinity. If \( 2\lambda\leq \alpha(\cdot), n\delta_{2}\leq \alpha(0), \alpha< \infty \text{and} \delta_{2}\) as defined in Lemma \ref{l2.2}. Then \( h\in HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n}) \left(\text{or} HM{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}(\mathbb{R}^{n})\right)\) if and only if \( h=\sum\limits_{k=-\infty}^{\infty}\lambda_{k}g_{k} \left(\text{or} \sum\limits_{k=0}^{\infty}\lambda_{k}g_{k}\right)\) , in the sense of \( \mathcal{S}'(\mathbb{R}^{n})\) , where each \( g_{k}\) be a central \( (\alpha(\cdot),p(\cdot))\) -atom (or central \( (\alpha(\cdot), p(\cdot))\) -atom of restricted type) with support contained in \( B_{k}\) and \( \sup\limits_{L\in\mathbb{Z}} 2^{-L\lambda}\sum\limits_{k=-\infty}^{L}|\lambda_{k}|^{q} < \infty\) or \( \left(\sup\limits_{L\in\mathbb{Z}} 2^{-L\lambda}\sum\limits_{k=0}^{L}|\lambda_{k}|^{q}< \infty\right).\) \\ Also,\\ \( \|h\|_{HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}}\approx\inf\sup\limits_{L\in\mathbb{Z}} 2^{L\lambda} \left(\sum\limits_{k=-\infty}^{L}|\lambda_{k}|^{q}\right)^{1/q}\left(\text{or} \|h\|_{HM{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}}\approx\inf\sup\limits_{L\in\mathbb{Z}} 2^{L\lambda} \left(\sum\limits_{k=0}^{L}|\lambda_{k}|^{q}\right)^{1/q}\right),\) \\ where infimum is taken over all above decomposition of \( h\) .
Lemma 11(see [19]). Let \( p(\cdot)\in \mathcal{P}(\Omega)\) and \( h:\Omega\times \Omega\rightarrow \mathbb{R}\) is a measurable function (with respect to product measure) such that, for almost every \( y\in \Omega, h(\cdot,y)\in L^{p(\cdot)}(\Omega)\) . Then $$ \left\|\int_{\Omega}h(\cdot,y)dy\right\|_{L^{p(\cdot)}(\Omega)}\leq C \int_{\Omega}\left\|h(\cdot,y)\right\|_{L^{p(\cdot)}(\Omega)}dy.$$
Lemma 12. (see[19]). Suppose \( p(\cdot)\in \mathcal{P}(\mathbb{R}^{n})\) satisfies conditions \eqref{2.1} and \eqref{2.2} of Proposition \ref{p2.1}, then for any ball (or cube) \( Q\subset\mathbb{R}^{n}\) , we have $$ {\|\chi_{Q}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}}\approx\left\{\begin{array}{ll} |Q|^{\frac{1}{p(x)}}, \text{if} |Q|\leq 2^{n};\\ |Q|^{\frac{1}{p(\infty)}}, \text{if} |Q|\geq 1, \end{array}\right.$$ where \( p(\infty)=\lim\limits_{x\rightarrow\infty}p(x).\)
3. Main Results
In this section, we formulate and prove the main results of this paper.Theorem 13. Let \( p(\cdot)\in \mathcal{B}(\mathbb{R}^{n}) \text{and} \Omega\in L^{r}(\mathbb{S}^{n-1})(r>p^{+})\) satisfies
Proof.
It suffices to prove for \(
HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}\)
. Assume that \(
h\in HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}\)
, then by Lemma 10,
\(
h=\sum\limits_{j=-\infty}^{\infty}\lambda_{j}g_{j}\)
converges in \(
\mathcal{S}'(\mathbb{R}^{n}),\)
where \(
\|h\|_{HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}}\approx\inf\sup\limits_{L\in\mathbb{Z}} 2^{L\lambda}
(\sum\limits_{j=-\infty}^{L}|\lambda_{j}|^{q})^{1/q},\)
and \(
g_{j}\)
is a dyadic central \(
(\alpha(\cdot),p(\cdot))\)
-atom with support contained in \(
B_{j}\)
. For simplicity, we take \(
\Upsilon=\sup\limits_{L\in\mathbb{Z}} 2^{L\lambda}\sum\limits_{j=-\infty}^{L}|\lambda_{j}|^{q}.\)
By virtue of Lemma 8, we have
\begin{eqnarray*}
&&\|T_{\Omega}(h)\|_{M\dot{K}_{p(\cdot),\lambda}^{\alpha(\cdot),q}(\mathbb{R}^{n})}\approx max \left\{{\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda }
\left(\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q} \left\|T_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q}},
\right.\\
&&\left.
\sup\limits_{L>0,L\in \mathbb{Z}} \left[2^{-L\lambda } \left(\sum\limits_{k=-\infty}^{-1}
2^{k\alpha(0)q}\left\|T_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q} + 2^{-L\lambda }\left( \sum\limits_{k=0}^{L}2^{k\alpha_{\infty}q}
\left\|T_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q}\right]\right\}\\
&&\approx max \left\{E,F+G\right\}.
\end{eqnarray*}
Let
\begin{eqnarray*}
E&=&\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left\|T_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})},\\
F&=&\sum\limits_{k=-\infty}^{-1}2^{k\alpha(0)q}\left\|T_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})},\\
G&=&\sup\limits_{L>0,L\in \mathbb{Z}}2^{-L\lambda q}\sum\limits_{k=0}^{L}2^{k\alpha_{\infty}q}
\left\|T_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}.
\end{eqnarray*}
To finish our proof, we only need to show that there exists a constant \(
C>0\)
, such that \(
E, F \text{,} G\leq C\Upsilon.\)
First we prove that \(
E\leq C\Upsilon\)
.
\begin{eqnarray*}
E&=&\sup\limits_{L\leq0,L\in \mathbb{Z}}
2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left\|T_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\leq \sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=k}^{\infty}|\lambda_{j}|
\|T_{\Omega}g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{q}\\
&& +\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=-\infty}^{k-1}|\lambda_{j}|
\|T_{\Omega}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{q}:=E_{1}+E_{2}.
\end{eqnarray*}
By the \(
\left(L^{p(\cdot)}(\mathbb{R}^{n}),L^{p(\cdot)}(\mathbb{R}^{n})\right)\)
-boundedness of the \(
T_{\Omega}\)
(see[13]), we get
$$
\|T_{\Omega}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\leq \|g_{j}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\leq |B_{j}|^{-\alpha_{j}/n}=2^{-j\alpha_{j}}.$$
Therefore, when \(
0< q\leq1,\)
we obtain
\begin{eqnarray*}
E_{1}&=&\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=k}^{\infty}|\lambda_{j}|
\|T_{\Omega}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{q}\\
&\leq& C \sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=k}^{\infty}|\lambda_{j}|
2^{-j\alpha_{j}}\right)^{q}\\
&\leq& C \sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left[\left(\sum\limits_{j=k}^{-1}|\lambda_{j}|
2^{-j\alpha(0)}+\sum\limits_{j=0}^{\infty}|\lambda_{j}|2^{-j\alpha_{\infty}}\right)^{q}\right]\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}\sum\limits_{j=k}^{-1}|\lambda_{j}|^{q}
2^{(k-j)\alpha(0)q}\right.\left.+\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\left(
\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)}\sum\limits_{j=0}^{\infty}|\lambda_{j}|2^{-j\alpha_{\infty}}
\right)^{q}\right]\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}}
2^{-L\lambda q}\sum\limits_{j=-\infty}^{-1}|\lambda_{j}|^{q}\sum\limits_{k=-\infty}^{j}
2^{(k-j)\alpha(0)q}\right.\left.+\sup\limits_{L\leq0,L\in \mathbb{Z}}
\sum\limits_{j=0}^{\infty}2^{-j\lambda q} |\lambda_{j}|^{q}2^{(\lambda-\alpha_{\infty})jq}2^{-L\lambda q}\sum\limits_{k=\infty}^{L}2^{k\alpha(0)q}\right]\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}}2^{-L\lambda q}\sum\limits_{j=-\infty}^{L}|\lambda_{j}|^{q}
+\sup\limits_{L\leq0,L\in \mathbb{Z}}2^{-L\lambda q}\sum\limits_{j=L}^{-1}|\lambda_{j}|^{q}\sum\limits_{k=-\infty}^{j}2^{(k-j)\alpha(0)q}\right.\\
&& +\left.\Upsilon\sup\limits_{L\leq0,L\in \mathbb{Z}}\sum\limits_{j=0}^{\infty}2^{(\lambda-\alpha_{\infty})jq}\sum\limits_{k=\infty}^{L}2^{[k\alpha(0)-L\lambda]q}\right]\\
&\leq& C \left[\Upsilon+\sup\limits_{L\leq0,L\in \mathbb{Z}}\sum\limits_{j=L}^{-1}2^{-j\lambda q}|\lambda_{j}|^{q}2^{(j-L)\lambda q}\sum\limits_{k=-\infty}^{j}2^{(k-j)\alpha(0)q}+\Upsilon\right]\\
&\leq& C \left[\Upsilon+\Upsilon\sup\limits_{L\leq0,L\in \mathbb{Z}}\sum\limits_{j=L}^{-1}2^{(j-L)\lambda q}\sum\limits_{k=-\infty}^{j}2^{(k-j)\alpha(0)q}+\Upsilon\right]\leq C \Upsilon.
\end{eqnarray*}
when \(
1< q< \infty\)
, and \(
1/q+1/q^{\prime}=1\)
, we have
\begin{eqnarray*}
E_{1}&=&\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=k}^{\infty}|\lambda_{j}|
\|T_{\Omega}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{q}\\
&\leq& C \sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=k}^{\infty}|\lambda_{j}|
2^{-j\alpha_{j}}\right)^{q}\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}\left(\sum\limits_{j=k}^{-1}|\lambda_{j}|
2^{(k-j)\alpha(0)}\right)^{q}\right.\left.+\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=0}^{\infty}|\lambda_{j}|2^{-j\alpha_{\infty}}
\right)^{q}\right]\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}\left(\sum\limits_{j=k}^{-1}|\lambda_{j}|^{q}
2^{(k-j)\alpha(0){\frac{q}{2}}}\right)\times\left(\sum\limits_{j=k}^{-1}
2^{(k-j)\alpha(0){\frac{q^{\prime}}{2}}}\right)^{\frac{q}{q^{\prime}}}\right.\\
&& \left.+\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=0}^{\infty}
|\lambda_{j}|^{q}2^{-j\alpha_{\infty}\frac{q}{2}}\right)
\times\left(\sum\limits_{j=0}^{\infty}2^{-j\alpha_{\infty}\frac{q^{\prime}}{2}}
\right)^{\frac{q}{q^{\prime}}}\right]\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}\sum\limits_{j=k}^{-1}|\lambda_{j}|^{q}
2^{(k-j)\alpha(0){\frac{q}{2}}}\right.\left.+\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\sum\limits_{j=0}^{\infty}|\lambda_{j}|^{q}
2^{-j\alpha_{\infty}\frac{q}{2}}\right]\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{j=-\infty}^{-1}|\lambda_{j}|^{q}\sum\limits_{k=\infty}^{j}
2^{(k-j)\alpha(0){\frac{q}{2}}}\right.\left.+\sup\limits_{L\leq0,L\in \mathbb{Z}}\sum\limits_{j=0}^{\infty}2^{-j\lambda q}|\lambda_{j}|^{q} 2^{(\lambda-\frac{\alpha_{\infty}}{2})jq}2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\right]\\
&\leq& C \left[\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{j=-\infty}^{L}|\lambda_{j}|^{q}
+\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{j=L}^{-1}|\lambda_{j}|^{q}\sum\limits_{k=\infty}^{j}
2^{(k-j)\alpha(0){\frac{q}{2}}}\right.\\
&& \left.+\Upsilon\sup\limits_{L\leq0,L\in \mathbb{Z}}\sum\limits_{j=0}^{\infty} 2^{(\lambda-\frac{\alpha_{\infty}}{2})jq}2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\right]
\end{eqnarray*}
\begin{eqnarray}\label{3.1}
&&\leq C \left[\Upsilon+\sup\limits_{L\leq0,L\in \mathbb{Z}} \sum\limits_{j=L}^{-1}2^{-j\lambda q}|\lambda_{j}|^{q}2^{(j-L)\lambda q}\sum\limits_{k=\infty}^{j}
2^{(k-j)\alpha(0){\frac{q}{2}}}+\Upsilon\right]\nonumber\\
&&\leq C \left[\Upsilon+\Upsilon\sup\limits_{L\leq0,L\in \mathbb{Z}} \sum\limits_{j=L}^{-1}2^{(j-L)\lambda q}\sum\limits_{k=\infty}^{j}
2^{(k-j)\alpha(0){\frac{q}{2}}}+\Upsilon\right]\nonumber\\
&&\leq C \Upsilon.
\end{eqnarray}
Now, we prove that \(
E_{2}\leq C\Upsilon\)
. Note that if \(
x\in A_{k} \text{for each} k\in\mathbb{Z},y\in A_{j}\)
and \(
j\leq k-1\)
. Let \(
\tilde{p}(\cdot)>1 \text{and} 1/p(\cdot)=1/\tilde{p}(\cdot)+1/r\)
. Since \(
r>p^{+}\)
, so by Lemma 4 and Lemma 11, we get
Theorem 14. Suppose that \( b\in \mathrm{BMO}(\mathbb{R}^{n}), p(\cdot)\in \mathcal{B}(\mathbb{R}^{n})\) and let \(\Omega\in L^{r}(\mathbb{S}^{n-1})(r>p^{+})\) satisfies (7). Let \( 0< q< \infty, 0\leq\lambda< \infty \text{and} \alpha(\cdot)\in L^{\infty}(\mathbb{R}^{n})\) satisfies conditions (4) and (5) of Proposition 3. If \( 2\lambda\leq\alpha(\cdot), n\delta_{2}\leq \alpha(0),\alpha_{\infty}< \beta+n\delta_{2},\) then \( [b,T_{\Omega}]\) is bounded from \( HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}\) or \( \left(HMK^{\alpha(\cdot),q}_{p(\cdot),\lambda}\right)\) to \( M\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}\) or \( \left(MK^{\alpha(\cdot),q}_{p(\cdot),\lambda}\right).\)
Proof.
It suffices to prove for \(
HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}\)
. Set \(
b\in \mathrm{BMO}(\mathbb{R}^{n})\)
and \(
h\in HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}\)
. By Lemma 10, \(
h=\sum\limits_{j=-\infty}^{\infty}\lambda_{j}g_{j}\)
converges in \(
\mathcal{S}'(\mathbb{R}^{n}),\)
where \(
\|h\|_{HM\dot{K}^{\alpha(\cdot),q}_{p(\cdot),\lambda}}\approx\inf\sup\limits_{L\in\mathbb{Z}} 2^{L\lambda}
\left(\sum\limits_{j=-\infty}^{L}|\lambda_{j}|^{q}\right)^{1/q},\)
and \(
g_{j}\)
is a dyadic central \(
(\alpha(\cdot),p(\cdot))\)
-atom with support contained in \(
B_{j}\)
. For simplicity, we denote \(
\Upsilon=\sup\limits_{L\in\mathbb{Z}} 2^{L\lambda}\sum\limits_{j=-\infty}^{L}|\lambda_{j}|^{q}.\)
By virtue of Lemma 8, we rewrite
$$
\begin{array}{ll}
\|T^{b}_{\Omega}(h)\|_{M\dot{K}_{p(\cdot),\lambda}^{\alpha(\cdot),q}(\mathbb{R}^{n})} \approx max \left\{{\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda }
\left(\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q} \left\|T^{b}_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q}},
\right.\\
\\
\left.
\sup\limits_{L>0,L\in \mathbb{Z}} \left[2^{-L\lambda } \left(\sum\limits_{k=-\infty}^{-1}
2^{k\alpha(0)q}\left\|T^{b}_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q} + 2^{-L\lambda }\left( \sum\limits_{k=0}^{L}2^{k\alpha_{\infty}q}
\left\|T^{b}_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{1/q}\right]\right\}\\ \approx max \left\{E',F'+G'\right\}
\end{array}$$
where
\begin{eqnarray*}
&E'&=\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left\|T^{b}_{\Omega}(h)\chi_{k}
\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})},\\
&F'&=\sum\limits_{k=-\infty}^{-1}
2^{k\alpha(0)q}\left\|T^{b}_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})},\\
&G'&=\sup\limits_{L>0,L\in \mathbb{Z}}2^{-L\lambda q}\sum\limits_{k=0}^{L}2^{k\alpha_{\infty}q}
\left\|T^{b}_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}.
\end{eqnarray*}
To complete the prove, we only need to show that there exists a constant \(
C>0\)
, such that \(
E',F' \text{,} G'\leq C\Upsilon.\)
First we show that \(
E'\leq C\Upsilon.\)
\begin{eqnarray*}
&E'&=\sup\limits_{L\leq0,L\in \mathbb{Z}}
2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left\|T^{b}_{\Omega}(h)\chi_{k}\right\|^{q}_{L^{p(\cdot)}(\mathbb{R}^{n})}\\
&&\leq \sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=k}^{\infty}|\lambda_{j}|
\|T^{b}_{\Omega}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{q}\\
&& +\sup\limits_{L\leq0,L\in \mathbb{Z}} 2^{-L\lambda q}\sum\limits_{k=-\infty}^{L}2^{k\alpha(0)q}\left(\sum\limits_{j=-\infty}^{k-1}|\lambda_{j}|
\|T^{b}_{\Omega}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}\right)^{q}\\
&&:=E'_{1}+E'_{2}.
\end{eqnarray*}
By the \(
\left(L^{p(\cdot)}(\mathbb{R}^{n}),L^{p(\cdot)}(\mathbb{R}^{n})\right)\)
-boundedness of the \(
T^{b}_{\Omega}\)
(see [13]) and following the same way as we estimated \(
E_{1}\)
in Theorem 13, we get
\(
E'_{1}\leq C \|b\|_{\ast}\Upsilon.\)
Now, we estimate \(
E'_{2}\)
. For each \(
k\in \mathbb{Z}\)
and \(
x\in A_{k}\)
, by Lemma 7 and Minkowski inequality, we get
\begin{eqnarray*}
\|T_{\Omega}^{b}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}
&\leq&
\int_{B_{j}}\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}
\right|(b(\cdot)-b(y))\chi_{k}
\right\|_{L^{p(\cdot)}(\mathbb{R}^{n})}|g_{j}(y)|\mathrm{d}y\\
&\leq&\int_{B_{j}}\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}
\right||b(\cdot)-b_{B_{j}}|\chi_{k}
\right\|_{L^{p(\cdot)}(\mathbb{R}^{n})}|g_{j}(y)|\mathrm{d}y\\
&&+\int_{B_{j}}\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}
\right|\chi_{k}\right\|_{L^{p(\cdot)}(\mathbb{R}^{n})}|b_{B_{j}}-b(y)||g_{j}(y)|\mathrm{d}y.
\end{eqnarray*}
Since \(
\tilde{p}(\cdot)>1 \text{and} 1/p(\cdot)=1/\tilde{p}(\cdot)+1/r\)
. Since \(
r>p^{+}\)
, so by Lemma 4 and Lemma 11, we get
\begin{eqnarray*}
\|T_{\Omega}^{b}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}
&\leq& \left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}\right|
\right\|_{L^{r}(\mathbb{R}^{n})}\left\|b(\cdot)-b_{B_{j}}\chi_{k}
\right\|_{L^{\tilde{p}(\cdot)}(\mathbb{R}^{n})}\int_{B_{j}}|g_{j}(y)|dy\\
&&+\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}
\right|\right\|_{L^{r}(\mathbb{R}^{n})}
\|\chi_{B_{k}}\|_{L^{\tilde{p}(\cdot)}(\mathbb{R}^{n})}\int_{B_{j}}|b_{B_{j}}-b(y)||g_{j}(y)|dy
\end{eqnarray*}
From (8) and Lemmas 4-6, we get
Theorem 15. Suppose that \(b\in \dot{\Lambda}_{\gamma}(\mathbb{R}^{n})(0< \gamma\leq 1), p_{1}(\cdot), p_{2}(\cdot)\in \mathcal{B}(\mathbb{R}^{n})\) be such that \( p_{1}^{+}< n/\gamma, 1/p_{1}(x)-1/p_{2}(x)=\gamma/n, \Omega\in L^{r}(\mathbb{S}^{n-1})(r>q^{+}_{2})\) with \( 1\leq r' < p_{1}^{-}\) and satisfies $$ \int^{1}_{0}\frac{w_{r}(\delta)}{\delta^{1+\gamma}}d\delta < \infty.$$ Let \( 0< q< \infty, 0\leq\lambda< \infty \text{and} \alpha(\cdot)\in L^{\infty}(\mathbb{R}^{n})\) satisfies conditions (4) and (5) of Proposition 3. If \( 2\lambda\leq\alpha(\cdot), n\delta_{2}\leq \alpha(0),\alpha_{\infty}< \gamma+n\delta_{2},\) then \( [b,T_{\Omega}]\) is bounded from \( HM\dot{K}^{\alpha(\cdot),q}_{p_{1}(\cdot),\lambda}\) or \( \left(HMK^{\alpha(\cdot),q}_{p_{1}(\cdot),\lambda}\right)\) to \( M\dot{K}^{\alpha(\cdot),q}_{p_{2}(\cdot),\lambda}\) or \( \left(MK^{\alpha(\cdot),q}_{p_{2}(\cdot),\lambda}\right).\)
Proof. The prove of this Theorem follows almost similarly to that of Theorem 14. Instead of giving all details, we only give the modifications required for the estimation of \( E'', F'' \text{and} G''\) . Note that if \( x\in B_{k} \text{for each} k\in\mathbb{Z}, y\in B_{j}\) and \( j\leq k-1\) . Let \( \tilde{p}(\cdot)>1 \text{and} 1/p(\cdot)=1/\tilde{p}(\cdot)+1/r\) , since \( r>p^{+}\) , so by Lemmas 10 and 12, we get \begin{eqnarray*} \|T_{\Omega}^{b}(g_{j})\chi_{k}\|_{L^{p(\cdot)}(\mathbb{R}^{n})}&\leq& \int_{B_{j}}\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}} \right|(b(\cdot)-b(y))\chi_{k}\right\|_{L^{p_{2}(\cdot)}(\mathbb{R}^{n})}|g_{j}(y)|dy\\ &\leq& \int_{B_{j}}\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}} \right||b(\cdot)-b_{B_{j}}|\chi_{k}\right\|_{L^{p_{2}(\cdot)}(\mathbb{R}^{n})}|g_{j}(y)|dy\\ && +\int_{B_{j}}\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}\right|\chi_{k} \right\|_{L^{p_{2}(\cdot)}(\mathbb{R}^{n})}|b_{B_{j}}-b(y)||g_{j}(y)|dy \end{eqnarray*} Since \( \tilde{p_{2}}(\cdot)>1 \text{and} 1/p_{2}(\cdot)=1/\tilde{p_{2}}(\cdot)+1/r\) , by \( r>p^{+}\) and Lemmas 11 and 12, we deduced \begin{eqnarray*} \|T_{\Omega}^{b}(g_{j})\chi_{k}\|_{L^{p_{2}(\cdot)}(\mathbb{R}^{n})}&\leq& \left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}\right| \right\|_{L^{r}(\mathbb{R}^{n})}\left\|(b-b_{B_{j}})\chi_{k} \right\|_{L^{\tilde{p}_{2}(\cdot)}(\mathbb{R}^{n})}\int_{B_{j}}|g_{j}(y)|dy\\ && +\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}\right|\right\|_{L^{r}(\mathbb{R}^{n})} \|\chi_{B_{k}}\|_{L^{\tilde{p}_{2}(\cdot)}(\mathbb{R}^{n})}\int_{B_{j}}|b_{B_{j}}-b(y)||g_{j}(y)|dy\\ &\leq& C \left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}\right| \right\|_{L^{r}(\mathbb{R}^{n})}\left\|(b-b_{B_{j}})\chi_{k} \right\|_{L^{\tilde{p}_{2}(\cdot)}(\mathbb{R}^{n})}\|g_{j}\|_{L^{p_{1}(\cdot)}(\mathbb{R}^{n})} \|\chi_{j}\|_{L^{p'_{1}(\cdot)}(\mathbb{R}^{n})}\\ && +\left\|\left|\frac{\Omega(\cdot-y)}{|\cdot-y|^{n}}-\frac{\Omega(\cdot)}{|\cdot|^{n}}\right| \right\|_{L^{r}(\mathbb{R}^{n})}\|\chi_{B_{k}}\|_{L^{\tilde{p}_{2}(\cdot)}(\mathbb{R}^{n})} \|(b-b_{B_{j}})\chi_{B_{j}}\|_{L^{p'_{1}(\cdot)}(\mathbb{R}^{n})} \|g_{j}\|_{L^{p_{1}(\cdot)}(\mathbb{R}^{n})}. \end{eqnarray*} By Lemma 9, we have
Acknowledgments
This paper is supported by Shendi University.Authorcontributions
All authors contributed equally to the writing of this paper. All authors read and approved the final manuscript.Competing Interests
The author(s) do not have any competing interests in the manuscript.References
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