<p>In this paper, we investigate the bilinear Stein’s square functions associated with the bilinear Bochner-Riesz means, defined as <Equation ID="Equ1"> <EquationSource Format="TEX">\( \mathcal {G}^\alpha (f, g)(x):=\left( \int _0^{\infty }\left| \frac{\partial }{\partial R} \mathcal {B}_R^{\alpha +1}(f, g)(x)\right| ^2 R d R\right) ^{\frac{1}{2}}, \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msup> <mrow> <mi mathvariant="script">G</mi> </mrow> <mi>α</mi> </msup> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo>,</mo> <mi>g</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>:</mo> <mo>=</mo> <msup> <mfenced close=")" open="("> <msubsup> <mo>∫</mo> <mn>0</mn> <mi>∞</mi> </msubsup> <msup> <mfenced close="|" open="|"> <mfrac> <mi>∂</mi> <mrow> <mi>∂</mi> <mi>R</mi> </mrow> </mfrac> <msubsup> <mi mathvariant="script">B</mi> <mi>R</mi> <mrow> <mi>α</mi> <mo>+</mo> <mn>1</mn> </mrow> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo>,</mo> <mi>g</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> </mfenced> <mn>2</mn> </msup> <mi>R</mi> <mi>d</mi> <mi>R</mi> </mfenced> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </msup> <mo>,</mo> </mrow> </math></EquationSource> </Equation>where the bilinear Bochner-Riesz means is given by <Equation ID="Equ2"> <EquationSource Format="TEX">\(\begin{aligned} \mathcal {B}_R^\alpha (f, g)(x)=\int _{\mathbb {R}^n} \int _{\mathbb {R}^n}\left( 1-\frac{|\xi |^2+|\eta |^2}{R^2}\right) _{+}^\alpha \hat{f}(\xi ) \hat{g}(\eta ) e^{2 \pi i x \cdot (\xi +\eta )} d \xi d \eta , \quad R&gt;0. \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <msubsup> <mi mathvariant="script">B</mi> <mi>R</mi> <mi>α</mi> </msubsup> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo>,</mo> <mi>g</mi> <mo stretchy="false">)</mo> </mrow> <mrow> <mo stretchy="false">(</mo> <mi>x</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msub> <mo>∫</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> </msub> <msub> <mo>∫</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> </msub> <msubsup> <mfenced close=")" open="("> <mn>1</mn> <mo>-</mo> <mfrac> <mrow> <msup> <mrow> <mo stretchy="false">|</mo> <mi>ξ</mi> <mo stretchy="false">|</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo stretchy="false">|</mo> <mi>η</mi> <mo stretchy="false">|</mo> </mrow> <mn>2</mn> </msup> </mrow> <msup> <mi>R</mi> <mn>2</mn> </msup> </mfrac> </mfenced> <mrow> <mo>+</mo> </mrow> <mi>α</mi> </msubsup> <mover accent="true"> <mi>f</mi> <mo stretchy="false">^</mo> </mover> <mrow> <mo stretchy="false">(</mo> <mi>ξ</mi> <mo stretchy="false">)</mo> </mrow> <mover accent="true"> <mi>g</mi> <mo stretchy="false">^</mo> </mover> <mrow> <mo stretchy="false">(</mo> <mi>η</mi> <mo stretchy="false">)</mo> </mrow> <msup> <mi>e</mi> <mrow> <mn>2</mn> <mi>π</mi> <mi>i</mi> <mi>x</mi> <mo>·</mo> <mo stretchy="false">(</mo> <mi>ξ</mi> <mo>+</mo> <mi>η</mi> <mo stretchy="false">)</mo> </mrow> </msup> <mi>d</mi> <mi>ξ</mi> <mi>d</mi> <mi>η</mi> <mo>,</mo> <mspace width="1em" /> <mi>R</mi> <mo>&gt;</mo> <mn>0</mn> <mo>.</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>The weighted strong and weak type estimates for the operator <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\mathcal {G}^\alpha \)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mrow> <mi mathvariant="script">G</mi> </mrow> <mi>α</mi> </msup> </math></EquationSource> </InlineEquation> and its associated commutators are given. We also show that the commutators <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\([\vec {b},\mathcal {G}^\alpha ]\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">[</mo> <mover accent="true"> <mi>b</mi> <mo stretchy="false">→</mo> </mover> <mo>,</mo> <msup> <mrow> <mi mathvariant="script">G</mi> </mrow> <mi>α</mi> </msup> <mo stretchy="false">]</mo> </mrow> </math></EquationSource> </InlineEquation> are compact from <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(L^{p_1}(w_1)\times L^{p_2}(w_2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>L</mi> <msub> <mi>p</mi> <mn>1</mn> </msub> </msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi>w</mi> <mn>1</mn> </msub> <mo stretchy="false">)</mo> </mrow> <mo>×</mo> <msup> <mi>L</mi> <msub> <mi>p</mi> <mn>2</mn> </msub> </msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi>w</mi> <mn>2</mn> </msub> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> to <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(L^p(v_{\vec {w}})\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msup> <mi>L</mi> <mi>p</mi> </msup> <mrow> <mo stretchy="false">(</mo> <msub> <mi>v</mi> <mover accent="true"> <mi>w</mi> <mo stretchy="false">→</mo> </mover> </msub> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> for <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(1&lt;p_1,p_2&lt;\infty ,\frac{1}{p}=\frac{1}{p_1}+\frac{1}{p_2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mn>1</mn> <mo>&lt;</mo> <msub> <mi>p</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>p</mi> <mn>2</mn> </msub> <mo>&lt;</mo> <mi>∞</mi> <mo>,</mo> <mfrac> <mn>1</mn> <mi>p</mi> </mfrac> <mo>=</mo> <mfrac> <mn>1</mn> <msub> <mi>p</mi> <mn>1</mn> </msub> </mfrac> <mo>+</mo> <mfrac> <mn>1</mn> <msub> <mi>p</mi> <mn>2</mn> </msub> </mfrac> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\alpha &gt;n-\frac{1}{2}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>α</mi> <mo>&gt;</mo> <mi>n</mi> <mo>-</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> </mrow> </math></EquationSource> </InlineEquation>, where <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\vec {b}=(b_1,b_2)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mover accent="true"> <mi>b</mi> <mo stretchy="false">→</mo> </mover> <mo>=</mo> <mrow> <mo stretchy="false">(</mo> <msub> <mi>b</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>b</mi> <mn>2</mn> </msub> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(b_1,b_2\in {\text{ CMO }}(\mathbb {R}^n)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>b</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>b</mi> <mn>2</mn> </msub> <mo>∈</mo> <mrow> <mspace width="0.333333em" /> <mtext>CMO</mtext> <mspace width="0.333333em" /> </mrow> <mrow> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\(\vec {w}=\left( w_1, w_2\right) \in {A}_{\vec {p}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mover accent="true"> <mi>w</mi> <mo stretchy="false">→</mo> </mover> <mo>=</mo> <mfenced close=")" open="("> <msub> <mi>w</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>w</mi> <mn>2</mn> </msub> </mfenced> <mo>∈</mo> <msub> <mi>A</mi> <mover accent="true"> <mi>p</mi> <mo stretchy="false">→</mo> </mover> </msub> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(v_{\vec {w}}=w_1^{{p}/{p_1}} w_2^{{p}/{ p_2}}.\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>v</mi> <mover accent="true"> <mi>w</mi> <mo stretchy="false">→</mo> </mover> </msub> <mo>=</mo> <msubsup> <mi>w</mi> <mn>1</mn> <mrow> <mi>p</mi> <mo stretchy="false">/</mo> <msub> <mi>p</mi> <mn>1</mn> </msub> </mrow> </msubsup> <msubsup> <mi>w</mi> <mn>2</mn> <mrow> <mi>p</mi> <mo stretchy="false">/</mo> <msub> <mi>p</mi> <mn>2</mn> </msub> </mrow> </msubsup> <mo>.</mo> </mrow> </math></EquationSource> </InlineEquation> Here <InlineEquation ID="IEq11"> <EquationSource Format="TEX">\(\textrm{CMO}(\mathbb {R}^n)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>CMO</mtext> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is the closure of <InlineEquation ID="IEq12"> <EquationSource Format="TEX">\({C}_c^\infty (\mathbb {R}^n)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msubsup> <mi>C</mi> <mi>c</mi> <mi>∞</mi> </msubsup> <mrow> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> in the <InlineEquation ID="IEq13"> <EquationSource Format="TEX">\(\textrm{BMO}(\mathbb {R}^n)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mtext>BMO</mtext> <mo stretchy="false">(</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mi>n</mi> </msup> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> topology.</p>

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On the Commutators of Bilinear Stein’s Square Functions Associated with Bochner-Riesz Means

  • Chunmei Zhang,
  • Xiaoting Qiu,
  • Qingying Xue

摘要

In this paper, we investigate the bilinear Stein’s square functions associated with the bilinear Bochner-Riesz means, defined as \( \mathcal {G}^\alpha (f, g)(x):=\left( \int _0^{\infty }\left| \frac{\partial }{\partial R} \mathcal {B}_R^{\alpha +1}(f, g)(x)\right| ^2 R d R\right) ^{\frac{1}{2}}, \) G α ( f , g ) ( x ) : = 0 R B R α + 1 ( f , g ) ( x ) 2 R d R 1 2 , where the bilinear Bochner-Riesz means is given by \(\begin{aligned} \mathcal {B}_R^\alpha (f, g)(x)=\int _{\mathbb {R}^n} \int _{\mathbb {R}^n}\left( 1-\frac{|\xi |^2+|\eta |^2}{R^2}\right) _{+}^\alpha \hat{f}(\xi ) \hat{g}(\eta ) e^{2 \pi i x \cdot (\xi +\eta )} d \xi d \eta , \quad R>0. \end{aligned}\) B R α ( f , g ) ( x ) = R n R n 1 - | ξ | 2 + | η | 2 R 2 + α f ^ ( ξ ) g ^ ( η ) e 2 π i x · ( ξ + η ) d ξ d η , R > 0 . The weighted strong and weak type estimates for the operator \(\mathcal {G}^\alpha \) G α and its associated commutators are given. We also show that the commutators \([\vec {b},\mathcal {G}^\alpha ]\) [ b , G α ] are compact from \(L^{p_1}(w_1)\times L^{p_2}(w_2)\) L p 1 ( w 1 ) × L p 2 ( w 2 ) to \(L^p(v_{\vec {w}})\) L p ( v w ) for \(1<p_1,p_2<\infty ,\frac{1}{p}=\frac{1}{p_1}+\frac{1}{p_2}\) 1 < p 1 , p 2 < , 1 p = 1 p 1 + 1 p 2 and \(\alpha >n-\frac{1}{2}\) α > n - 1 2 , where \(\vec {b}=(b_1,b_2)\) b = ( b 1 , b 2 ) , \(b_1,b_2\in {\text{ CMO }}(\mathbb {R}^n)\) b 1 , b 2 CMO ( R n ) , \(\vec {w}=\left( w_1, w_2\right) \in {A}_{\vec {p}}\) w = w 1 , w 2 A p and \(v_{\vec {w}}=w_1^{{p}/{p_1}} w_2^{{p}/{ p_2}}.\) v w = w 1 p / p 1 w 2 p / p 2 . Here \(\textrm{CMO}(\mathbb {R}^n)\) CMO ( R n ) is the closure of \({C}_c^\infty (\mathbb {R}^n)\) C c ( R n ) in the \(\textrm{BMO}(\mathbb {R}^n)\) BMO ( R n ) topology.