<p>Time-frequency localization operators, originally introduced by Daubechies (1988), provide a framework for localizing signals in the phase space and have become a central tool in time-frequency analysis. In this paper we introduce and study a broad generalization of these operators, called <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\({\mathcal {A}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">A</mi> </math></EquationSource> </InlineEquation>-<i>localization operators</i>, associated with a metaplectic Wigner distribution <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(W_{\mathcal {A}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>W</mi> <mi mathvariant="script">A</mi> </msub> </math></EquationSource> </InlineEquation> and the corresponding <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\({\mathcal {A}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">A</mi> </math></EquationSource> </InlineEquation>-pseudodifferential calculus. We first show that the classical relation between localization operators and Weyl quantization extends to any <i>covariant metaplectic Wigner distribution</i>. Specifically, if <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(W_{\mathcal {A}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>W</mi> <mi mathvariant="script">A</mi> </msub> </math></EquationSource> </InlineEquation> satisfies the covariance property <Equation ID="Equ53"> <EquationSource Format="TEX">\( W_{\mathcal {A}}(\pi (z)f,\pi (z)g)=T_zW_{\mathcal {A}}(f,g), \qquad z\in \mathbb {R}^{2d}, \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msub> <mi>W</mi> <mi mathvariant="script">A</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>π</mi> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mi>f</mi> <mo>,</mo> <mi>π</mi> <mrow> <mo stretchy="false">(</mo> <mi>z</mi> <mo stretchy="false">)</mo> </mrow> <mi>g</mi> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <msub> <mi>T</mi> <mi>z</mi> </msub> <msub> <mi>W</mi> <mi mathvariant="script">A</mi> </msub> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo>,</mo> <mi>g</mi> <mo stretchy="false">)</mo> </mrow> <mo>,</mo> <mspace width="2em" /> <mi>z</mi> <mo>∈</mo> <msup> <mrow> <mi mathvariant="double-struck">R</mi> </mrow> <mrow> <mn>2</mn> <mi>d</mi> </mrow> </msup> <mo>,</mo> </mrow> </math></EquationSource> </Equation>then <Equation ID="Equ54"> <EquationSource Format="TEX">\( A_{a}^{\varphi _1,\varphi _2} = \operatorname {Op}_{\mathcal {A}}\big (a * W_{\mathcal {A}}(\varphi _2,\varphi _1)\big ), \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msubsup> <mi>A</mi> <mrow> <mi>a</mi> </mrow> <mrow> <msub> <mi>φ</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>φ</mi> <mn>2</mn> </msub> </mrow> </msubsup> <mo>=</mo> <msub> <mo>Op</mo> <mi mathvariant="script">A</mi> </msub> <mrow> <mo maxsize="1.2em" minsize="1.2em" stretchy="true">(</mo> </mrow> <mi>a</mi> <mrow /> <mo>∗</mo> <msub> <mi>W</mi> <mi mathvariant="script">A</mi> </msub> <mrow> <mo stretchy="false">(</mo> <msub> <mi>φ</mi> <mn>2</mn> </msub> <mo>,</mo> <msub> <mi>φ</mi> <mn>1</mn> </msub> <mo stretchy="false">)</mo> </mrow> <mrow> <mo maxsize="1.2em" minsize="1.2em" stretchy="true">)</mo> </mrow> <mo>,</mo> </mrow> </math></EquationSource> </Equation>and conversely, this identity characterizes covariance. This result extends the recent representation formula of Bastianoni and Teofanov for <InlineEquation ID="IEq8"> <EquationSource Format="TEX">\(\tau \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>τ</mi> </math></EquationSource> </InlineEquation>-operators to the full metaplectic framework. We then define the <InlineEquation ID="IEq9"> <EquationSource Format="TEX">\({\mathcal {A}}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="script">A</mi> </math></EquationSource> </InlineEquation>-localization operator <InlineEquation ID="IEq10"> <EquationSource Format="TEX">\(A_{a,{\mathcal {A}}}^{\varphi _1,\varphi _2}\)</EquationSource> <EquationSource Format="MATHML"><math> <msubsup> <mi>A</mi> <mrow> <mi>a</mi> <mo>,</mo> <mi mathvariant="script">A</mi> </mrow> <mrow> <msub> <mi>φ</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>φ</mi> <mn>2</mn> </msub> </mrow> </msubsup> </math></EquationSource> </InlineEquation> and investigate its analytical properties. We establish boundedness results on modulation spaces and provide sufficient conditions for Schatten-von Neumann class membership. These findings connect the structure of metaplectic representations with time-frequency localization theory, offering a unified approach to quantization and signal analysis.</p>

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\({\mathcal {A}}\)-localization operators

  • Elena Cordero,
  • Edoardo Pucci

摘要

Time-frequency localization operators, originally introduced by Daubechies (1988), provide a framework for localizing signals in the phase space and have become a central tool in time-frequency analysis. In this paper we introduce and study a broad generalization of these operators, called \({\mathcal {A}}\) A -localization operators, associated with a metaplectic Wigner distribution \(W_{\mathcal {A}}\) W A and the corresponding \({\mathcal {A}}\) A -pseudodifferential calculus. We first show that the classical relation between localization operators and Weyl quantization extends to any covariant metaplectic Wigner distribution. Specifically, if \(W_{\mathcal {A}}\) W A satisfies the covariance property \( W_{\mathcal {A}}(\pi (z)f,\pi (z)g)=T_zW_{\mathcal {A}}(f,g), \qquad z\in \mathbb {R}^{2d}, \) W A ( π ( z ) f , π ( z ) g ) = T z W A ( f , g ) , z R 2 d , then \( A_{a}^{\varphi _1,\varphi _2} = \operatorname {Op}_{\mathcal {A}}\big (a * W_{\mathcal {A}}(\varphi _2,\varphi _1)\big ), \) A a φ 1 , φ 2 = Op A ( a W A ( φ 2 , φ 1 ) ) , and conversely, this identity characterizes covariance. This result extends the recent representation formula of Bastianoni and Teofanov for \(\tau \) τ -operators to the full metaplectic framework. We then define the \({\mathcal {A}}\) A -localization operator \(A_{a,{\mathcal {A}}}^{\varphi _1,\varphi _2}\) A a , A φ 1 , φ 2 and investigate its analytical properties. We establish boundedness results on modulation spaces and provide sufficient conditions for Schatten-von Neumann class membership. These findings connect the structure of metaplectic representations with time-frequency localization theory, offering a unified approach to quantization and signal analysis.