<p>A functional Hilbert space is defined as the Hilbert space <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi mathvariant="script">K</mi> </math></EquationSource> <EquationSource Format="TEX">$\mathcal{K}$</EquationSource> </InlineEquation> of complex-valued functions defined on a set Θ. In this space, the evaluation functionals <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="93" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>ψ</mi> <mi>ε</mi> </msub> <mo stretchy="false">(</mo> <mi>h</mi> <mo stretchy="false">)</mo> <mo>=</mo> <mi>h</mi> <mo stretchy="false">(</mo> <mi>ε</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$\psi _{\varepsilon}(h) = h(\varepsilon )$</EquationSource> </InlineEquation>, for <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq3.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="43" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>ε</mi> <mo>∈</mo> <mi mathvariant="normal">Θ</mi> </math></EquationSource> <EquationSource Format="TEX">$\varepsilon \in \Theta $</EquationSource> </InlineEquation>, are continuous on <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq1.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="18" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi mathvariant="script">K</mi> </math></EquationSource> <EquationSource Format="TEX">$\mathcal{K}$</EquationSource> </InlineEquation>. In this paper, we introduce the mean-Berezin norm <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq5.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="44" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mrow> <mo stretchy="false">∥</mo> <mo>⋅</mo> <mo stretchy="false">∥</mo> </mrow> <msub> <mi>ρ</mi> <mi>t</mi> </msub> </msub> </math></EquationSource> <EquationSource Format="TEX">$\| \cdot \|_{\rho _{t}}$</EquationSource> </InlineEquation>, defined as follows: <Equation ID="Equa"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_Equa.gif" Format="GIF" Height="39" Rendition="HTML" Resolution="72" Type="Linedraw" Width="480" /> </MediaObject> <EquationSource Format="MATHML"><math> <msub> <mrow> <mo stretchy="false">∥</mo> <mi>G</mi> <mo stretchy="false">∥</mo> </mrow> <msub> <mi>M</mi> <msub> <mi>ρ</mi> <mi>t</mi> </msub> </msub> </msub> <mo>=</mo> <munder> <mo movablelimits="false">sup</mo> <mrow> <mi>κ</mi> <mo>,</mo> <mi>ξ</mi> <mo>∈</mo> <mi mathvariant="normal">Θ</mi> </mrow> </munder> <mrow> <mo>{</mo> <mrow> <mo>(</mo> <mo maxsize="2.4ex" minsize="2.4ex" stretchy="true">|</mo> <mo stretchy="false">〈</mo> <mi>G</mi> <msub> <mover accent="true"> <mi>k</mi> <mo stretchy="false">ˆ</mo> </mover> <mi>κ</mi> </msub> <mo>,</mo> <msub> <mover accent="true"> <mi>k</mi> <mo stretchy="false">ˆ</mo> </mover> <mi>ξ</mi> </msub> <mo stretchy="false">〉</mo> <mo maxsize="2.4ex" minsize="2.4ex" stretchy="true">|</mo> <mo>)</mo> </mrow> <msub> <mi>ρ</mi> <mi>t</mi> </msub> <mrow> <mo>(</mo> <mo maxsize="2.4ex" minsize="2.4ex" stretchy="true">|</mo> <mo stretchy="false">〈</mo> <msup> <mi>G</mi> <mo>∗</mo> </msup> <msub> <mover accent="true"> <mi>k</mi> <mo stretchy="false">ˆ</mo> </mover> <mi>κ</mi> </msub> <mo>,</mo> <msub> <mover accent="true"> <mi>k</mi> <mo stretchy="false">ˆ</mo> </mover> <mi>ξ</mi> </msub> <mo stretchy="false">〉</mo> <mo maxsize="2.4ex" minsize="2.4ex" stretchy="true">|</mo> <mo>)</mo> </mrow> <mo>}</mo> </mrow> <mo>,</mo> <mspace width="1em" /> <mtext>for&#xa0;</mtext> <mn>0</mn> <mo>⩽</mo> <mi>t</mi> <mo>⩽</mo> <mn>1</mn> <mo>,</mo> </math></EquationSource> <EquationSource Format="TEX">\( \| G \|_{M_{\rho _{t}}} = \sup _{\kappa , \xi \in \Theta} \left \{ \left (\big| \langle G \hat{k}_{\kappa}, \hat{k}_{\xi} \rangle \big| \right ) \rho _{t} \left ( \big| \langle G^{*} \hat{k}_{\kappa}, \hat{k}_{\xi} \rangle \big| \right ) \right \}, \quad \text{for } 0 \leqslant t \leqslant 1, \)</EquationSource> </Equation> where <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="76" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>G</mi> <mo>∈</mo> <mi mathvariant="script">O</mi> <mo stretchy="false">(</mo> <mi mathvariant="script">K</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$G \in \mathcal{O}(\mathcal{K})$</EquationSource> </InlineEquation> and <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq7.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="17" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msub> <mi>ρ</mi> <mi>t</mi> </msub> </math></EquationSource> <EquationSource Format="TEX">$\rho _{t}$</EquationSource> </InlineEquation> represents an interpolation path of a symmetric mean <i>ρ</i>. Using the definition of the mean-Berezin norm, we explore some related new inequalities For instance, if <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq8.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="76" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>G</mi> <mo>∈</mo> <mi mathvariant="script">O</mi> <mo stretchy="false">(</mo> <mi mathvariant="script">K</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$G\in \mathcal{O}(\mathcal{K})$</EquationSource> </InlineEquation>, then <Equation ID="Equb"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_Equb.gif" Format="GIF" Height="36" Rendition="HTML" Resolution="72" Type="Linedraw" Width="264" /> </MediaObject> <EquationSource Format="MATHML"><math> <mfrac> <mrow> <mn>1</mn> </mrow> <mn>2</mn> </mfrac> <msqrt> <msub> <mrow> <mo>∥</mo> <mo stretchy="false">|</mo> <mi>G</mi> <msup> <mo stretchy="false">|</mo> <mrow> <mn>2</mn> <mi>r</mi> </mrow> </msup> <mo>+</mo> <mo stretchy="false">|</mo> <msup> <mi>G</mi> <mo>∗</mo> </msup> <msup> <mo stretchy="false">|</mo> <mrow> <mn>2</mn> <mo stretchy="false">(</mo> <mn>1</mn> <mo>−</mo> <mi>r</mi> <mo stretchy="false">)</mo> </mrow> </msup> <mo>∥</mo> </mrow> <mtext mathvariant="bold">ber</mtext> </msub> </msqrt> <mo>⩾</mo> <msub> <mrow> <mo stretchy="false">∥</mo> <mi>G</mi> <mo stretchy="false">∥</mo> </mrow> <msub> <mi>M</mi> <mi>ρ</mi> </msub> </msub> <mo>,</mo> </math></EquationSource> <EquationSource Format="TEX">\( \frac{1}{2}\sqrt{\left \Vert \vert G\vert ^{2r}+\vert G^{*}\vert ^{2(1-r)} \right \Vert _{\textbf{ber}}}\geqslant \Vert G\Vert _{M_{\rho}}, \)</EquationSource> </Equation> where <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq9.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="71" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mn>0</mn> <mo>⩽</mo> <mi>r</mi> <mo>⩽</mo> <mn>1</mn> </math></EquationSource> <EquationSource Format="TEX">$0\leqslant r\leqslant 1$</EquationSource> </InlineEquation> and <i>ρ</i> is a mean such that <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3385_Article_IEq10.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>ρ</mi> <mo>⩽</mo> <mi mathvariant="normal">∇</mi> </math></EquationSource> <EquationSource Format="TEX">$\rho \leqslant \nabla $</EquationSource> </InlineEquation>.</p>

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A new mean-Berezin norm for operators in reproducing kernel Hilbert spaces

  • Mojtaba Bakherad

摘要

A functional Hilbert space is defined as the Hilbert space K $\mathcal{K}$ of complex-valued functions defined on a set Θ. In this space, the evaluation functionals ψ ε ( h ) = h ( ε ) $\psi _{\varepsilon}(h) = h(\varepsilon )$ , for ε Θ $\varepsilon \in \Theta $ , are continuous on K $\mathcal{K}$ . In this paper, we introduce the mean-Berezin norm ρ t $\| \cdot \|_{\rho _{t}}$ , defined as follows: G M ρ t = sup κ , ξ Θ { ( | G k ˆ κ , k ˆ ξ | ) ρ t ( | G k ˆ κ , k ˆ ξ | ) } , for  0 t 1 , \( \| G \|_{M_{\rho _{t}}} = \sup _{\kappa , \xi \in \Theta} \left \{ \left (\big| \langle G \hat{k}_{\kappa}, \hat{k}_{\xi} \rangle \big| \right ) \rho _{t} \left ( \big| \langle G^{*} \hat{k}_{\kappa}, \hat{k}_{\xi} \rangle \big| \right ) \right \}, \quad \text{for } 0 \leqslant t \leqslant 1, \) where G O ( K ) $G \in \mathcal{O}(\mathcal{K})$ and ρ t $\rho _{t}$ represents an interpolation path of a symmetric mean ρ. Using the definition of the mean-Berezin norm, we explore some related new inequalities For instance, if G O ( K ) $G\in \mathcal{O}(\mathcal{K})$ , then 1 2 | G | 2 r + | G | 2 ( 1 r ) ber G M ρ , \( \frac{1}{2}\sqrt{\left \Vert \vert G\vert ^{2r}+\vert G^{*}\vert ^{2(1-r)} \right \Vert _{\textbf{ber}}}\geqslant \Vert G\Vert _{M_{\rho}}, \) where 0 r 1 $0\leqslant r\leqslant 1$ and ρ is a mean such that ρ $\rho \leqslant \nabla $ .