<p>This paper investigates power vector inequalities for bounded linear operator pairs <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mo stretchy="false">(</mo> <mi>B</mi> <mo>,</mo> <mi>C</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$(B,C)$</EquationSource> </InlineEquation> in a Hilbert space <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi mathvariant="script">H</mi> </math></EquationSource> <EquationSource Format="TEX">$\mathcal{H}$</EquationSource> </InlineEquation>. By leveraging vector inequalities derived by the second author for inner products and norms, we establish various power vector inequalities for operator pairs in Hilbert spaces. Specifically, we analyze cases where <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mo stretchy="false">(</mo> <mi>B</mi> <mo>,</mo> <mi>C</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$(B,C)$</EquationSource> </InlineEquation> corresponds to <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="53" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mrow> <mo>(</mo> <mi>A</mi> <mo>,</mo> <msup> <mi>A</mi> <mo>∗</mo> </msup> <mo>)</mo> </mrow> </math></EquationSource> <EquationSource Format="TEX">$\left (A,A^{\ast }\right )$</EquationSource> </InlineEquation> or <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="95" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mrow> <mo>(</mo> <mi mathvariant="fraktur">R</mi> <mo stretchy="false">(</mo> <mi>A</mi> <mo stretchy="false">)</mo> <mo>,</mo> <mi mathvariant="fraktur">I</mi> <mo stretchy="false">(</mo> <mi>A</mi> <mo stretchy="false">)</mo> <mo>)</mo> </mrow> </math></EquationSource> <EquationSource Format="TEX">$\left (\mathfrak{R}(A),\mathfrak{I}(A)\right )$</EquationSource> </InlineEquation>, where <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq6.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="22" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <msup> <mi>A</mi> <mo>∗</mo> </msup> </math></EquationSource> <EquationSource Format="TEX">$A^{\ast}$</EquationSource> </InlineEquation>, <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="41" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi mathvariant="fraktur">R</mi> <mo stretchy="false">(</mo> <mi>A</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$\mathfrak{R}(A)$</EquationSource> </InlineEquation>, and <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq8.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="36" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi mathvariant="fraktur">I</mi> <mo stretchy="false">(</mo> <mi>A</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$\mathfrak{I}(A)$</EquationSource> </InlineEquation> denote the adjoint, real, and imaginary parts of <i>A</i>. This analysis leads to the derivation of vector, norm, and numerical radius inequalities for single operators. Additionally, we derive power inequalities for the <i>s</i>-<i>r</i>-norm and <i>s</i>-<i>r</i>-numerical radius (<InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq9.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="41" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi>r</mi> <mo>≥</mo> <mn>1</mn> </math></EquationSource> <EquationSource Format="TEX">$r\geq 1$</EquationSource> </InlineEquation>) of the operator pair <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mo stretchy="false">(</mo> <mi>B</mi> <mo>,</mo> <mi>C</mi> <mo stretchy="false">)</mo> </math></EquationSource> <EquationSource Format="TEX">$(B,C)$</EquationSource> </InlineEquation>, which generalize the Euclidean norm and Euclidean numerical radius for operator pairs. Finally, we apply these results to derive corresponding inequalities for a single bounded linear operator <i>A</i> on <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13660_2025_3338_Article_IEq2.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="MATHML"><math> <mi mathvariant="script">H</mi> </math></EquationSource> <EquationSource Format="TEX">$\mathcal{H}$</EquationSource> </InlineEquation>.</p>

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More power vector bounds for operator pairs in Hilbert spaces with applications

  • Najla Altwaijry,
  • Silvestru Sever Dragomir,
  • Kais Feki

摘要

This paper investigates power vector inequalities for bounded linear operator pairs ( B , C ) $(B,C)$ in a Hilbert space H $\mathcal{H}$ . By leveraging vector inequalities derived by the second author for inner products and norms, we establish various power vector inequalities for operator pairs in Hilbert spaces. Specifically, we analyze cases where ( B , C ) $(B,C)$ corresponds to ( A , A ) $\left (A,A^{\ast }\right )$ or ( R ( A ) , I ( A ) ) $\left (\mathfrak{R}(A),\mathfrak{I}(A)\right )$ , where A $A^{\ast}$ , R ( A ) $\mathfrak{R}(A)$ , and I ( A ) $\mathfrak{I}(A)$ denote the adjoint, real, and imaginary parts of A. This analysis leads to the derivation of vector, norm, and numerical radius inequalities for single operators. Additionally, we derive power inequalities for the s-r-norm and s-r-numerical radius ( r 1 $r\geq 1$ ) of the operator pair ( B , C ) $(B,C)$ , which generalize the Euclidean norm and Euclidean numerical radius for operator pairs. Finally, we apply these results to derive corresponding inequalities for a single bounded linear operator A on H $\mathcal{H}$ .