<p>It is shown, among other inequalities, that if <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(A, B, X_1, X_2\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>A</mi> <mo>,</mo> <mi>B</mi> <mo>,</mo> <msub> <mi>X</mi> <mn>1</mn> </msub> <mo>,</mo> <msub> <mi>X</mi> <mn>2</mn> </msub> </mrow> </math></EquationSource> </InlineEquation> are <i>n</i> by <i>n</i> complex matrices where <i>A</i>,&#xa0;<i>B</i> are positive semidefinite matrices, if <i>g</i> is a nonnegative increasing concave function on <InlineEquation ID="IEq2"> <EquationSource Format="TEX">\([0, \infty )\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">[</mo> <mn>0</mn> <mo>,</mo> <mi>∞</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(p,q\in (0,1)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>p</mi> <mo>,</mo> <mi>q</mi> <mo>∈</mo> <mo stretchy="false">(</mo> <mn>0</mn> <mo>,</mo> <mn>1</mn> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, then <Equation ID="Equ16"> <EquationSource Format="TEX">\(\begin{aligned} |||g(|(X_2AX_1 + X_1BX_2) \oplus 0|)||| \le |||N \oplus K||| \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> <mi>g</mi> <mo stretchy="false">(</mo> <mo stretchy="false">|</mo> <mrow> <mo stretchy="false">(</mo> <msub> <mi>X</mi> <mn>2</mn> </msub> <mi>A</mi> <msub> <mi>X</mi> <mn>1</mn> </msub> <mo>+</mo> <msub> <mi>X</mi> <mn>1</mn> </msub> <mi>B</mi> <msub> <mi>X</mi> <mn>2</mn> </msub> <mo stretchy="false">)</mo> </mrow> <mo>⊕</mo> <mn>0</mn> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> <mo>≤</mo> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> <mi>N</mi> <mo>⊕</mo> <mi>K</mi> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> <mo stretchy="false">|</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation>for every unitarily invariant norm, where <Equation ID="Equ17"> <EquationSource Format="TEX">\(N=g(N_{1})+g(|Z^*|),~~K=g(N_2)+g(|Z|),\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi>N</mi> <mo>=</mo> <mi>g</mi> <mrow> <mo stretchy="false">(</mo> <msub> <mi>N</mi> <mn>1</mn> </msub> <mo stretchy="false">)</mo> </mrow> <mo>+</mo> <mrow> <mi>g</mi> <mo stretchy="false">(</mo> <mo stretchy="false">|</mo> </mrow> <msup> <mi>Z</mi> <mo>∗</mo> </msup> <mrow> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> <mo>,</mo> <mspace width="3.33333pt" /> <mspace width="3.33333pt" /> <mi>K</mi> </mrow> <mo>=</mo> <mi>g</mi> <mrow> <mo stretchy="false">(</mo> <msub> <mi>N</mi> <mn>2</mn> </msub> <mo stretchy="false">)</mo> </mrow> <mo>+</mo> <mi>g</mi> <mrow> <mo stretchy="false">(</mo> <mo stretchy="false">|</mo> <mi>Z</mi> <mo stretchy="false">|</mo> <mo stretchy="false">)</mo> </mrow> <mo>,</mo> </mrow> </math></EquationSource> </Equation><Equation ID="Equ18"> <EquationSource Format="TEX">\(N_{1}=\frac{1}{2}(A^{p}|X_2|^{2}A^{p}+A^{1-p}|X_1^{*}|^{2}A^{1-p}),\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msub> <mi>N</mi> <mn>1</mn> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo stretchy="false">(</mo> </mrow> <msup> <mi>A</mi> <mi>p</mi> </msup> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>X</mi> <mn>2</mn> </msub> <msup> <mrow> <mo stretchy="false">|</mo> </mrow> <mn>2</mn> </msup> <msup> <mi>A</mi> <mi>p</mi> </msup> <mo>+</mo> <msup> <mi>A</mi> <mrow> <mn>1</mn> <mo>-</mo> <mi>p</mi> </mrow> </msup> <mrow> <mo stretchy="false">|</mo> </mrow> <msubsup> <mi>X</mi> <mn>1</mn> <mrow> <mrow /> <mo>∗</mo> </mrow> </msubsup> <mrow> <msup> <mo stretchy="false">|</mo> <mn>2</mn> </msup> <msup> <mi>A</mi> <mrow> <mn>1</mn> <mo>-</mo> <mi>p</mi> </mrow> </msup> <mo stretchy="false">)</mo> </mrow> <mo>,</mo> </mrow> </math></EquationSource> </Equation><Equation ID="Equ19"> <EquationSource Format="TEX">\( N_2=\frac{1}{2}(B^{1-q}|X_1|^{2}B^{1-q}+B^{q}|X_2^{*}|^{2}B^{q}) \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <msub> <mi>N</mi> <mn>2</mn> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo stretchy="false">(</mo> </mrow> <msup> <mi>B</mi> <mrow> <mn>1</mn> <mo>-</mo> <mi>q</mi> </mrow> </msup> <mrow> <mo stretchy="false">|</mo> </mrow> <msub> <mi>X</mi> <mn>1</mn> </msub> <msup> <mrow> <mo stretchy="false">|</mo> </mrow> <mn>2</mn> </msup> <msup> <mi>B</mi> <mrow> <mn>1</mn> <mo>-</mo> <mi>q</mi> </mrow> </msup> <mo>+</mo> <msup> <mi>B</mi> <mi>q</mi> </msup> <mrow> <mo stretchy="false">|</mo> </mrow> <msubsup> <mi>X</mi> <mn>2</mn> <mrow> <mrow /> <mo>∗</mo> </mrow> </msubsup> <mrow> <msup> <mo stretchy="false">|</mo> <mn>2</mn> </msup> <msup> <mi>B</mi> <mi>q</mi> </msup> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </Equation>and <Equation ID="Equ20"> <EquationSource Format="TEX">\( Z=\frac{1}{2}(A^{p}X_2^{*}X_1B^{1-q}+A^{1-p}X_1X_2^{*}B^{q}). \)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mi>Z</mi> <mo>=</mo> <mfrac> <mn>1</mn> <mn>2</mn> </mfrac> <mrow> <mo stretchy="false">(</mo> <msup> <mi>A</mi> <mi>p</mi> </msup> <msubsup> <mi>X</mi> <mn>2</mn> <mrow> <mrow /> <mo>∗</mo> </mrow> </msubsup> <msub> <mi>X</mi> <mn>1</mn> </msub> <msup> <mi>B</mi> <mrow> <mn>1</mn> <mo>-</mo> <mi>q</mi> </mrow> </msup> <mo>+</mo> <msup> <mi>A</mi> <mrow> <mn>1</mn> <mo>-</mo> <mi>p</mi> </mrow> </msup> <msub> <mi>X</mi> <mn>1</mn> </msub> <msubsup> <mi>X</mi> <mn>2</mn> <mrow> <mrow /> <mo>∗</mo> </mrow> </msubsup> <msup> <mi>B</mi> <mi>q</mi> </msup> <mo stretchy="false">)</mo> </mrow> <mo>.</mo> </mrow> </math></EquationSource> </Equation>Several related singular value inequalities and norm inequalities are also given.</p>

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Further singular value inequalities and applications

  • Manal Al-Labadi,
  • Wasim Audeh

摘要

It is shown, among other inequalities, that if \(A, B, X_1, X_2\) A , B , X 1 , X 2 are n by n complex matrices where AB are positive semidefinite matrices, if g is a nonnegative increasing concave function on \([0, \infty )\) [ 0 , ) and \(p,q\in (0,1)\) p , q ( 0 , 1 ) , then \(\begin{aligned} |||g(|(X_2AX_1 + X_1BX_2) \oplus 0|)||| \le |||N \oplus K||| \end{aligned}\) | | | g ( | ( X 2 A X 1 + X 1 B X 2 ) 0 | ) | | | | | | N K | | | for every unitarily invariant norm, where \(N=g(N_{1})+g(|Z^*|),~~K=g(N_2)+g(|Z|),\) N = g ( N 1 ) + g ( | Z | ) , K = g ( N 2 ) + g ( | Z | ) , \(N_{1}=\frac{1}{2}(A^{p}|X_2|^{2}A^{p}+A^{1-p}|X_1^{*}|^{2}A^{1-p}),\) N 1 = 1 2 ( A p | X 2 | 2 A p + A 1 - p | X 1 | 2 A 1 - p ) , \( N_2=\frac{1}{2}(B^{1-q}|X_1|^{2}B^{1-q}+B^{q}|X_2^{*}|^{2}B^{q}) \) N 2 = 1 2 ( B 1 - q | X 1 | 2 B 1 - q + B q | X 2 | 2 B q ) and \( Z=\frac{1}{2}(A^{p}X_2^{*}X_1B^{1-q}+A^{1-p}X_1X_2^{*}B^{q}). \) Z = 1 2 ( A p X 2 X 1 B 1 - q + A 1 - p X 1 X 2 B q ) . Several related singular value inequalities and norm inequalities are also given.