<p>We find new limits of the Lie product formula type in Banach algebras with unit. Some sample results: Let <i>X</i>, <i>Y</i>, <i>Z</i> be Banach algebras with unit, <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_IEq1.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="150" /> </InlineMediaObject> <EquationSource Format="TEX">\( \left( x_{n},y_{n}\right) _{n\in \mathbb {N}}\subset X\times Y\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mfenced close=")" open="("> <msub> <mi>x</mi> <mi>n</mi> </msub> <mo>,</mo> <msub> <mi>y</mi> <mi>n</mi> </msub> </mfenced> <mrow> <mi>n</mi> <mo>∈</mo> <mi mathvariant="double-struck">N</mi> </mrow> </msub> <mo>⊂</mo> <mi>X</mi> <mo>×</mo> <mi>Y</mi> </mrow> </math></EquationSource> </InlineEquation> convergent sequences with <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_IEq2.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="108" /> </InlineMediaObject> <EquationSource Format="TEX">\(\lim \nolimits _{n\rightarrow \infty }x_{n}=x\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mo movablelimits="true">lim</mo> <mrow> <mi>n</mi> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </msub> <msub> <mi>x</mi> <mi>n</mi> </msub> <mo>=</mo> <mi>x</mi> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_IEq3.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="106" /> </InlineMediaObject> <EquationSource Format="TEX">\( \lim \nolimits _{n\rightarrow \infty }y_{n}=y\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mo movablelimits="true">lim</mo> <mrow> <mi>n</mi> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </msub> <msub> <mi>y</mi> <mi>n</mi> </msub> <mo>=</mo> <mi>y</mi> </mrow> </math></EquationSource> </InlineEquation> and <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_IEq4.gif" Format="GIF" Height="15" Rendition="HTML" Resolution="72" Type="Linedraw" Width="119" /> </InlineMediaObject> <EquationSource Format="TEX">\(T:X\times Y\rightarrow Z\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>T</mi> <mo>:</mo> <mi>X</mi> <mo>×</mo> <mi>Y</mi> <mo stretchy="false">→</mo> <mi>Z</mi> </mrow> </math></EquationSource> </InlineEquation> a continuous bilinear operator with <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_IEq5.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="86" /> </InlineMediaObject> <EquationSource Format="TEX">\(T\left( \textbf{1},\textbf{1}\right) = \textbf{1}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>T</mi> <mfenced close=")" open="("> <mn mathvariant="bold">1</mn> <mo>,</mo> <mn mathvariant="bold">1</mn> </mfenced> <mo>=</mo> <mn mathvariant="bold">1</mn> </mrow> </math></EquationSource> </InlineEquation>. Then for all sequences of natural numbers <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_IEq6.gif" Format="GIF" Height="20" Rendition="HTML" Resolution="72" Type="Linedraw" Width="54" /> </InlineMediaObject> <EquationSource Format="TEX">\(\left( a_{n}\right) _{n\in \mathbb {N}}\)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mfenced close=")" open="("> <msub> <mi>a</mi> <mi>n</mi> </msub> </mfenced> <mrow> <mi>n</mi> <mo>∈</mo> <mi mathvariant="double-struck">N</mi> </mrow> </msub> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_IEq7.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="115" /> </InlineMediaObject> <EquationSource Format="TEX">\(\lim \nolimits _{n\rightarrow \infty }a_{n}=\infty \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mo movablelimits="true">lim</mo> <mrow> <mi>n</mi> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </msub> <msub> <mi>a</mi> <mi>n</mi> </msub> <mo>=</mo> <mi>∞</mi> </mrow> </math></EquationSource> </InlineEquation> we have <Equation ID="Equ8"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_Equ8.gif" Format="GIF" Height="54" Rendition="HTML" Resolution="72" Type="Linedraw" Width="510" /> </MediaObject> <EquationSource Format="TEX">\(\begin{aligned} \lim \limits _{n\rightarrow \infty }\left[ T\left( \prod \limits _{k=1}^{n}e^{ \frac{x_{k}}{a_{n}\left( k+n\right) \left( k+2n\right) }},\prod \limits _{k=1}^{n}e^{\frac{y_{k}}{a_{n}\left( k+2n\right) \left( k+3n\right) } }\right) \right] ^{a_{n}}=e^{\left( \ln \frac{4}{3}\right) T\left( x,\textbf{ 1}\right) +\left( \ln 2\right) T\left( \textbf{1},y\right) }; \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <munder> <mo movablelimits="false">lim</mo> <mrow> <mi>n</mi> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </munder> <msup> <mfenced close="]" open="["> <mi>T</mi> <mfenced close=")" open="("> <munderover> <mo movablelimits="false">∏</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msup> <mi>e</mi> <mfrac> <msub> <mi>x</mi> <mi>k</mi> </msub> <mrow> <msub> <mi>a</mi> <mi>n</mi> </msub> <mfenced close=")" open="("> <mi>k</mi> <mo>+</mo> <mi>n</mi> </mfenced> <mfenced close=")" open="("> <mi>k</mi> <mo>+</mo> <mn>2</mn> <mi>n</mi> </mfenced> </mrow> </mfrac> </msup> <mo>,</mo> <munderover> <mo movablelimits="false">∏</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msup> <mi>e</mi> <mfrac> <msub> <mi>y</mi> <mi>k</mi> </msub> <mrow> <msub> <mi>a</mi> <mi>n</mi> </msub> <mfenced close=")" open="("> <mi>k</mi> <mo>+</mo> <mn>2</mn> <mi>n</mi> </mfenced> <mfenced close=")" open="("> <mi>k</mi> <mo>+</mo> <mn>3</mn> <mi>n</mi> </mfenced> </mrow> </mfrac> </msup> </mfenced> </mfenced> <msub> <mi>a</mi> <mi>n</mi> </msub> </msup> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mfenced close=")" open="("> <mo>ln</mo> <mfrac> <mn>4</mn> <mn>3</mn> </mfrac> </mfenced> <mi>T</mi> <mfenced close=")" open="("> <mi>x</mi> <mo>,</mo> <mn mathvariant="bold">1</mn> </mfenced> <mo>+</mo> <mfenced close=")" open="("> <mo>ln</mo> <mn>2</mn> </mfenced> <mi>T</mi> <mfenced close=")" open="("> <mn mathvariant="bold">1</mn> <mo>,</mo> <mi>y</mi> </mfenced> </mrow> </msup> <mo>;</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation><Equation ID="Equ9"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_Equ9.gif" Format="GIF" Height="60" Rendition="HTML" Resolution="72" Type="Linedraw" Width="419" /> </MediaObject> <EquationSource Format="TEX">\(\begin{aligned} \lim \limits _{n\rightarrow \infty }\left[ T\left( \prod \limits _{k=1}^{n}\cos \frac{x_{k}}{a_{n}\sqrt{n\left( n+k\right) }},\prod \limits _{k=1}^{n}\cos \frac{ky_{k}}{na_{n}\sqrt{n^{2}+k^{2}}}\right) \right] ^{na_{n}^{2}} \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <munder> <mo movablelimits="false">lim</mo> <mrow> <mi>n</mi> <mo stretchy="false">→</mo> <mi>∞</mi> </mrow> </munder> <msup> <mfenced close="]" open="["> <mi>T</mi> <mfenced close=")" open="("> <munderover> <mo movablelimits="false">∏</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <mo>cos</mo> <mfrac> <msub> <mi>x</mi> <mi>k</mi> </msub> <mrow> <msub> <mi>a</mi> <mi>n</mi> </msub> <msqrt> <mrow> <mi>n</mi> <mfenced close=")" open="("> <mi>n</mi> <mo>+</mo> <mi>k</mi> </mfenced> </mrow> </msqrt> </mrow> </mfrac> <mo>,</mo> <munderover> <mo movablelimits="false">∏</mo> <mrow> <mi>k</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <mo>cos</mo> <mfrac> <mrow> <mi>k</mi> <msub> <mi>y</mi> <mi>k</mi> </msub> </mrow> <mrow> <mi>n</mi> <msub> <mi>a</mi> <mi>n</mi> </msub> <msqrt> <mrow> <msup> <mi>n</mi> <mn>2</mn> </msup> <mo>+</mo> <msup> <mi>k</mi> <mn>2</mn> </msup> </mrow> </msqrt> </mrow> </mfrac> </mfenced> </mfenced> <mrow> <mi>n</mi> <msubsup> <mi>a</mi> <mrow> <mi>n</mi> </mrow> <mn>2</mn> </msubsup> </mrow> </msup> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation><Equation ID="Equ10"> <MediaObject> <ImageObject Color="BlackWhite" FileRef="13324_2024_1002_Article_Equ10.gif" Format="GIF" Height="30" Rendition="HTML" Resolution="72" Type="Linedraw" Width="185" /> </MediaObject> <EquationSource Format="TEX">\(\begin{aligned} =e^{-\frac{\left( \ln 2\right) T\left( x^{2},\textbf{1}\right) +\left( 1- \frac{\pi }{4}\right) T\left( \textbf{1},y^{2}\right) }{2}}. \end{aligned}\)</EquationSource> <EquationSource Format="MATHML"><math display="block"> <mrow> <mtable> <mtr> <mtd columnalign="right"> <mrow> <mo>=</mo> <msup> <mi>e</mi> <mrow> <mo>-</mo> <mfrac> <mrow> <mfenced close=")" open="("> <mo>ln</mo> <mn>2</mn> </mfenced> <mi>T</mi> <mfenced close=")" open="("> <msup> <mi>x</mi> <mn>2</mn> </msup> <mo>,</mo> <mn mathvariant="bold">1</mn> </mfenced> <mo>+</mo> <mfenced close=")" open="("> <mn>1</mn> <mo>-</mo> <mfrac> <mi>π</mi> <mn>4</mn> </mfrac> </mfenced> <mi>T</mi> <mfenced close=")" open="("> <mn mathvariant="bold">1</mn> <mo>,</mo> <msup> <mi>y</mi> <mn>2</mn> </msup> </mfenced> </mrow> <mn>2</mn> </mfrac> </mrow> </msup> <mo>.</mo> </mrow> </mtd> </mtr> </mtable> </mrow> </math></EquationSource> </Equation></p>

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New limits of the Lie product formula type in Banach algebras

  • Dumitru Popa

摘要

We find new limits of the Lie product formula type in Banach algebras with unit. Some sample results: Let X, Y, Z be Banach algebras with unit, \( \left( x_{n},y_{n}\right) _{n\in \mathbb {N}}\subset X\times Y\) x n , y n n N X × Y convergent sequences with \(\lim \nolimits _{n\rightarrow \infty }x_{n}=x\) lim n x n = x , \( \lim \nolimits _{n\rightarrow \infty }y_{n}=y\) lim n y n = y and \(T:X\times Y\rightarrow Z\) T : X × Y Z a continuous bilinear operator with \(T\left( \textbf{1},\textbf{1}\right) = \textbf{1}\) T 1 , 1 = 1 . Then for all sequences of natural numbers \(\left( a_{n}\right) _{n\in \mathbb {N}}\) a n n N with \(\lim \nolimits _{n\rightarrow \infty }a_{n}=\infty \) lim n a n = we have \(\begin{aligned} \lim \limits _{n\rightarrow \infty }\left[ T\left( \prod \limits _{k=1}^{n}e^{ \frac{x_{k}}{a_{n}\left( k+n\right) \left( k+2n\right) }},\prod \limits _{k=1}^{n}e^{\frac{y_{k}}{a_{n}\left( k+2n\right) \left( k+3n\right) } }\right) \right] ^{a_{n}}=e^{\left( \ln \frac{4}{3}\right) T\left( x,\textbf{ 1}\right) +\left( \ln 2\right) T\left( \textbf{1},y\right) }; \end{aligned}\) lim n T k = 1 n e x k a n k + n k + 2 n , k = 1 n e y k a n k + 2 n k + 3 n a n = e ln 4 3 T x , 1 + ln 2 T 1 , y ; \(\begin{aligned} \lim \limits _{n\rightarrow \infty }\left[ T\left( \prod \limits _{k=1}^{n}\cos \frac{x_{k}}{a_{n}\sqrt{n\left( n+k\right) }},\prod \limits _{k=1}^{n}\cos \frac{ky_{k}}{na_{n}\sqrt{n^{2}+k^{2}}}\right) \right] ^{na_{n}^{2}} \end{aligned}\) lim n T k = 1 n cos x k a n n n + k , k = 1 n cos k y k n a n n 2 + k 2 n a n 2 \(\begin{aligned} =e^{-\frac{\left( \ln 2\right) T\left( x^{2},\textbf{1}\right) +\left( 1- \frac{\pi }{4}\right) T\left( \textbf{1},y^{2}\right) }{2}}. \end{aligned}\) = e - ln 2 T x 2 , 1 + 1 - π 4 T 1 , y 2 2 .