<p>Let <i>X</i> be a compact metric space. By <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq4.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="21" /> </InlineMediaObject> <EquationSource Format="TEX">\(2^X\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mn>2</mn> <mi>X</mi> </msup> </math></EquationSource> </InlineEquation> we denote the hyperspace of all closed and non-empty subsets of <i>X</i> endowed with the Hausdorff metric. Let <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq5.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="86" /> </InlineMediaObject> <EquationSource Format="TEX">\(f:X\rightarrow X\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>:</mo> <mi>X</mi> <mo stretchy="false">→</mo> <mi>X</mi> </mrow> </math></EquationSource> </InlineEquation> be a continuous function. We study some topological properties of the hyperspace <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="TEX">\(\omega (f)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ω</mi> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation>, the collection of all omega limits sets <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="52" /> </InlineMediaObject> <EquationSource Format="TEX">\(\omega (x,f)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ω</mi> <mo stretchy="false">(</mo> <mi>x</mi> <mo>,</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> with <InlineEquation ID="IEq8"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq8.gif" Format="GIF" Height="14" Rendition="HTML" Resolution="72" Type="Linedraw" Width="49" /> </InlineMediaObject> <EquationSource Format="TEX">\(x\in X\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>x</mi> <mo>∈</mo> <mi>X</mi> </mrow> </math></EquationSource> </InlineEquation>. We prove the following: (i) If <i>X</i> has no isolated points, then, for every continuous function <InlineEquation ID="IEq9"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq5.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="86" /> </InlineMediaObject> <EquationSource Format="TEX">\(f:X\rightarrow X\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>:</mo> <mi>X</mi> <mo stretchy="false">→</mo> <mi>X</mi> </mrow> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq10"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq10.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="123" /> </InlineMediaObject> <EquationSource Format="TEX">\({{\,\textrm{int}\,}}_{2^X}(\omega (f))=\varnothing \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mrow> <mspace width="0.166667em" /> <mtext>int</mtext> <mspace width="0.166667em" /> </mrow> <msup> <mn>2</mn> <mi>X</mi> </msup> </msub> <mrow> <mo stretchy="false">(</mo> <mi>ω</mi> <mrow> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> <mo stretchy="false">)</mo> </mrow> <mo>=</mo> <mi>∅</mi> </mrow> </math></EquationSource> </InlineEquation>. (ii) If <i>X</i> is a dendrite for which every arc contains a free arc and <InlineEquation ID="IEq11"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq5.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="86" /> </InlineMediaObject> <EquationSource Format="TEX">\(f:X\rightarrow X\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>:</mo> <mi>X</mi> <mo stretchy="false">→</mo> <mi>X</mi> </mrow> </math></EquationSource> </InlineEquation> is transitive, then the hyperspace <InlineEquation ID="IEq12"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="TEX">\(\omega (f)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ω</mi> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is totally disconnected. (iii) Let <InlineEquation ID="IEq13"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq13.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="29" /> </InlineMediaObject> <EquationSource Format="TEX">\(D_\infty \)</EquationSource> <EquationSource Format="MATHML"><math> <msub> <mi>D</mi> <mi>∞</mi> </msub> </math></EquationSource> </InlineEquation> be the Ważewski’s universal dendrite. Then there exists a transitive continuous function <InlineEquation ID="IEq14"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq14.gif" Format="GIF" Height="17" Rendition="HTML" Resolution="72" Type="Linedraw" Width="107" /> </InlineMediaObject> <EquationSource Format="TEX">\(f:D_\infty \rightarrow D_\infty \)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>f</mi> <mo>:</mo> <msub> <mi>D</mi> <mi>∞</mi> </msub> <mo stretchy="false">→</mo> <msub> <mi>D</mi> <mi>∞</mi> </msub> </mrow> </math></EquationSource> </InlineEquation> for which the hyperspace <InlineEquation ID="IEq15"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="TEX">\(\omega (f)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ω</mi> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> contains an arc; hence, <InlineEquation ID="IEq16"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2025_852_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="35" /> </InlineMediaObject> <EquationSource Format="TEX">\(\omega (f)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mi>ω</mi> <mo stretchy="false">(</mo> <mi>f</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is not totally disconnected.</p>

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The hyperspace \(\omega (f)\) when f is a transitive dendrite mapping

  • Jorge M. Martínez-Montejano,
  • Héctor Méndez,
  • Yajaida N. Velázquez-Inzunza

摘要

Let X be a compact metric space. By \(2^X\) 2 X we denote the hyperspace of all closed and non-empty subsets of X endowed with the Hausdorff metric. Let \(f:X\rightarrow X\) f : X X be a continuous function. We study some topological properties of the hyperspace \(\omega (f)\) ω ( f ) , the collection of all omega limits sets \(\omega (x,f)\) ω ( x , f ) with \(x\in X\) x X . We prove the following: (i) If X has no isolated points, then, for every continuous function \(f:X\rightarrow X\) f : X X , \({{\,\textrm{int}\,}}_{2^X}(\omega (f))=\varnothing \) int 2 X ( ω ( f ) ) = . (ii) If X is a dendrite for which every arc contains a free arc and \(f:X\rightarrow X\) f : X X is transitive, then the hyperspace \(\omega (f)\) ω ( f ) is totally disconnected. (iii) Let \(D_\infty \) D be the Ważewski’s universal dendrite. Then there exists a transitive continuous function \(f:D_\infty \rightarrow D_\infty \) f : D D for which the hyperspace \(\omega (f)\) ω ( f ) contains an arc; hence, \(\omega (f)\) ω ( f ) is not totally disconnected.