<p>A topological space <i>X</i> is <i>Baire</i> if the Baire Category Theorem holds for <i>X</i>, i.e., the intersection of any sequence of open dense subsets of <i>X</i> is dense in <i>X</i>. One of the interesting problems for the space <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2024_799_Article_IEq1.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(B_1(X)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>B</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> of all Baire-one real-valued functions is the Banakh–Gabriyelyan problem of characterization of a topological space <i>X</i> for which the function space <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2024_799_Article_IEq2.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(B_1(X)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>B</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is Baire. In this paper, we solve this problem, namely, we obtain a characterization when <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2024_799_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(B_1(X)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>B</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is Baire for a topological space <i>X</i>. Also we prove that <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2024_799_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(B_1(X)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>B</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is Baire for any <InlineEquation ID="IEq5"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2024_799_Article_IEq5.gif" Format="GIF" Height="12" Rendition="HTML" Resolution="72" Type="Linedraw" Width="13" /> </InlineMediaObject> <EquationSource Format="TEX">\(\gamma \)</EquationSource> <EquationSource Format="MATHML"><math> <mi>γ</mi> </math></EquationSource> </InlineEquation>-space <i>X</i> and obtain a characterization of a topological space <i>X</i> for which <InlineEquation ID="IEq6"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2024_799_Article_IEq6.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(B_1(X)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>B</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is a Choquet space. This answers questions posed recently by Taras Banakh and Saak Gabriyelyan. We also conclude that it is consistent with ZFC that there is no uncountable separable metrizable space <i>X</i> such that <InlineEquation ID="IEq7"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="40879_2024_799_Article_IEq7.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="48" /> </InlineMediaObject> <EquationSource Format="TEX">\(B_1(X)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <msub> <mi>B</mi> <mn>1</mn> </msub> <mrow> <mo stretchy="false">(</mo> <mi>X</mi> <mo stretchy="false">)</mo> </mrow> </mrow> </math></EquationSource> </InlineEquation> is countable dense homogeneous.</p>

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Baire property of the space of Baire-one functions

  • Alexander V. Osipov

摘要

A topological space X is Baire if the Baire Category Theorem holds for X, i.e., the intersection of any sequence of open dense subsets of X is dense in X. One of the interesting problems for the space \(B_1(X)\) B 1 ( X ) of all Baire-one real-valued functions is the Banakh–Gabriyelyan problem of characterization of a topological space X for which the function space \(B_1(X)\) B 1 ( X ) is Baire. In this paper, we solve this problem, namely, we obtain a characterization when \(B_1(X)\) B 1 ( X ) is Baire for a topological space X. Also we prove that \(B_1(X)\) B 1 ( X ) is Baire for any \(\gamma \) γ -space X and obtain a characterization of a topological space X for which \(B_1(X)\) B 1 ( X ) is a Choquet space. This answers questions posed recently by Taras Banakh and Saak Gabriyelyan. We also conclude that it is consistent with ZFC that there is no uncountable separable metrizable space X such that \(B_1(X)\) B 1 ( X ) is countable dense homogeneous.