<p>In the category <InlineEquation ID="IEq1"> <EquationSource Format="TEX">\(\textbf{V}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="bold">V</mi> </math></EquationSource> </InlineEquation> of unital archimedean vector lattices, several relatively recent results have brought closure to the notion of uniform completion: there are exactly four constructs worthy of the name uniform completion. In all cases completeness requires the convergence of uniformly Cauchy sequences; the completions are distinguished by the manner in which the convergence is regulated.<UnorderedList Mark="Bullet"> <ItemContent> <p>Ordinary uniform convergence is regulated by the canonical unit&#xa0;1.</p> </ItemContent> <ItemContent> <p>Inner relative uniform convergence, here termed <i>iru-convergence</i>, is regulated by an arbitrary positive element.</p> </ItemContent> <ItemContent> <p>Outer relative uniform convergence, here termed <i>oru-convergence</i>, is regulated by an arbitrary positive element of a vector lattice containing the given object as a sub-vector lattice.</p> </ItemContent> <ItemContent> <p><InlineEquation ID="IEq2"> <EquationSource Format="TEX">\(*\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow /> <mo>∗</mo> </mrow> </math></EquationSource> </InlineEquation>-<i>convergence</i> is equivalent to ordinary uniform convergence on certain specified quotients of the vector lattice.</p> </ItemContent> </UnorderedList> In each case the complete objects form a full monoreflective subcategory of <InlineEquation ID="IEq3"> <EquationSource Format="TEX">\(\textbf{V}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="bold">V</mi> </math></EquationSource> </InlineEquation>, denoted respectively <InlineEquation ID="IEq4"> <EquationSource Format="TEX">\(\textbf{ucV}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="bold">ucV</mi> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq5"> <EquationSource Format="TEX">\(\textbf{irucV}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="bold">irucV</mi> </math></EquationSource> </InlineEquation>, <InlineEquation ID="IEq6"> <EquationSource Format="TEX">\(\textbf{orucV}\)</EquationSource> <EquationSource Format="MATHML"><math> <mi mathvariant="bold">orucV</mi> </math></EquationSource> </InlineEquation>, and <InlineEquation ID="IEq7"> <EquationSource Format="TEX">\(\mathbf {*cV}\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mrow /> <mo>∗</mo> <mi mathvariant="bold">cV</mi> </mrow> </math></EquationSource> </InlineEquation>. In this article we survey these completions, comparing and contrasting them by means of a novel pointfree variant of the classical Yosida adjunction.</p>

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The four uniform completions of a unital archimedean vector lattice

  • Richard N. Ball,
  • Anthony W. Hager

摘要

In the category \(\textbf{V}\) V of unital archimedean vector lattices, several relatively recent results have brought closure to the notion of uniform completion: there are exactly four constructs worthy of the name uniform completion. In all cases completeness requires the convergence of uniformly Cauchy sequences; the completions are distinguished by the manner in which the convergence is regulated.

Ordinary uniform convergence is regulated by the canonical unit 1.

Inner relative uniform convergence, here termed iru-convergence, is regulated by an arbitrary positive element.

Outer relative uniform convergence, here termed oru-convergence, is regulated by an arbitrary positive element of a vector lattice containing the given object as a sub-vector lattice.

\(*\) -convergence is equivalent to ordinary uniform convergence on certain specified quotients of the vector lattice.

In each case the complete objects form a full monoreflective subcategory of \(\textbf{V}\) V , denoted respectively \(\textbf{ucV}\) ucV , \(\textbf{irucV}\) irucV , \(\textbf{orucV}\) orucV , and \(\mathbf {*cV}\) cV . In this article we survey these completions, comparing and contrasting them by means of a novel pointfree variant of the classical Yosida adjunction.