<p>In this paper, we first introduce and study the notion of random Chebyshev centers. Further, based on the recently developed theory of stable sets, we introduce the notion of random complete normal structure so that we can prove the two deeper theorems: one of which states that random complete normal structure is equivalent to random normal structure for an <InlineEquation ID="IEq1"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11784_2025_1231_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(L^0\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>L</mi> <mn>0</mn> </msup> </math></EquationSource> </InlineEquation>-convexly compact set in a complete random normed module; the other of which states that if <i>G</i> is an <InlineEquation ID="IEq2"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11784_2025_1231_Article_IEq1.gif" Format="GIF" Height="16" Rendition="HTML" Resolution="72" Type="Linedraw" Width="19" /> </InlineMediaObject> <EquationSource Format="TEX">\(L^0\)</EquationSource> <EquationSource Format="MATHML"><math> <msup> <mi>L</mi> <mn>0</mn> </msup> </math></EquationSource> </InlineEquation>-convexly compact subset with random normal structure of a complete random normed module, then every commutative family of nonexpansive mappings from <i>G</i> to <i>G</i> has a common fixed point. We also consider the fixed point problems for isometric mappings in complete random normed modules. Finally, as applications of the fixed point theorems established in random normed modules, when the measurable selection theorems fail to work, we can still prove that a commutative family of strong random nonexpansive operators from <InlineEquation ID="IEq3"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11784_2025_1231_Article_IEq3.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="104" /> </InlineMediaObject> <EquationSource Format="TEX">\((\Omega ,\mathcal {F},P)\times C\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="normal">Ω</mi> <mo>,</mo> <mi mathvariant="script">F</mi> <mo>,</mo> <mi>P</mi> <mo stretchy="false">)</mo> <mo>×</mo> <mi>C</mi> </mrow> </math></EquationSource> </InlineEquation> to <i>C</i> has a common random fixed point, where <InlineEquation ID="IEq4"> <InlineMediaObject> <ImageObject Color="BlackWhite" FileRef="11784_2025_1231_Article_IEq4.gif" Format="GIF" Height="19" Rendition="HTML" Resolution="72" Type="Linedraw" Width="68" /> </InlineMediaObject> <EquationSource Format="TEX">\((\Omega ,\mathcal {F},P)\)</EquationSource> <EquationSource Format="MATHML"><math> <mrow> <mo stretchy="false">(</mo> <mi mathvariant="normal">Ω</mi> <mo>,</mo> <mi mathvariant="script">F</mi> <mo>,</mo> <mi>P</mi> <mo stretchy="false">)</mo> </mrow> </math></EquationSource> </InlineEquation> is a probability space and <i>C</i> is a weakly compact convex subset with normal structure of a Banach space.</p>

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Common fixed point theorems for a commutative family of nonexpansive mappings in complete random normed modules

  • Xiaohuan Mu,
  • Qiang Tu,
  • Tiexin Guo,
  • Hong-Kun Xu

摘要

In this paper, we first introduce and study the notion of random Chebyshev centers. Further, based on the recently developed theory of stable sets, we introduce the notion of random complete normal structure so that we can prove the two deeper theorems: one of which states that random complete normal structure is equivalent to random normal structure for an \(L^0\) L 0 -convexly compact set in a complete random normed module; the other of which states that if G is an \(L^0\) L 0 -convexly compact subset with random normal structure of a complete random normed module, then every commutative family of nonexpansive mappings from G to G has a common fixed point. We also consider the fixed point problems for isometric mappings in complete random normed modules. Finally, as applications of the fixed point theorems established in random normed modules, when the measurable selection theorems fail to work, we can still prove that a commutative family of strong random nonexpansive operators from \((\Omega ,\mathcal {F},P)\times C\) ( Ω , F , P ) × C to C has a common random fixed point, where \((\Omega ,\mathcal {F},P)\) ( Ω , F , P ) is a probability space and C is a weakly compact convex subset with normal structure of a Banach space.