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单词 ExampleOfASpaceThatIsNotSemilocallySimplyConnected
释义

example of a space that is not semilocally simply connected


An example of a space that is not semilocally simply connected isthe following: Let

HR=n{(x,y)2|(x-12n)2+y2=(12n)2}

endowed with the subspace topology. Then (0,0) has no simply connectedneighborhoodMathworldPlanetmathPlanetmath. Indeed every neighborhood of (0,0) contains (ever diminshing)homotopically non-trivial loops. Furthermore these loops are homotopically non-trivial even when considered as loops in HR.

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The Hawaiian rings

It is essential in this example that HR is endowed with the topologyMathworldPlanetmathinduced by its inclusion in the plane. In contrast, the same set endowed withthe CW topology is just a bouquet of countably many circles and (as any CWcomplex) it is semilocaly simply connected.

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更新时间:2025/5/25 15:53:01