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Difference between revisions of "Path space"

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The space <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718401.png" /> of the fibre space <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718402.png" />, which is called the path fibre space. Here <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718403.png" /> is a [[Path-connected space|path-connected space]] with a distinguished point <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718404.png" />, <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718405.png" /> is the set of paths (cf. [[Path|Path]]) in <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718406.png" /> starting from <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718407.png" /> and <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718408.png" /> is the mapping associating to each path its end-point. Moreover, <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p0718409.png" /> is considered to have the compact-open topology. The fibre of this fibre space (which is a [[Serre fibration|Serre fibration]]) is the [[Loop space|loop space]] <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p07184010.png" /> — the set of all loops (cf. [[Loop|Loop]]) in <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p07184011.png" /> at <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p07184012.png" />. A path space can be contracted within itself to a point, so the homotopy groups <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p07184013.png" />, and the homotopy sequence of the path fibre space degenerates into the so-called Hurewicz isomorphisms:
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The space $E$ of the fibre space $(E,p,X)$, which is called the path fibre space. Here $X$ is a [[Path-connected space|path-connected space]] with a distinguished point $*$, $E$ is the set of paths (cf. [[Path|Path]]) in $X$ starting from $*$ and $p$ is the mapping associating to each path its end-point. Moreover, $E$ is considered to have the compact-open topology. The fibre of this fibre space (which is a [[Serre fibration|Serre fibration]]) is the [[Loop space|loop space]] $\Omega X$ — the set of all loops (cf. [[Loop|Loop]]) in $X$ at $*$. A path space can be contracted within itself to a point, so the homotopy groups $\pi_n(E)=0$, and the homotopy sequence of the path fibre space degenerates into the so-called Hurewicz isomorphisms:
  
<table class="eq" style="width:100%;"> <tr><td valign="top" style="width:94%;text-align:center;"><img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/p/p071/p071840/p07184014.png" /></td> </tr></table>
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$$\pi_n(\Omega X)\approx\pi_{n+1}(X).$$
  
  

Revision as of 15:58, 19 April 2014

The space $E$ of the fibre space $(E,p,X)$, which is called the path fibre space. Here $X$ is a path-connected space with a distinguished point $*$, $E$ is the set of paths (cf. Path) in $X$ starting from $*$ and $p$ is the mapping associating to each path its end-point. Moreover, $E$ is considered to have the compact-open topology. The fibre of this fibre space (which is a Serre fibration) is the loop space $\Omega X$ — the set of all loops (cf. Loop) in $X$ at $*$. A path space can be contracted within itself to a point, so the homotopy groups $\pi_n(E)=0$, and the homotopy sequence of the path fibre space degenerates into the so-called Hurewicz isomorphisms:

$$\pi_n(\Omega X)\approx\pi_{n+1}(X).$$


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References

[a1] E.H. Spanier, "Algebraic topology" , McGraw-Hill (1966) pp. 75ff, 99ff
How to Cite This Entry:
Path space. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Path_space&oldid=11316
This article was adapted from an original article by M.I. Voitsekhovskii (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article