Path space (algebraic topology)

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In algebraic topology, a branch of mathematics, the path space [math]\displaystyle{ PX }[/math] of a based space [math]\displaystyle{ (X, *) }[/math] is the space that consists of all maps [math]\displaystyle{ f }[/math] from the interval [math]\displaystyle{ I = [0, 1] }[/math] to X such that [math]\displaystyle{ f(0) = * }[/math], called paths.[1] In other words, it is the mapping space from [math]\displaystyle{ (I, 0) }[/math] to [math]\displaystyle{ (X, *) }[/math]. The space [math]\displaystyle{ X^I }[/math] of all maps from [math]\displaystyle{ I }[/math] to X (free paths or just paths) is called the free path space of X.[2] The path space [math]\displaystyle{ PX }[/math] can then be viewed as the pullback of [math]\displaystyle{ X^I \to X, \, \chi \mapsto \chi(0) }[/math] along [math]\displaystyle{ * \hookrightarrow X }[/math].[1]

The natural map [math]\displaystyle{ PX \to X, \, \chi \to \chi(1) }[/math] is a fibration called the path space fibration.[3]

References

  1. 1.0 1.1 Martin Frankland, Math 527 - Homotopy Theory - Fiber sequences
  2. Davis & Kirk 2001, Definition 6.14.
  3. Davis & Kirk 2001, Theorem 6.15. 2.

Further reading