In algebraic topology, the path space fibration over a based space (X, *) is a fibration of the form
Contents
where
The space
The path space fibration can be understood to be dual to the mapping cone. The reduced fibration is called the mapping fiber or, equivalently, the homotopy fiber.
Mapping path space
If ƒ:X→Y is any map, then the mapping path space Pƒ of ƒ is the pullback of
where
Note also ƒ is the composition
where the first map φ sends x to
If ƒ is a fibration to begin with, then
Moore's path space
By definition, a path in a space X is a map from the unit interval I to X. Again by definition, the product of two paths α, β such that α(1) = β(0) is the path β · α: I → X given by:
This product, in general, fails to be associative on the nose: (γ · β) · α ≠ γ · (β · α), as seen directly. One solution to this failure is to pass to homotopy classes: one has [(γ · β) · α ] = [γ · (β · α)]. Another solution is to work with paths of arbitrary length, leading to the notions of Moore's path space and Moore's path space fibration.
Given a based space (X, *), we let
An element f of this set has the unique extension
where p sends each f: [0, r] → X to f(r) and
Now, we define the product map:
by: for
This product is manifestly associative. In particular, with μ restricted to Ω'X × Ω'X, we have that Ω'X is a topological monoid (in the category of all spaces). Moreover, this monoid Ω'X acts on P'X through the original μ. In fact,