The Moore-path replacement of a map #
For a continuous map p : E → B, the Moore-path replacement is the space
E' = MooreReplacement p of pairs (e, γ) of a point e ∈ E and a Moore path γ in B starting
at p e, with the endpoint map p' (e, γ) = γ.target.
p'has a transitive lifting function, given by concatenation: a pathδstarting atγ.targetlifts tos ↦ (e, γ · δ|[0, s]). Sop'is a Hurewicz fibration, whateverpis (TauCeti.MooreReplacement.isHurewiczFibration_endpoint).- The inclusion
E → E',e ↦ (e, const), is a map overBand a homotopy equivalence, with homotopy inverse the projection(e, γ) ↦ e: a path shrinks to its start (TauCeti.MooreReplacement.homotopyEquiv). - The fibre
F'ofp'overbcarries the strict right action(e, γ) · ω = (e, γ · ω)of the Moore loops atb, continuous in both variables. No choice of lifting function forpis involved.
When p itself has a lifting function Φ, transport F' → F, (e, γ) ↦ Φ (e, γ)(end), to
the fibre F of p over b is a homotopy equivalence, with homotopy inverse f ↦ (f, const)
(TauCeti.MooreLiftingFunction.transportHomotopyEquiv). When Φ is transitive, the Moore loops
act strictly on F by f · ω = Φ (f, ω)(end), and transport is strictly equivariant
(TauCeti.MooreLiftingFunction.IsTransitive.transport_act).
Main definitions #
TauCeti.MooreReplacement.endpoint p: the endpoint mapp' : E' → B.TauCeti.MooreReplacement.endpointLiftingFunction p: the transitive lifting function ofp'.TauCeti.MooreReplacement.Fiber p b: the fibreF'ofp'overb, with its right action ofMooreLoopSpace B b.TauCeti.MooreReplacement.Fiber.map h hh: the equivariant map of fibres induced by a maphoverB.TauCeti.MooreLiftingFunction.transport: transportF' → Falong a lifting function.
Main results #
TauCeti.MooreReplacement.isHurewiczFibration_endpoint:p'is a Hurewicz fibration.TauCeti.MooreReplacement.homotopyEquiv:E ≃ₕ E', by the inclusion overB.TauCeti.MooreLiftingFunction.transportHomotopyEquiv: transport is a homotopy equivalence.TauCeti.MooreLiftingFunction.IsTransitive.transport_act: transport is strictly equivariant.
References #
- J.-F. Barraud, M. Damian, V. Humilière, A. Oancea, Morse homology with differential graded coefficients, Progress in Mathematics 360, Birkhäuser, 2025, §7.1 (after Dold and Kamps).
The endpoint map and its lifting function #
The endpoint map p' : E' → B of the Moore-path replacement, (e, γ) ↦ γ.target.
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The lift of a path δ starting at the end point of (e, γ): the Moore path
s ↦ (e, γ · δ|[0, s]) in the replacement, of the length of δ.
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The transitive lifting function of the endpoint map of the Moore-path replacement:
concatenation, ((e, γ), δ) ↦ (s ↦ (e, γ · δ|[0, s])).
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The lifting function of the endpoint map is transitive.
The endpoint map of the Moore-path replacement is a Hurewicz fibration, whatever p is.
The inclusion and the projection #
The inclusion E → E', e ↦ (e, const), a map over B.
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The projection E' → E, (e, γ) ↦ e.
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The homotopy from incl ∘ proj to the identity of E', shrinking each path to its start:
(s, (e, γ)) ↦ (e, γ|[0, s · γ.length]).
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The inclusion E → E' is a homotopy equivalence, with homotopy inverse the projection.
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The fibre and the action of the Moore loops #
The fibre F' of the endpoint map over b: the pairs (e, γ) with γ ending at b.
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The underlying pair of a point of the fibre.
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The underlying pair of a point of the fibre is its value as an element of the subtype.
The point (e, γ) of the fibre, for a pair whose path ends at b.
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The right action of a Moore loop ω at b on the fibre: (e, γ) · ω = (e, γ · ω).
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The constant loop of length zero acts as the identity on the fibre.
The action is a right action: acting by ω * ω' is acting by ω, then by ω'.
The action is continuous in both variables.
The strict right action of the Moore loops at b on the fibre F', as a left action of
the opposite monoid.
Transport along a lifting function #
The action of a Moore loop ω at b on the fibre of p over b through a lifting function:
f · ω = Φ (f, ω)(end). It is a strict action when Φ is transitive.
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The action through a lifting function is continuous in both variables.
The unit loop acts trivially, for any lifting function: the lift of a path of length zero is constant.
For a transitive lifting function, the action of the Moore loops on the fibre is a right
action: acting by ω * ω' is acting by ω, then by ω'.
The strict right action of the Moore loops at b on the fibre of p over b, through a
transitive lifting function.
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The action through a transitive lifting function is continuous.
Transport along a lifting function, from the fibre F' of the Moore-path replacement to
the fibre F of p over b: (e, γ) ↦ Φ (e, γ)(end).
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Transport is strictly equivariant for the actions of the Moore loops, when the lifting function is transitive.
The inclusion of the fibre of p into the fibre F', f ↦ (f, const).
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The homotopy from the identity of F' to fiberIncl ∘ transport: at time s, lift the first
part γ|[0, u] of the path, u = s · γ.length, and keep the rest γ|[u, γ.length].
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Transport is a homotopy equivalence from the fibre F' of the Moore-path replacement to
the fibre of p, with homotopy inverse f ↦ (f, const).
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Naturality of the fibre in maps over the base #
The map of fibres of the Moore-path replacements induced by a map h : E → E' over B:
(e, γ) ↦ (h e, γ).
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The induced map of fibres commutes with the action of the Moore loops.
The identity induces the identity of fibres.
A composite of maps over B induces the composite of the maps of fibres.