Attaching families of cells over a parameter space #
Let A be a subspace of a space Y, and let α i : P × ∂D^{k i} → A be continuous families of
attaching maps, parametrized by a space P. Attaching, over each p ∈ P, one disc D^{k i} along
each α i p gives the fiberwise adjunction space
(P × A) ∪_α ⨆ᵢ (P × D^{k i}),
the pushout in TopCat of (p, s) ↦ (p, α i (p, s)) along the inclusions
P × ∂D^{k i} → P × D^{k i} (TauCeti.fiberwiseCellAttachment). It lies over P
(TauCeti.fiberwiseCellAttachmentProj), and its points over p are those of the attachment
A ∪_{α p} ⨆ᵢ D^{k i}.
Characteristic families χ i : P × D^{k i} → Y restricting to α i on the boundary spheres induce
the comparison map (P × A) ∪_α ⨆ᵢ (P × D^{k i}) → P × Y over P
(TauCeti.fiberwiseCellComparison). These are the families of cell attachments met when the charts
of a Morse function at a critical level vary continuously with a parameter.
Two families χ₀ and χ₁ of characteristic maps are compared as in Milnor's Lemma 3.6, now over
P. Given self-maps h i of P × D^{k i} over P preserving P × ∂D^{k i}, and homotopies
K i : χ₁ i ≃ χ₀ i ∘ (p, h i) keeping P × ∂D^{k i} in A, the fiberwise reattachment map
(TauCeti.fiberwiseCellReattachment)
E : (P × A) ∪_{α₁} ⨆ᵢ (P × D^{k i}) → (P × A) ∪_{α₀} ⨆ᵢ (P × D^{k i})
is the identity on P × A, sends (p, x) in the i-th disc with ‖x‖ ≤ 1/2 to the point
(p, h i (p, 2x)) of the i-th disc, and sends (p, x) with 1/2 ≤ ‖x‖ to the point
(p, K i (2 - 2‖x‖, (p, x/‖x‖))) of P × A. It lies over P, and Φ₀ ∘ E is homotopic to Φ₁
relative to P × A through maps over P (TauCeti.fiberwiseCellReattachmentHomotopy), for the
comparison maps Φ₀ and Φ₁.
All of these constructions are natural in the parameter space: along a continuous map
g : P' → P, the attachments of the restricted families map to the original ones over g
(TauCeti.fiberwiseCellAttachmentMap), compatibly with the comparison maps and with the
reattachment maps (TauCeti.fiberwiseCellReattachment_comp_fiberwiseCellAttachmentMap) and with
the homotopies (TauCeti.fiberwiseCellReattachmentHomotopy_fiberwiseCellAttachmentMap). In
particular, for the inclusion of a subspace P' ⊆ P, restricting the data to P' gives the same
construction over P'.
References #
- J. Milnor, Morse Theory, Annals of Mathematics Studies 51, Princeton University Press, 1963, Lemma 3.6 and Remark 3.3.
The coproduct of the maps (p, s) ↦ (p, α i (p, s)) from P × ∂D^{k i} to P × A.
Instances For
The coproduct of the inclusions P × ∂D^{k i} → P × D^{k i}.
Instances For
The fiberwise adjunction space (P × A) ∪_α ⨆ᵢ (P × D^{k i}) of a family of attaching maps
α i : P × ∂D^{k i} → A: over each p, one disc D^{k i} is attached to A along each
α i (p, ·). It is the pushout in TopCat of TauCeti.fiberwiseAttachingMap α along
TauCeti.fiberwiseBoundaryInclusion (TauCeti.isPushout_fiberwiseCellAttachment).
Instances For
The inclusion of P × A into the fiberwise adjunction space.
Instances For
The family over P of characteristic maps P × D^{k i} → (P × A) ∪_α ⨆ᵢ (P × D^{k i}) of the
cells attached along α i.
Instances For
The fiberwise adjunction space is the pushout of the attaching maps along the boundary
inclusions, with the inclusion of P × A and the characteristic maps of the cells as its legs.
On the i-th summand, the coproduct of the attaching maps is (p, s) ↦ (p, α i (p, s)).
On the i-th summand, the coproduct of the boundary inclusions is the inclusion
P × ∂D^{k i} → P × D^{k i}.
On the boundary spheres, the characteristic maps of the cells are the attaching maps followed by
the inclusion of P × A.
A map on P × A and maps on the families of discs which agree along the attaching maps induce
a map out of the fiberwise adjunction space.
Instances For
Continuous maps out of the fiberwise adjunction space agree as soon as they agree on P × A
and on the cells.
Maps out of the fiberwise adjunction space are determined by their restrictions to P × A and
to the cells.
Every point of the fiberwise adjunction space lies in P × A or in a cell.
The map I × ((P × A) ∪_α ⨆ᵢ (P × D^{k i})) → W glued from L : I × (P × A) → W and maps
C i : I × (P × D^{k i}) → W that agree along the attaching maps: the form of
TauCeti.fiberwiseCellAttachmentDesc for homotopies out of the fiberwise adjunction space.
Instances For
The projection of the fiberwise adjunction space (P × A) ∪_α ⨆ᵢ (P × D^{k i}) to the parameter
space P.
Instances For
A property of the points of the fiberwise adjunction space holds as soon as it holds at the
points of P × A and of the cells.
The comparison map (P × A) ∪_α ⨆ᵢ (P × D^{k i}) → P × Y over P of a family of
characteristic maps χ i : P × D^{k i} → Y restricting to the attaching maps α i on the boundary
spheres: it is the inclusion on P × A and (p, x) ↦ (p, χ i (p, x)) on the i-th cell.
Instances For
The comparison map lies over P.
The fiberwise reattachment map
E : (P × A) ∪_{α₁} ⨆ᵢ (P × D^{k i}) → (P × A) ∪_{α₀} ⨆ᵢ (P × D^{k i}) of a family over P of
self-maps h i of the disc pairs (D^{k i}, ∂D^{k i}) and of homotopies
K i : χ₁ i ≃ χ₀ i ∘ (p, h i) of families of characteristic maps keeping the boundary spheres in
A. It is the identity on P × A; on the i-th family of discs it sends (p, x) to the point
(p, h i (p, 2x)) of the i-th cell when ‖x‖ ≤ 1/2, and to the point
(p, K i (2 - 2‖x‖, (p, x/‖x‖))) of P × A when 1/2 ≤ ‖x‖.
Instances For
The fiberwise reattachment map is the identity on P × A.
On the disc of radius 1/2 of the i-th cell over p, the fiberwise reattachment map is
x ↦ h i (p, 2x), read in the i-th cell over p.
Outside the disc of radius 1/2 of the i-th cell over p, the fiberwise reattachment map is
x ↦ K i (2 - 2‖x‖, (p, x/‖x‖)), read in P × A.
The fiberwise reattachment map lies over P.
Φ₀ ∘ E is homotopic to Φ₁ over P, relative to P × A. The homotopy from the fiberwise
reattachment map followed by the comparison map Φ₀ to the comparison map Φ₁. It fixes the
points of P × A, lies over P at all times
(TauCeti.fst_fiberwiseCellReattachmentHomotopy), and on the i-th cell it is K i read along
the straight-line homotopy TauCeti.TopCat.reattachmentPath in the cylinder I × D^{k i}.
Instances For
The homotopy from Φ₀ ∘ E to Φ₁ lies over P at all times.
The map of fiberwise adjunction spaces over a map g : P' → P of parameter spaces, for
families of attaching maps α' i (p, s) = α i (g p, s) restricted along g: it is g × id on
P' × A and on each family of discs. For the inclusion of a subspace P' ⊆ P, it includes the
attachment of the restricted families into the attachment over P.
Instances For
The map of fiberwise adjunction spaces lies over g.
The map of fiberwise adjunction spaces over the identity of P is the identity.
Maps of fiberwise adjunction spaces compose along composites of parameter maps.
Maps of fiberwise adjunction spaces compose along composites of parameter maps.
The map of fiberwise adjunction spaces over g intertwines the comparison maps of
characteristic families χ' i (p, x) = χ i (g p, x) restricted along g.
The fiberwise reattachment map is natural in the parameter space. Let g : P' → P be
continuous, and restrict along g the data of a fiberwise reattachment map over P: the attaching
maps, the self-maps h' i (p, x) = h i (g p, x) of the discs and the homotopies
K' i (t, (p, x)) = K i (t, (g p, x)). Then the reattachment map over P' of the restricted data,
followed by the map of fiberwise adjunction spaces over g, is the map over g followed by the
reattachment map over P.
The homotopy Φ₀ ∘ E ≃ Φ₁ is natural in the parameter space. For data restricted along a
continuous map g : P' → P, with K' i (t, (p, x)) = K i (t, (g p, x)), the homotopy over P
read on the image of the map of fiberwise adjunction spaces over g is the homotopy over P'
followed by g × id.