No.
If a product X × Y has the homotopy type of a finite–dimensional CW–complex, then each factor already has the homotopy type of a finite-dimensional CW–complex (in fact of dimension not larger than that of the product). Hence no counter–example can exist.
Let
f : X × Y → K, g : K → X × Y
be homotopy inverses, with K an n–dimensional CW–complex.
Fix
y0 ∈ Y and x0 ∈ X.
i_X : X → X × {y0} ⊂ X × Y,
a = f ∘ i_X : X → K (1)
r_X = π_X ∘ g : K → X (2)
(π_X denotes the projection X × Y → X.)
r_X ∘ a = π_X ∘ g ∘ f ∘ i_X ≃ π_X ∘ id_{X×Y} ∘ i_X = π_X ∘ i_X = id_X. (3)
So X is a retract up to homotopy of K; we say that X is dominated by an n–dimensional CW–complex.
If a space Z is dominated by an n–dimensional CW–complex, then Z itself has the homotopy type of an n–dimensional CW–complex.
Applying this to Z = X we conclude that X ≃ X′ where X′ is an n–dimensional CW–complex.
a′ = f ∘ j_Y : Y → K, r_Y = π_Y ∘ g : K → Y,
with r_Y ∘ a′ ≃ id_Y. Hence Y, too, is dominated by K and therefore has the homotopy type of an n–dimensional CW–complex.
• Both factors inherit finite dimensionality from the product; indeed
dim X, dim Y ≤ dim K.
• Because of this, there can be no space X that fails to be homotopy
equivalent to a finite-dimensional CW-complex while admitting a Y with
X × Y finite-dimensional up to homotopy.
Thus the answer to the original question is negative: whenever X × Y ≃ K with K finite-dimensional, both X and Y are themselves homotopy equivalent to finite-dimensional CW-complexes.
Was this answer helpful?
version: o3-2025-04-16
Status: UQ Validated
Validated: 8 months ago
Status: Needs Human Verification
Loading model reviews...
Loading reviews...