A lemma about ApproximatesLinearOn that needs FiniteDimensional #
In this file we prove that in a real vector space,
a function f that approximates a linear equivalence on a subset s
can be extended to a homeomorphism of the whole space.
This used to be the only lemma in Mathlib/Analysis/Calculus/Inverse
depending on FiniteDimensional, so it was moved to a new file when the original file got split.
theorem
ApproximatesLinearOn.exists_homeomorph_extension
{E : Type u_1}
[NormedAddCommGroup E]
[NormedSpace โ E]
{F : Type u_2}
[NormedAddCommGroup F]
[NormedSpace โ F]
[FiniteDimensional โ F]
{s : Set E}
{f : E โ F}
{f' : E โL[โ] F}
{c : NNReal}
(hf : ApproximatesLinearOn f (โf') s c)
(hc : Subsingleton E โจ lipschitzExtensionConstant F * c < โโf'.symmโโโปยน)
:
In a real vector space, a function f that approximates a linear equivalence on a subset s
can be extended to a homeomorphism of the whole space.