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zstone1 committed Dec 15, 2023
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104 changes: 0 additions & 104 deletions theories/cantor.v
Original file line number Diff line number Diff line change
Expand Up @@ -537,107 +537,3 @@ by exists f; rewrite -cstf; exact: cst_continuous.
Qed.

End alexandroff_hausdorff.

Section cantor_subspace.
Context {T : topologicalType} (A : set T).

Definition cantor_like_subspace :=
[/\ perfect_set A,
compact A,
hausdorff_space T &
totally_disconnected A].

Context a0 (Aa0 : A a0).

Let A' := PointedType (classicType_choiceType {x & A x}) (exist _ _ Aa0).
Let WA := @weak_topologicalType A' T (@projT1 _ A).
Lemma perfect_set_weak :
perfect_set A -> perfect_set [set: WA].
Proof.
move=> pftA; apply/perfectTP; case=> t At /=.
rewrite /open/=/wopen/=; apply/forallPNP => E oE.
case: (pselect (E t)); first last.
apply: contra_not; rewrite eqEsubset; case=> _ /(_ (existT _ _ At)).
exact.
case: pftA => clA lpA Et; have : A t by done.
rewrite -[a in a _]lpA => /(_ E) []; first exact: open_nbhs_nbhs.
move=> e [+] Ae Ee; apply: contra_neq_not.
rewrite eqEsubset; case=> /(_ (existT _ _ Ae) Ee) /= + _.
exact: EqdepFacts.eq_sigT_fst.
Qed.

Lemma compact_set_weak :
compact A -> compact [set: WA].
Proof.
move=> /compact_near_coveringP cptA; apply/ compact_near_coveringP.
move=> ? F /= P FF cvr; pose Q i x := if pselect (A x) is left Ax
then P i (existT _ _ Ax) else True.
have := (@cptA _ F Q FF); have FQ : forall x, A x -> \near x & F, Q F x.
move=> x Ax; have := cvr (existT _ _ Ax) I.
case; case=> E j [/= [? [[V oV /= <- /= Vx VE FJ EJ]]]].
exists (V, j); first by split => //; apply: open_nbhs_nbhs; split.
case=> /= z i [Vz ji]; rewrite /Q; case: (pselect _) => // Az.
by have := (EJ (existT _ _ Az, i)); apply; split => //; apply: VE.
move/(_ FQ); apply: filter_app; near=> z => + [r /= Ar _] => /(_ _ Ar).
by rewrite /Q; case (pselect _) => // Ar'; suff -> // : Ar = Ar'.
Unshelve. all: end_near. Qed.

Lemma totally_disconnected_weak :
totally_disconnected A -> totally_disconnected [set: WA].
Proof.
move=> tdA [x Ax] _; rewrite eqEsubset; split; first last.
by move=> ? ->; exact: connected_component_refl.
move=> [y Ay] [U [Ux _ ctU Uy]] => /=.
apply/eq_existT_curried; last by move=> ?.
have := tdA _ Ax; rewrite eqEsubset; case=> + _; apply.
exists (@projT1 T _ @` U); last by exists (existT _ _ Ay).
split; first by exists (existT _ _ Ax).
by move=> ? [[? ? ? <-]].
apply: connected_continuous_connected => //.
by apply: continuous_subspaceT; exact: weak_continuous.
Qed.

Lemma hausdorff_weak :
hausdorff_space T -> hausdorff_space WA.
Proof.
move=> hsdfK [p Ap] [q Aq] /= clstr.
apply/eq_existT_curried; last by move=> ?.
apply: hsdfK; move: clstr; rewrite ?cluster_cvgE /= => -[G PG [GtoQ psubG]].
exists (@projT1 T _ @ G); [exact: fmap_proper_filter|split].
apply: cvg_trans; first (apply:cvg_app; exact: GtoQ).
exact: weak_continuous.
move/(cvg_app (@projT1 T _)): psubG => /cvg_trans; apply.
exact: weak_continuous.
Qed.

Definition foo {R : realType} (P : set R) (P01 : P `<=` `[0%R,1%R]) : R -> R :=
0%R.
tvf@`P (wlog (tvf 1 = 1))

C --> [0,1] --> [0,1]
A A A
| | |
V | |
C <--> P ------> tvf @`P


mu (tvf @` P) = eps
mu (f @` P) = mu (((tvf + f)/2 - (tvf - f) /2) )

mu (f@` `[a,b]) =


Lemma cantor_like_subspaceP :
cantor_like_subspace -> cantor_like WA.
Proof.
case=> /perfect_set_weak ? /compact_set_weak ?.

Search (existT _ _ _ = existT _ _ _).
pose f x := if pselect (A x) is left Ax then existT _ _ Ax else existT _ _ Aa0.
have -> : [set existT _ _ Ax] = f @` [set x].
rewrite eqEsubset /f; split => z.
by move=> ->; exists x => //; case (pselect _) => // Ax';suff -> : Ax = Ax'.
by case => ? /= ->; case (pselect _) => // Ax'; suff -> : Ax = Ax'.

apply: connected_component_max.
End cantor_subspace.
63 changes: 0 additions & 63 deletions theories/charge.v
Original file line number Diff line number Diff line change
Expand Up @@ -478,69 +478,6 @@ Qed.

End positive_negative_set_realFieldType.

Section absolute_continuity.
Context {R : realType}.
Notation mu := (@lebesgue_measure R).

Lemma interval_measure0 A : is_interval A -> mu A = 0 -> is_subset1 A.
Proof.
Admitted.

Lemma measure0_disconnected A :
measurable A -> mu A = 0 -> totally_disconnected A.
Proof.
move=> mA A0 x Ax; rewrite eqEsubset; split; first last.
by move=> ? ->; exact: connected_component_refl.
move=> y [U /= [Ux UA /connected_intervalP ]] itvU.
have : mu U = 0.
apply/eqP; rewrite -measure_le0 //= -A0.
by apply: (le_measure); rewrite ?inE //; first exact: is_interval_measurable.
by move/(interval_measure0 itvU) => /[apply]; apply.
Qed.




Definition maps_null E (f : R -> R) :=
forall A, A `<=` E -> mu A = 0%:E -> mu (f @` A) = 0%:E.

Definition absolutely_continuous a b (f : R -> R) :=
[/\ {within `[a,b], continuous f },
bounded_variation a b f &
maps_null `[a,b] f
].

Lemma maps_null_total_variation (a b : R) f :
(a <= b)%R ->
absolutely_continuous a b f ->
maps_null `[a, b] (fine \o neg_tv a f).
Proof.
move=> ab [ctsf bdf] f0 A AE A0.

\int[pushforward mu mphi]_(y in (phi @` U)) f y
= \int[mu]_(x in phi^-1 (phi @` U)) (f \o phi) x.

0 = \int_(f@`A) id

integralD

Search measure (0%:E).

Local Notation TV := (@total_variation R).

Lemma absolute_continuity_cumulative a b (f : R -> R) :
absolutely_continuous a b f -> exists g h,
[/\ absolutely_continuous a b g,
absolutely_continuous a b h,
{in `[a,b] &, {homo g : x y / x <= y}},
{in `[a,b] &, {homo h : x y / x <= y}} &
f = g \- h
].
Proof.
case => ctsf bdf f0.

End absolute_continuity.

Section hahn_decomposition_lemma.
Context d (T : measurableType d) (R : realType).
Variables (nu : {charge set T -> \bar R}) (D : set T).
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8 changes: 0 additions & 8 deletions theories/topology.v
Original file line number Diff line number Diff line change
Expand Up @@ -3995,14 +3995,6 @@ suff : R `&` U = R by move: Rx => /[swap] <- [].
by apply: ctdR; [exists z|exists U|exists U].
Qed.

Lemma totally_disconnected_compact {T : topologicalType} :
hausdorff_space T ->
compact [set: T] ->
totally_disconnected [set: T] ->
zero_dimensional T.
Proof.
move=> hsdfT cmpT dctT x y xny.

Lemma totally_disconnected_cvg {T : topologicalType} (x : T) :
hausdorff_space T -> zero_dimensional T -> compact [set: T] ->
filter_from [set D : set T | D x /\ clopen D] id --> x.
Expand Down

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