Metamath Proof Explorer


Theorem meaiininc

Description: Measures are continuous from above: if E is a nonincreasing sequence of measurable sets, and any of the sets has finite measure, then the measure of the intersection is the limit of the measures. This is Proposition 112C (f) of Fremlin1 p. 16. (Contributed by Glauco Siliprandi, 8-Apr-2021)

Ref Expression
Hypotheses meaiininc.f 𝑛 𝜑
meaiininc.m ( 𝜑𝑀 ∈ Meas )
meaiininc.n ( 𝜑𝑁 ∈ ℤ )
meaiininc.z 𝑍 = ( ℤ𝑁 )
meaiininc.e ( 𝜑𝐸 : 𝑍 ⟶ dom 𝑀 )
meaiininc.i ( ( 𝜑𝑛𝑍 ) → ( 𝐸 ‘ ( 𝑛 + 1 ) ) ⊆ ( 𝐸𝑛 ) )
meaiininc.k ( 𝜑𝐾 ∈ ( ℤ𝑁 ) )
meaiininc.r ( 𝜑 → ( 𝑀 ‘ ( 𝐸𝐾 ) ) ∈ ℝ )
meaiininc.s 𝑆 = ( 𝑛𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑛 ) ) )
Assertion meaiininc ( 𝜑𝑆 ⇝ ( 𝑀 𝑛𝑍 ( 𝐸𝑛 ) ) )

Proof

Step Hyp Ref Expression
1 meaiininc.f 𝑛 𝜑
2 meaiininc.m ( 𝜑𝑀 ∈ Meas )
3 meaiininc.n ( 𝜑𝑁 ∈ ℤ )
4 meaiininc.z 𝑍 = ( ℤ𝑁 )
5 meaiininc.e ( 𝜑𝐸 : 𝑍 ⟶ dom 𝑀 )
6 meaiininc.i ( ( 𝜑𝑛𝑍 ) → ( 𝐸 ‘ ( 𝑛 + 1 ) ) ⊆ ( 𝐸𝑛 ) )
7 meaiininc.k ( 𝜑𝐾 ∈ ( ℤ𝑁 ) )
8 meaiininc.r ( 𝜑 → ( 𝑀 ‘ ( 𝐸𝐾 ) ) ∈ ℝ )
9 meaiininc.s 𝑆 = ( 𝑛𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑛 ) ) )
10 nfv 𝑛 𝑖𝑍
11 1 10 nfan 𝑛 ( 𝜑𝑖𝑍 )
12 nfv 𝑛 ( 𝐸 ‘ ( 𝑖 + 1 ) ) ⊆ ( 𝐸𝑖 )
13 11 12 nfim 𝑛 ( ( 𝜑𝑖𝑍 ) → ( 𝐸 ‘ ( 𝑖 + 1 ) ) ⊆ ( 𝐸𝑖 ) )
14 eleq1w ( 𝑛 = 𝑖 → ( 𝑛𝑍𝑖𝑍 ) )
15 14 anbi2d ( 𝑛 = 𝑖 → ( ( 𝜑𝑛𝑍 ) ↔ ( 𝜑𝑖𝑍 ) ) )
16 fvoveq1 ( 𝑛 = 𝑖 → ( 𝐸 ‘ ( 𝑛 + 1 ) ) = ( 𝐸 ‘ ( 𝑖 + 1 ) ) )
17 fveq2 ( 𝑛 = 𝑖 → ( 𝐸𝑛 ) = ( 𝐸𝑖 ) )
18 16 17 sseq12d ( 𝑛 = 𝑖 → ( ( 𝐸 ‘ ( 𝑛 + 1 ) ) ⊆ ( 𝐸𝑛 ) ↔ ( 𝐸 ‘ ( 𝑖 + 1 ) ) ⊆ ( 𝐸𝑖 ) ) )
19 15 18 imbi12d ( 𝑛 = 𝑖 → ( ( ( 𝜑𝑛𝑍 ) → ( 𝐸 ‘ ( 𝑛 + 1 ) ) ⊆ ( 𝐸𝑛 ) ) ↔ ( ( 𝜑𝑖𝑍 ) → ( 𝐸 ‘ ( 𝑖 + 1 ) ) ⊆ ( 𝐸𝑖 ) ) ) )
20 13 19 6 chvarfv ( ( 𝜑𝑖𝑍 ) → ( 𝐸 ‘ ( 𝑖 + 1 ) ) ⊆ ( 𝐸𝑖 ) )
21 2fveq3 ( 𝑚 = 𝑖 → ( 𝑀 ‘ ( 𝐸𝑚 ) ) = ( 𝑀 ‘ ( 𝐸𝑖 ) ) )
22 21 cbvmptv ( 𝑚𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑚 ) ) ) = ( 𝑖𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑖 ) ) )
23 17 difeq2d ( 𝑛 = 𝑖 → ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑛 ) ) = ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑖 ) ) )
24 23 cbvmptv ( 𝑛𝑍 ↦ ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑛 ) ) ) = ( 𝑖𝑍 ↦ ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑖 ) ) )
25 fveq2 ( 𝑚 = 𝑖 → ( ( 𝑛𝑍 ↦ ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑛 ) ) ) ‘ 𝑚 ) = ( ( 𝑛𝑍 ↦ ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑛 ) ) ) ‘ 𝑖 ) )
26 25 cbviunv 𝑚𝑍 ( ( 𝑛𝑍 ↦ ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑛 ) ) ) ‘ 𝑚 ) = 𝑖𝑍 ( ( 𝑛𝑍 ↦ ( ( 𝐸𝐾 ) ∖ ( 𝐸𝑛 ) ) ) ‘ 𝑖 )
27 2 3 4 5 20 7 8 22 24 26 meaiininclem ( 𝜑 → ( 𝑚𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑚 ) ) ) ⇝ ( 𝑀 𝑖𝑍 ( 𝐸𝑖 ) ) )
28 2fveq3 ( 𝑛 = 𝑚 → ( 𝑀 ‘ ( 𝐸𝑛 ) ) = ( 𝑀 ‘ ( 𝐸𝑚 ) ) )
29 28 cbvmptv ( 𝑛𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑛 ) ) ) = ( 𝑚𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑚 ) ) )
30 9 29 eqtri 𝑆 = ( 𝑚𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑚 ) ) )
31 30 a1i ( 𝜑𝑆 = ( 𝑚𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑚 ) ) ) )
32 17 cbviinv 𝑛𝑍 ( 𝐸𝑛 ) = 𝑖𝑍 ( 𝐸𝑖 )
33 32 fveq2i ( 𝑀 𝑛𝑍 ( 𝐸𝑛 ) ) = ( 𝑀 𝑖𝑍 ( 𝐸𝑖 ) )
34 33 a1i ( 𝜑 → ( 𝑀 𝑛𝑍 ( 𝐸𝑛 ) ) = ( 𝑀 𝑖𝑍 ( 𝐸𝑖 ) ) )
35 31 34 breq12d ( 𝜑 → ( 𝑆 ⇝ ( 𝑀 𝑛𝑍 ( 𝐸𝑛 ) ) ↔ ( 𝑚𝑍 ↦ ( 𝑀 ‘ ( 𝐸𝑚 ) ) ) ⇝ ( 𝑀 𝑖𝑍 ( 𝐸𝑖 ) ) ) )
36 27 35 mpbird ( 𝜑𝑆 ⇝ ( 𝑀 𝑛𝑍 ( 𝐸𝑛 ) ) )