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Theorem sigaclci 34746
Description: A sigma-algebra is closed under countable intersections. Deduction version. The proof uses abrexct 23753 rather than abrexdom2jm 33086, and so does not require ax-ac 10518. (Contributed by Thierry Arnoux, 19-Sep-2016.) (Revised by Vincent Gonzalez, 19-Aug-2026.)
Assertion
Ref Expression
sigaclci (((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) ∧ (𝐴 ≼ ω ∧ 𝐴 ≠ ∅)) → ∩ 𝐴 ∈ 𝑆)

Proof of Theorem sigaclci
Dummy variables 𝑥 𝑦 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 isrnsigau 34741 . . . . . . . 8 (𝑆 ∈ ∪ ran sigAlgebra → (𝑆 ⊆ 𝒫 ∪ 𝑆 ∧ (∪ 𝑆 ∈ 𝑆 ∧ ∀𝑥 ∈ 𝑆 (∪ 𝑆 ∖ 𝑥) ∈ 𝑆 ∧ ∀𝑥 ∈ 𝒫 𝑆(𝑥 ≼ ω → ∪ 𝑥 ∈ 𝑆))))
21simprd 501 . . . . . . 7 (𝑆 ∈ ∪ ran sigAlgebra → (∪ 𝑆 ∈ 𝑆 ∧ ∀𝑥 ∈ 𝑆 (∪ 𝑆 ∖ 𝑥) ∈ 𝑆 ∧ ∀𝑥 ∈ 𝒫 𝑆(𝑥 ≼ ω → ∪ 𝑥 ∈ 𝑆)))
32simp2d 1161 . . . . . 6 (𝑆 ∈ ∪ ran sigAlgebra → ∀𝑥 ∈ 𝑆 (∪ 𝑆 ∖ 𝑥) ∈ 𝑆)
43adantr 486 . . . . 5 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ∀𝑥 ∈ 𝑆 (∪ 𝑆 ∖ 𝑥) ∈ 𝑆)
5 elpwi 4564 . . . . . . . . . . . 12 (𝐴 ∈ 𝒫 𝑆 → 𝐴 ⊆ 𝑆)
6 ssrexv 4001 . . . . . . . . . . . 12 (𝐴 ⊆ 𝑆 → (∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧) → ∃𝑧 ∈ 𝑆 𝑦 = (∪ 𝑆 ∖ 𝑧)))
75, 6syl 18 . . . . . . . . . . 11 (𝐴 ∈ 𝒫 𝑆 → (∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧) → ∃𝑧 ∈ 𝑆 𝑦 = (∪ 𝑆 ∖ 𝑧)))
87ss2abdv 4013 . . . . . . . . . 10 (𝐴 ∈ 𝒫 𝑆 → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ {𝑦 ∣ ∃𝑧 ∈ 𝑆 𝑦 = (∪ 𝑆 ∖ 𝑧)})
9 isrnsigau 34741 . . . . . . . . . . . . 13 (𝑆 ∈ ∪ ran sigAlgebra → (𝑆 ⊆ 𝒫 ∪ 𝑆 ∧ (∪ 𝑆 ∈ 𝑆 ∧ ∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 ∧ ∀𝑧 ∈ 𝒫 𝑆(𝑧 ≼ ω → ∪ 𝑧 ∈ 𝑆))))
109simprd 501 . . . . . . . . . . . 12 (𝑆 ∈ ∪ ran sigAlgebra → (∪ 𝑆 ∈ 𝑆 ∧ ∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 ∧ ∀𝑧 ∈ 𝒫 𝑆(𝑧 ≼ ω → ∪ 𝑧 ∈ 𝑆)))
1110simp2d 1161 . . . . . . . . . . 11 (𝑆 ∈ ∪ ran sigAlgebra → ∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆)
12 uniiunlem 4035 . . . . . . . . . . . 12 (∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 → (∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 ↔ {𝑦 ∣ ∃𝑧 ∈ 𝑆 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ 𝑆))
1311, 12syl 18 . . . . . . . . . . 11 (𝑆 ∈ ∪ ran sigAlgebra → (∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 ↔ {𝑦 ∣ ∃𝑧 ∈ 𝑆 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ 𝑆))
1411, 13mpbid 235 . . . . . . . . . 10 (𝑆 ∈ ∪ ran sigAlgebra → {𝑦 ∣ ∃𝑧 ∈ 𝑆 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ 𝑆)
158, 14sylan9ssr 3945 . . . . . . . . 9 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ 𝑆)
16 abrexexg 7962 . . . . . . . . . . 11 (𝐴 ∈ 𝒫 𝑆 → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ V)
17 elpwg 4560 . . . . . . . . . . 11 ({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ V → ({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝒫 𝑆 ↔ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ 𝑆))
1816, 17syl 18 . . . . . . . . . 10 (𝐴 ∈ 𝒫 𝑆 → ({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝒫 𝑆 ↔ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ 𝑆))
1918adantl 487 . . . . . . . . 9 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝒫 𝑆 ↔ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ⊆ 𝑆))
2015, 19mpbird 260 . . . . . . . 8 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝒫 𝑆)
212simp3d 1162 . . . . . . . . 9 (𝑆 ∈ ∪ ran sigAlgebra → ∀𝑥 ∈ 𝒫 𝑆(𝑥 ≼ ω → ∪ 𝑥 ∈ 𝑆))
2221adantr 486 . . . . . . . 8 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ∀𝑥 ∈ 𝒫 𝑆(𝑥 ≼ ω → ∪ 𝑥 ∈ 𝑆))
2320, 22jca 521 . . . . . . 7 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝒫 𝑆 ∧ ∀𝑥 ∈ 𝒫 𝑆(𝑥 ≼ ω → ∪ 𝑥 ∈ 𝑆)))
24 abrexct 23753 . . . . . . . . . 10 (𝐴 ≼ ω → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ≼ ω)
2524adantl 487 . . . . . . . . 9 ((𝐴 ∈ 𝒫 𝑆 ∧ 𝐴 ≼ ω) → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ≼ ω)
2625ex 418 . . . . . . . 8 (𝐴 ∈ 𝒫 𝑆 → (𝐴 ≼ ω → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ≼ ω))
2726adantl 487 . . . . . . 7 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → (𝐴 ≼ ω → {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ≼ ω))
28 breq1 5106 . . . . . . . . 9 (𝑥 = {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} → (𝑥 ≼ ω ↔ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ≼ ω))
29 unieq 4878 . . . . . . . . . 10 (𝑥 = {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} → ∪ 𝑥 = ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)})
3029eleq1d 2846 . . . . . . . . 9 (𝑥 = {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} → (∪ 𝑥 ∈ 𝑆 ↔ ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝑆))
3128, 30imbi12d 347 . . . . . . . 8 (𝑥 = {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} → ((𝑥 ≼ ω → ∪ 𝑥 ∈ 𝑆) ↔ ({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ≼ ω → ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝑆)))
3231rspcva 3575 . . . . . . 7 (({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝒫 𝑆 ∧ ∀𝑥 ∈ 𝒫 𝑆(𝑥 ≼ ω → ∪ 𝑥 ∈ 𝑆)) → ({𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ≼ ω → ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝑆))
3323, 27, 32sylsyld 62 . . . . . 6 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → (𝐴 ≼ ω → ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝑆))
345adantl 487 . . . . . . . 8 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → 𝐴 ⊆ 𝑆)
3511adantr 486 . . . . . . . 8 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆)
36 ssralv 4000 . . . . . . . 8 (𝐴 ⊆ 𝑆 → (∀𝑧 ∈ 𝑆 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 → ∀𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆))
3734, 35, 36sylc 66 . . . . . . 7 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ∀𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆)
38 dfiun2g 4988 . . . . . . 7 (∀𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 → ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) = ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)})
39 eleq1 2849 . . . . . . 7 (∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) = ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} → (∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 ↔ ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝑆))
4037, 38, 393syl 19 . . . . . 6 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → (∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 ↔ ∪ {𝑦 ∣ ∃𝑧 ∈ 𝐴 𝑦 = (∪ 𝑆 ∖ 𝑧)} ∈ 𝑆))
4133, 40sylibrd 262 . . . . 5 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → (𝐴 ≼ ω → ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆))
42 difeq2 4068 . . . . . . 7 (𝑥 = ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) → (∪ 𝑆 ∖ 𝑥) = (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)))
4342eleq1d 2846 . . . . . 6 (𝑥 = ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) → ((∪ 𝑆 ∖ 𝑥) ∈ 𝑆 ↔ (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆))
4443rspccv 3574 . . . . 5 (∀𝑥 ∈ 𝑆 (∪ 𝑆 ∖ 𝑥) ∈ 𝑆 → (∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧) ∈ 𝑆 → (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆))
454, 41, 44sylsyld 62 . . . 4 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → (𝐴 ≼ ω → (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆))
4645adantrd 497 . . 3 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ((𝐴 ≼ ω ∧ 𝐴 ≠ ∅) → (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆))
4746imp 412 . 2 (((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) ∧ (𝐴 ≼ ω ∧ 𝐴 ≠ ∅)) → (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆)
48 simpr 490 . . . . . 6 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → 𝐴 ∈ 𝒫 𝑆)
49 pwuni 4906 . . . . . . 7 𝑆 ⊆ 𝒫 ∪ 𝑆
505, 49sstrdi 3943 . . . . . 6 (𝐴 ∈ 𝒫 𝑆 → 𝐴 ⊆ 𝒫 ∪ 𝑆)
51 iundifdifd 33138 . . . . . 6 (𝐴 ⊆ 𝒫 ∪ 𝑆 → (𝐴 ≠ ∅ → ∩ 𝐴 = (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧))))
5248, 50, 513syl 19 . . . . 5 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → (𝐴 ≠ ∅ → ∩ 𝐴 = (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧))))
5352adantld 496 . . . 4 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ((𝐴 ≼ ω ∧ 𝐴 ≠ ∅) → ∩ 𝐴 = (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧))))
54 eleq1 2849 . . . 4 (∩ 𝐴 = (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) → (∩ 𝐴 ∈ 𝑆 ↔ (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆))
5553, 54syl6 36 . . 3 ((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) → ((𝐴 ≼ ω ∧ 𝐴 ≠ ∅) → (∩ 𝐴 ∈ 𝑆 ↔ (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆)))
5655imp 412 . 2 (((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) ∧ (𝐴 ≼ ω ∧ 𝐴 ≠ ∅)) → (∩ 𝐴 ∈ 𝑆 ↔ (∪ 𝑆 ∖ ∪ 𝑧 ∈ 𝐴 (∪ 𝑆 ∖ 𝑧)) ∈ 𝑆))
5747, 56mpbird 260 1 (((𝑆 ∈ ∪ ran sigAlgebra ∧ 𝐴 ∈ 𝒫 𝑆) ∧ (𝐴 ≼ ω ∧ 𝐴 ≠ ∅)) → ∩ 𝐴 ∈ 𝑆)
Colors of variables:    wff setvar class
This proof depends on syntax axioms:   → wi 4   ↔ wb 209   ∧ wa 401   ∧ w3a 1103   = wceq 1570   ∈ wcel 2145  {cab 2739   ≠ wne 2956  ∀wral 3077  ∃wrex 3087  Vcvv 3451   ∖ cdif 3896   ⊆ wss 3899  ∅c0 4279  𝒫 cpw 4557  ∪ cuni 4867  ∩ cint 4907  ∪ ciun 4951   class class class wbr 5103  ran crn 5652  ωcom 7866   ≼ cdom 8955  sigAlgebracsiga 34722
This proof depends on axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1828  ax-4 1842  ax-5 1943  ax-6 2000  ax-7 2041  ax-8 2147  ax-9 2155  ax-10 2178  ax-11 2194  ax-12 2213  ax-ext 2733  ax-rep 5232  ax-sep 5249  ax-nul 5260  ax-pow 5327  ax-pr 5391  ax-un 7740
This proof depends on definitions:  df-bi 210  df-an 402  df-or 862  df-3or 1104  df-3an 1105  df-tru 1573  df-fal 1583  df-ex 1813  df-nf 1817  df-sb 2100  df-mo 2565  df-eu 2595  df-clab 2740  df-cleq 2753  df-clel 2836  df-nfc 2910  df-ne 2957  df-ral 3078  df-rex 3088  df-rmo 3366  df-reu 3367  df-rab 3414  df-v 3453  df-sbc 3740  df-csb 3848  df-dif 3902  df-un 3904  df-in 3906  df-ss 3916  df-pss 3919  df-nul 4280  df-if 4483  df-pw 4559  df-sn 4585  df-pr 4587  df-op 4591  df-uni 4868  df-int 4908  df-iun 4953  df-iin 4954  df-br 5104  df-opab 5168  df-mpt 5187  df-tr 5213  df-id 5546  df-eprel 5551  df-po 5559  df-so 5560  df-fr 5604  df-se 5605  df-we 5606  df-xp 5657  df-rel 5658  df-cnv 5659  df-co 5660  df-dm 5661  df-rn 5662  df-res 5663  df-ima 5664  df-pred 6297  df-ord 6358  df-on 6359  df-lim 6360  df-suc 6361  df-iota 6487  df-fun 6533  df-fn 6534  df-f 6535  df-f1 6536  df-fo 6537  df-f1o 6538  df-fv 6539  df-isom 6540  df-riota 7369  df-ov 7415  df-oprab 7416  df-mpo 7417  df-om 7867  df-1st 7990  df-2nd 7991  df-frecs 8283  df-wrecs 8314  df-recs 8363  df-er 8701  df-map 8833  df-en 8958  df-dom 8959  df-card 10001  df-acn 10004  df-siga 34723
This theorem is used by:  sigapisys  34770
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