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Theorem onsucsuccmpi 35818
Description: The successor of a successor ordinal number is a compact topology, proven without the Axiom of Regularity. (Contributed by Chen-Pang He, 18-Oct-2015.)
Hypothesis
Ref Expression
onsucsuccmpi.1 𝐴 ∈ On
Assertion
Ref Expression
onsucsuccmpi suc suc 𝐴 ∈ Comp

Proof of Theorem onsucsuccmpi
Dummy variables 𝑦 𝑧 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 onsucsuccmpi.1 . . . 4 𝐴 ∈ On
21onsuci 7820 . . 3 suc 𝐴 ∈ On
3 onsuctop 35808 . . 3 (suc 𝐴 ∈ On → suc suc 𝐴 ∈ Top)
42, 3ax-mp 5 . 2 suc suc 𝐴 ∈ Top
51onirri 6467 . . . . . . 7 ¬ 𝐴𝐴
61, 1onsucssi 7823 . . . . . . 7 (𝐴𝐴 ↔ suc 𝐴𝐴)
75, 6mtbi 322 . . . . . 6 ¬ suc 𝐴𝐴
8 sseq1 3999 . . . . . 6 (suc 𝐴 = 𝑦 → (suc 𝐴𝐴 𝑦𝐴))
97, 8mtbii 326 . . . . 5 (suc 𝐴 = 𝑦 → ¬ 𝑦𝐴)
10 elpwi 4601 . . . . . . 7 (𝑦 ∈ 𝒫 suc 𝐴𝑦 ⊆ suc 𝐴)
1110unissd 4909 . . . . . 6 (𝑦 ∈ 𝒫 suc 𝐴 𝑦 suc 𝐴)
121onunisuci 6474 . . . . . 6 suc 𝐴 = 𝐴
1311, 12sseqtrdi 4024 . . . . 5 (𝑦 ∈ 𝒫 suc 𝐴 𝑦𝐴)
149, 13nsyl 140 . . . 4 (suc 𝐴 = 𝑦 → ¬ 𝑦 ∈ 𝒫 suc 𝐴)
15 eldif 3950 . . . . . . 7 (𝑦 ∈ (𝒫 (suc 𝐴 ∪ {suc 𝐴}) ∖ 𝒫 suc 𝐴) ↔ (𝑦 ∈ 𝒫 (suc 𝐴 ∪ {suc 𝐴}) ∧ ¬ 𝑦 ∈ 𝒫 suc 𝐴))
16 elpwunsn 4679 . . . . . . 7 (𝑦 ∈ (𝒫 (suc 𝐴 ∪ {suc 𝐴}) ∖ 𝒫 suc 𝐴) → suc 𝐴𝑦)
1715, 16sylbir 234 . . . . . 6 ((𝑦 ∈ 𝒫 (suc 𝐴 ∪ {suc 𝐴}) ∧ ¬ 𝑦 ∈ 𝒫 suc 𝐴) → suc 𝐴𝑦)
1817ex 412 . . . . 5 (𝑦 ∈ 𝒫 (suc 𝐴 ∪ {suc 𝐴}) → (¬ 𝑦 ∈ 𝒫 suc 𝐴 → suc 𝐴𝑦))
19 df-suc 6360 . . . . . 6 suc suc 𝐴 = (suc 𝐴 ∪ {suc 𝐴})
2019pweqi 4610 . . . . 5 𝒫 suc suc 𝐴 = 𝒫 (suc 𝐴 ∪ {suc 𝐴})
2118, 20eleq2s 2843 . . . 4 (𝑦 ∈ 𝒫 suc suc 𝐴 → (¬ 𝑦 ∈ 𝒫 suc 𝐴 → suc 𝐴𝑦))
22 snelpwi 5433 . . . . 5 (suc 𝐴𝑦 → {suc 𝐴} ∈ 𝒫 𝑦)
23 snfi 9040 . . . . . . . 8 {suc 𝐴} ∈ Fin
2423jctr 524 . . . . . . 7 ({suc 𝐴} ∈ 𝒫 𝑦 → ({suc 𝐴} ∈ 𝒫 𝑦 ∧ {suc 𝐴} ∈ Fin))
25 elin 3956 . . . . . . 7 ({suc 𝐴} ∈ (𝒫 𝑦 ∩ Fin) ↔ ({suc 𝐴} ∈ 𝒫 𝑦 ∧ {suc 𝐴} ∈ Fin))
2624, 25sylibr 233 . . . . . 6 ({suc 𝐴} ∈ 𝒫 𝑦 → {suc 𝐴} ∈ (𝒫 𝑦 ∩ Fin))
272elexi 3486 . . . . . . . 8 suc 𝐴 ∈ V
2827unisn 4920 . . . . . . 7 {suc 𝐴} = suc 𝐴
2928eqcomi 2733 . . . . . 6 suc 𝐴 = {suc 𝐴}
30 unieq 4910 . . . . . . 7 (𝑧 = {suc 𝐴} → 𝑧 = {suc 𝐴})
3130rspceeqv 3625 . . . . . 6 (({suc 𝐴} ∈ (𝒫 𝑦 ∩ Fin) ∧ suc 𝐴 = {suc 𝐴}) → ∃𝑧 ∈ (𝒫 𝑦 ∩ Fin)suc 𝐴 = 𝑧)
3226, 29, 31sylancl 585 . . . . 5 ({suc 𝐴} ∈ 𝒫 𝑦 → ∃𝑧 ∈ (𝒫 𝑦 ∩ Fin)suc 𝐴 = 𝑧)
3322, 32syl 17 . . . 4 (suc 𝐴𝑦 → ∃𝑧 ∈ (𝒫 𝑦 ∩ Fin)suc 𝐴 = 𝑧)
3414, 21, 33syl56 36 . . 3 (𝑦 ∈ 𝒫 suc suc 𝐴 → (suc 𝐴 = 𝑦 → ∃𝑧 ∈ (𝒫 𝑦 ∩ Fin)suc 𝐴 = 𝑧))
3534rgen 3055 . 2 𝑦 ∈ 𝒫 suc suc 𝐴(suc 𝐴 = 𝑦 → ∃𝑧 ∈ (𝒫 𝑦 ∩ Fin)suc 𝐴 = 𝑧)
362onunisuci 6474 . . . 4 suc suc 𝐴 = suc 𝐴
3736eqcomi 2733 . . 3 suc 𝐴 = suc suc 𝐴
3837iscmp 23214 . 2 (suc suc 𝐴 ∈ Comp ↔ (suc suc 𝐴 ∈ Top ∧ ∀𝑦 ∈ 𝒫 suc suc 𝐴(suc 𝐴 = 𝑦 → ∃𝑧 ∈ (𝒫 𝑦 ∩ Fin)suc 𝐴 = 𝑧)))
394, 35, 38mpbir2an 708 1 suc suc 𝐴 ∈ Comp
Colors of variables: wff setvar class
Syntax hints:  ¬ wn 3  wi 4  wa 395   = wceq 1533  wcel 2098  wral 3053  wrex 3062  cdif 3937  cun 3938  cin 3939  wss 3940  𝒫 cpw 4594  {csn 4620   cuni 4899  Oncon0 6354  suc csuc 6356  Fincfn 8935  Topctop 22717  Compccmp 23212
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1789  ax-4 1803  ax-5 1905  ax-6 1963  ax-7 2003  ax-8 2100  ax-9 2108  ax-10 2129  ax-11 2146  ax-12 2163  ax-ext 2695  ax-sep 5289  ax-nul 5296  ax-pow 5353  ax-pr 5417  ax-un 7718
This theorem depends on definitions:  df-bi 206  df-an 396  df-or 845  df-3or 1085  df-3an 1086  df-tru 1536  df-fal 1546  df-ex 1774  df-nf 1778  df-sb 2060  df-mo 2526  df-eu 2555  df-clab 2702  df-cleq 2716  df-clel 2802  df-nfc 2877  df-ne 2933  df-ral 3054  df-rex 3063  df-rab 3425  df-v 3468  df-dif 3943  df-un 3945  df-in 3947  df-ss 3957  df-pss 3959  df-nul 4315  df-if 4521  df-pw 4596  df-sn 4621  df-pr 4623  df-op 4627  df-uni 4900  df-br 5139  df-opab 5201  df-mpt 5222  df-tr 5256  df-id 5564  df-eprel 5570  df-po 5578  df-so 5579  df-fr 5621  df-we 5623  df-xp 5672  df-rel 5673  df-cnv 5674  df-co 5675  df-dm 5676  df-rn 5677  df-ord 6357  df-on 6358  df-lim 6359  df-suc 6360  df-iota 6485  df-fun 6535  df-fn 6536  df-f 6537  df-f1 6538  df-fo 6539  df-f1o 6540  df-fv 6541  df-om 7849  df-1o 8461  df-en 8936  df-fin 8939  df-topgen 17388  df-top 22718  df-bases 22771  df-cmp 23213
This theorem is referenced by:  onsucsuccmp  35819
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