Theorem sdc 38082

Description: Strong dependent choice. Suppose we may choose an element of 𝐴 such that property 𝜓 holds, and suppose that if we have already chosen the first 𝑘 elements (represented here by a function from 1...𝑘 to 𝐴), we may choose another element so that all 𝑘 + 1 elements taken together have property 𝜓. Then there exists an infinite sequence of elements of 𝐴 such that the first 𝑛 terms of this sequence satisfy 𝜓 for all 𝑛. This theorem allows to construct infinite sequences where each term depends on all the previous terms in the sequence. (Contributed by Jeff Madsen, 2-Sep-2009.) (Proof shortened by Mario Carneiro, 3-Jun-2014.)

Hypotheses

Ref	Expression
sdc.1	⊢ 𝑍 = (ℤ≥‘𝑀)
sdc.2	⊢ (𝑔 = (𝑓 ↾ (𝑀...𝑛)) → (𝜓 ↔ 𝜒))
sdc.3	⊢ (𝑛 = 𝑀 → (𝜓 ↔ 𝜏))
sdc.4	⊢ (𝑛 = 𝑘 → (𝜓 ↔ 𝜃))
sdc.5	⊢ ((𝑔 = ℎ ∧ 𝑛 = (𝑘 + 1)) → (𝜓 ↔ 𝜎))
sdc.6	⊢ (𝜑 → 𝐴 ∈ 𝑉)
sdc.7	⊢ (𝜑 → 𝑀 ∈ ℤ)
sdc.8	⊢ (𝜑 → ∃𝑔(𝑔:{𝑀}⟶𝐴 ∧ 𝜏))
sdc.9	⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → ((𝑔:(𝑀...𝑘)⟶𝐴 ∧ 𝜃) → ∃ℎ(ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑔 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)))

Assertion

Ref	Expression
sdc	⊢ (𝜑 → ∃𝑓(𝑓:𝑍⟶𝐴 ∧ ∀𝑛 ∈ 𝑍 𝜒))

Distinct variable groups:   𝑓,𝑔,ℎ,𝑘,𝑛,𝐴   𝑓,𝑀,𝑔,ℎ,𝑘,𝑛   𝜒,𝑔   𝜓,𝑓,ℎ,𝑘   𝜎,𝑓,𝑔,𝑛   𝜑,𝑛   𝜃,𝑛   ℎ,𝑉   𝜏,ℎ,𝑘,𝑛   𝑓,𝑍,𝑔,ℎ,𝑘,𝑛   𝜑,𝑔,ℎ,𝑘

Allowed substitution hints:   𝜑(𝑓)   𝜓(𝑔,𝑛)   𝜒(𝑓,ℎ,𝑘,𝑛)   𝜃(𝑓,𝑔,ℎ,𝑘)   𝜏(𝑓,𝑔)   𝜎(ℎ,𝑘)   𝑉(𝑓,𝑔,𝑘,𝑛)

Proof of Theorem sdc

Dummy variables 𝑗 𝑥 𝑦 are mutually distinct and distinct from all other variables.

Step	Hyp	Ref	Expression
1		sdc.1	. 2 ⊢ 𝑍 = (ℤ≥‘𝑀)
2		sdc.2	. 2 ⊢ (𝑔 = (𝑓 ↾ (𝑀...𝑛)) → (𝜓 ↔ 𝜒))
3		sdc.3	. 2 ⊢ (𝑛 = 𝑀 → (𝜓 ↔ 𝜏))
4		sdc.4	. 2 ⊢ (𝑛 = 𝑘 → (𝜓 ↔ 𝜃))
5		sdc.5	. 2 ⊢ ((𝑔 = ℎ ∧ 𝑛 = (𝑘 + 1)) → (𝜓 ↔ 𝜎))
6		sdc.6	. 2 ⊢ (𝜑 → 𝐴 ∈ 𝑉)
7		sdc.7	. 2 ⊢ (𝜑 → 𝑀 ∈ ℤ)
8		sdc.8	. 2 ⊢ (𝜑 → ∃𝑔(𝑔:{𝑀}⟶𝐴 ∧ 𝜏))
9		sdc.9	. 2 ⊢ ((𝜑 ∧ 𝑘 ∈ 𝑍) → ((𝑔:(𝑀...𝑘)⟶𝐴 ∧ 𝜃) → ∃ℎ(ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑔 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)))
10		eqid 2737	. 2 ⊢ {𝑔 ∣ ∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓)} = {𝑔 ∣ ∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓)}
11		eqid 2737	. . . 4 ⊢ 𝑍 = 𝑍
12		oveq2 7369	. . . . . . . 8 ⊢ (𝑛 = 𝑘 → (𝑀...𝑛) = (𝑀...𝑘))
13	12	feq2d 6647	. . . . . . 7 ⊢ (𝑛 = 𝑘 → (𝑔:(𝑀...𝑛)⟶𝐴 ↔ 𝑔:(𝑀...𝑘)⟶𝐴))
14	13, 4	anbi12d 633	. . . . . 6 ⊢ (𝑛 = 𝑘 → ((𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓) ↔ (𝑔:(𝑀...𝑘)⟶𝐴 ∧ 𝜃)))
15	14	cbvrexvw 3217	. . . . 5 ⊢ (∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓) ↔ ∃𝑘 ∈ 𝑍 (𝑔:(𝑀...𝑘)⟶𝐴 ∧ 𝜃))
16	15	abbii 2804	. . . 4 ⊢ {𝑔 ∣ ∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓)} = {𝑔 ∣ ∃𝑘 ∈ 𝑍 (𝑔:(𝑀...𝑘)⟶𝐴 ∧ 𝜃)}
17		eqid 2737	. . . 4 ⊢ {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)} = {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)}
18	11, 16, 17	mpoeq123i 7437	. . 3 ⊢ (𝑗 ∈ 𝑍, 𝑓 ∈ {𝑔 ∣ ∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓)} ↦ {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)}) = (𝑗 ∈ 𝑍, 𝑓 ∈ {𝑔 ∣ ∃𝑘 ∈ 𝑍 (𝑔:(𝑀...𝑘)⟶𝐴 ∧ 𝜃)} ↦ {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)})
19		eqidd 2738	. . . 4 ⊢ (𝑗 = 𝑦 → {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)} = {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)})
20		eqeq1 2741	. . . . . . 7 ⊢ (𝑓 = 𝑥 → (𝑓 = (ℎ ↾ (𝑀...𝑘)) ↔ 𝑥 = (ℎ ↾ (𝑀...𝑘))))
21	20	3anbi2d 1444	. . . . . 6 ⊢ (𝑓 = 𝑥 → ((ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎) ↔ (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑥 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)))
22	21	rexbidv 3162	. . . . 5 ⊢ (𝑓 = 𝑥 → (∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎) ↔ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑥 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)))
23	22	abbidv 2803	. . . 4 ⊢ (𝑓 = 𝑥 → {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)} = {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑥 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)})
24	19, 23	cbvmpov 7456	. . 3 ⊢ (𝑗 ∈ 𝑍, 𝑓 ∈ {𝑔 ∣ ∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓)} ↦ {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)}) = (𝑦 ∈ 𝑍, 𝑥 ∈ {𝑔 ∣ ∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓)} ↦ {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑥 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)})
25	18, 24	eqtr3i 2762	. 2 ⊢ (𝑗 ∈ 𝑍, 𝑓 ∈ {𝑔 ∣ ∃𝑘 ∈ 𝑍 (𝑔:(𝑀...𝑘)⟶𝐴 ∧ 𝜃)} ↦ {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑓 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)}) = (𝑦 ∈ 𝑍, 𝑥 ∈ {𝑔 ∣ ∃𝑛 ∈ 𝑍 (𝑔:(𝑀...𝑛)⟶𝐴 ∧ 𝜓)} ↦ {ℎ ∣ ∃𝑘 ∈ 𝑍 (ℎ:(𝑀...(𝑘 + 1))⟶𝐴 ∧ 𝑥 = (ℎ ↾ (𝑀...𝑘)) ∧ 𝜎)})
26	1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 25	sdclem1 38081	1 ⊢ (𝜑 → ∃𝑓(𝑓:𝑍⟶𝐴 ∧ ∀𝑛 ∈ 𝑍 𝜒))

Syntax hints:   → wi 4   ↔ wb 206   ∧ wa 395   ∧ w3a 1087   = wceq 1542  ∃wex 1781   ∈ wcel 2114  {cab 2715  ∀wral 3052  ∃wrex 3062  {csn 4568   ↾ cres 5627  ⟶wf 6489  ‘cfv 6493  (class class class)co 7361   ∈ cmpo 7363  1c1 11033   + caddc 11035  ℤcz 12518  ℤ_≥cuz 12782  ...cfz 13455

This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1797  ax-4 1811  ax-5 1912  ax-6 1969  ax-7 2010  ax-8 2116  ax-9 2124  ax-10 2147  ax-11 2163  ax-12 2185  ax-ext 2709  ax-rep 5213  ax-sep 5232  ax-nul 5242  ax-pow 5303  ax-pr 5371  ax-un 7683  ax-inf2 9556  ax-dc 10362  ax-cnex 11088  ax-resscn 11089  ax-1cn 11090  ax-icn 11091  ax-addcl 11092  ax-addrcl 11093  ax-mulcl 11094  ax-mulrcl 11095  ax-mulcom 11096  ax-addass 11097  ax-mulass 11098  ax-distr 11099  ax-i2m1 11100  ax-1ne0 11101  ax-1rid 11102  ax-rnegex 11103  ax-rrecex 11104  ax-cnre 11105  ax-pre-lttri 11106  ax-pre-lttrn 11107  ax-pre-ltadd 11108  ax-pre-mulgt0 11109

This theorem depends on definitions:  df-bi 207  df-an 396  df-or 849  df-3or 1088  df-3an 1089  df-tru 1545  df-fal 1555  df-ex 1782  df-nf 1786  df-sb 2069  df-mo 2540  df-eu 2570  df-clab 2716  df-cleq 2729  df-clel 2812  df-nfc 2886  df-ne 2934  df-nel 3038  df-ral 3053  df-rex 3063  df-reu 3344  df-rab 3391  df-v 3432  df-sbc 3730  df-csb 3839  df-dif 3893  df-un 3895  df-in 3897  df-ss 3907  df-pss 3910  df-nul 4275  df-if 4468  df-pw 4544  df-sn 4569  df-pr 4571  df-op 4575  df-uni 4852  df-iun 4936  df-br 5087  df-opab 5149  df-mpt 5168  df-tr 5194  df-id 5520  df-eprel 5525  df-po 5533  df-so 5534  df-fr 5578  df-we 5580  df-xp 5631  df-rel 5632  df-cnv 5633  df-co 5634  df-dm 5635  df-rn 5636  df-res 5637  df-ima 5638  df-pred 6260  df-ord 6321  df-on 6322  df-lim 6323  df-suc 6324  df-iota 6449  df-fun 6495  df-fn 6496  df-f 6497  df-f1 6498  df-fo 6499  df-f1o 6500  df-fv 6501  df-riota 7318  df-ov 7364  df-oprab 7365  df-mpo 7366  df-om 7812  df-1st 7936  df-2nd 7937  df-frecs 8225  df-wrecs 8256  df-recs 8305  df-rdg 8343  df-1o 8399  df-er 8637  df-map 8769  df-en 8888  df-dom 8889  df-sdom 8890  df-pnf 11175  df-mnf 11176  df-xr 11177  df-ltxr 11178  df-le 11179  df-sub 11373  df-neg 11374  df-nn 12169  df-n0 12432  df-z 12519  df-uz 12783  df-fz 13456

This theorem is referenced by: (None)