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Mirrors > Home > ILE Home > Th. List > tfri1d | GIF version |
Description: Principle of Transfinite
Recursion, part 1 of 3. Theorem 7.41(1) of
[TakeutiZaring] p. 47, with an
additional condition.
The condition is that 𝐺 is defined "everywhere", which is stated here as (𝐺‘𝑥) ∈ V. Alternately, ∀𝑥 ∈ On∀𝑓(𝑓 Fn 𝑥 → 𝑓 ∈ dom 𝐺) would suffice. Given a function 𝐺 satisfying that condition, we define a class 𝐴 of all "acceptable" functions. The final function we're interested in is the union 𝐹 = recs(𝐺) of them. 𝐹 is then said to be defined by transfinite recursion. The purpose of the 3 parts of this theorem is to demonstrate properties of 𝐹. In this first part we show that 𝐹 is a function whose domain is all ordinal numbers. (Contributed by Jim Kingdon, 4-May-2019.) (Revised by Mario Carneiro, 24-May-2019.) |
Ref | Expression |
---|---|
tfri1d.1 | ⊢ 𝐹 = recs(𝐺) |
tfri1d.2 | ⊢ (𝜑 → ∀𝑥(Fun 𝐺 ∧ (𝐺‘𝑥) ∈ V)) |
Ref | Expression |
---|---|
tfri1d | ⊢ (𝜑 → 𝐹 Fn On) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | eqid 2082 | . . . . . 6 ⊢ {𝑔 ∣ ∃𝑧 ∈ On (𝑔 Fn 𝑧 ∧ ∀𝑢 ∈ 𝑧 (𝑔‘𝑢) = (𝐺‘(𝑔 ↾ 𝑢)))} = {𝑔 ∣ ∃𝑧 ∈ On (𝑔 Fn 𝑧 ∧ ∀𝑢 ∈ 𝑧 (𝑔‘𝑢) = (𝐺‘(𝑔 ↾ 𝑢)))} | |
2 | 1 | tfrlem3 5960 | . . . . 5 ⊢ {𝑔 ∣ ∃𝑧 ∈ On (𝑔 Fn 𝑧 ∧ ∀𝑢 ∈ 𝑧 (𝑔‘𝑢) = (𝐺‘(𝑔 ↾ 𝑢)))} = {𝑓 ∣ ∃𝑥 ∈ On (𝑓 Fn 𝑥 ∧ ∀𝑦 ∈ 𝑥 (𝑓‘𝑦) = (𝐺‘(𝑓 ↾ 𝑦)))} |
3 | tfri1d.2 | . . . . 5 ⊢ (𝜑 → ∀𝑥(Fun 𝐺 ∧ (𝐺‘𝑥) ∈ V)) | |
4 | 2, 3 | tfrlemi14d 5982 | . . . 4 ⊢ (𝜑 → dom recs(𝐺) = On) |
5 | eqid 2082 | . . . . 5 ⊢ {𝑤 ∣ ∃𝑦 ∈ On (𝑤 Fn 𝑦 ∧ ∀𝑧 ∈ 𝑦 (𝑤‘𝑧) = (𝐺‘(𝑤 ↾ 𝑧)))} = {𝑤 ∣ ∃𝑦 ∈ On (𝑤 Fn 𝑦 ∧ ∀𝑧 ∈ 𝑦 (𝑤‘𝑧) = (𝐺‘(𝑤 ↾ 𝑧)))} | |
6 | 5 | tfrlem7 5966 | . . . 4 ⊢ Fun recs(𝐺) |
7 | 4, 6 | jctil 305 | . . 3 ⊢ (𝜑 → (Fun recs(𝐺) ∧ dom recs(𝐺) = On)) |
8 | df-fn 4935 | . . 3 ⊢ (recs(𝐺) Fn On ↔ (Fun recs(𝐺) ∧ dom recs(𝐺) = On)) | |
9 | 7, 8 | sylibr 132 | . 2 ⊢ (𝜑 → recs(𝐺) Fn On) |
10 | tfri1d.1 | . . 3 ⊢ 𝐹 = recs(𝐺) | |
11 | 10 | fneq1i 5024 | . 2 ⊢ (𝐹 Fn On ↔ recs(𝐺) Fn On) |
12 | 9, 11 | sylibr 132 | 1 ⊢ (𝜑 → 𝐹 Fn On) |
Colors of variables: wff set class |
Syntax hints: → wi 4 ∧ wa 102 ∀wal 1283 = wceq 1285 ∈ wcel 1434 {cab 2068 ∀wral 2349 ∃wrex 2350 Vcvv 2602 Oncon0 4126 dom cdm 4371 ↾ cres 4373 Fun wfun 4926 Fn wfn 4927 ‘cfv 4932 recscrecs 5953 |
This theorem was proved from axioms: ax-1 5 ax-2 6 ax-mp 7 ax-ia1 104 ax-ia2 105 ax-ia3 106 ax-in1 577 ax-in2 578 ax-io 663 ax-5 1377 ax-7 1378 ax-gen 1379 ax-ie1 1423 ax-ie2 1424 ax-8 1436 ax-10 1437 ax-11 1438 ax-i12 1439 ax-bndl 1440 ax-4 1441 ax-13 1445 ax-14 1446 ax-17 1460 ax-i9 1464 ax-ial 1468 ax-i5r 1469 ax-ext 2064 ax-coll 3901 ax-sep 3904 ax-pow 3956 ax-pr 3972 ax-un 4196 ax-setind 4288 |
This theorem depends on definitions: df-bi 115 df-3an 922 df-tru 1288 df-fal 1291 df-nf 1391 df-sb 1687 df-eu 1945 df-mo 1946 df-clab 2069 df-cleq 2075 df-clel 2078 df-nfc 2209 df-ne 2247 df-ral 2354 df-rex 2355 df-reu 2356 df-rab 2358 df-v 2604 df-sbc 2817 df-csb 2910 df-dif 2976 df-un 2978 df-in 2980 df-ss 2987 df-nul 3259 df-pw 3392 df-sn 3412 df-pr 3413 df-op 3415 df-uni 3610 df-iun 3688 df-br 3794 df-opab 3848 df-mpt 3849 df-tr 3884 df-id 4056 df-iord 4129 df-on 4131 df-suc 4134 df-xp 4377 df-rel 4378 df-cnv 4379 df-co 4380 df-dm 4381 df-rn 4382 df-res 4383 df-ima 4384 df-iota 4897 df-fun 4934 df-fn 4935 df-f 4936 df-f1 4937 df-fo 4938 df-f1o 4939 df-fv 4940 df-recs 5954 |
This theorem is referenced by: tfri2d 5985 tfri1 6014 rdgifnon 6028 rdgifnon2 6029 frecfnom 6050 |
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