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Description: Using the Axiom of Regularity in the form zfregfr , show that there are no infinite descending e. -chains. Proposition 7.34 of TakeutiZaring p. 44. (Contributed by NM, 26-Jan-2006) (Revised by Mario Carneiro, 22-Mar-2013)
| Ref | Expression | ||
|---|---|---|---|
| Assertion | noinfep | ⊢ ∃ 𝑥 ∈ ω ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) |
| Step | Hyp | Ref | Expression |
|---|---|---|---|
| 1 | omex | ⊢ ω ∈ V | |
| 2 | 1 | mptex | ⊢ ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ∈ V |
| 3 | 2 | rnex | ⊢ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ∈ V |
| 4 | zfregfr | ⊢ E Fr ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) | |
| 5 | ssid | ⊢ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ⊆ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) | |
| 6 | dmmptg | ⊢ ( ∀ 𝑤 ∈ ω ( 𝐹 ‘ 𝑤 ) ∈ V → dom ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) = ω ) | |
| 7 | fvexd | ⊢ ( 𝑤 ∈ ω → ( 𝐹 ‘ 𝑤 ) ∈ V ) | |
| 8 | 6 7 | mprg | ⊢ dom ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) = ω |
| 9 | peano1 | ⊢ ∅ ∈ ω | |
| 10 | 9 | ne0ii | ⊢ ω ≠ ∅ |
| 11 | 8 10 | eqnetri | ⊢ dom ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ≠ ∅ |
| 12 | dm0rn0 | ⊢ ( dom ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) = ∅ ↔ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) = ∅ ) | |
| 13 | 12 | necon3bii | ⊢ ( dom ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ≠ ∅ ↔ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ≠ ∅ ) |
| 14 | 11 13 | mpbi | ⊢ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ≠ ∅ |
| 15 | fri | ⊢ ( ( ( ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ∈ V ∧ E Fr ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ) ∧ ( ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ⊆ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ∧ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ≠ ∅ ) ) → ∃ 𝑦 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 ) | |
| 16 | 3 4 5 14 15 | mp4an | ⊢ ∃ 𝑦 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 |
| 17 | fvex | ⊢ ( 𝐹 ‘ 𝑤 ) ∈ V | |
| 18 | eqid | ⊢ ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) = ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) | |
| 19 | 17 18 | fnmpti | ⊢ ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) Fn ω |
| 20 | fvelrnb | ⊢ ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) Fn ω → ( 𝑦 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ↔ ∃ 𝑥 ∈ ω ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 ) ) | |
| 21 | 19 20 | ax-mp | ⊢ ( 𝑦 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ↔ ∃ 𝑥 ∈ ω ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 ) |
| 22 | peano2 | ⊢ ( 𝑥 ∈ ω → suc 𝑥 ∈ ω ) | |
| 23 | fveq2 | ⊢ ( 𝑤 = suc 𝑥 → ( 𝐹 ‘ 𝑤 ) = ( 𝐹 ‘ suc 𝑥 ) ) | |
| 24 | fvex | ⊢ ( 𝐹 ‘ suc 𝑥 ) ∈ V | |
| 25 | 23 18 24 | fvmpt | ⊢ ( suc 𝑥 ∈ ω → ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ suc 𝑥 ) = ( 𝐹 ‘ suc 𝑥 ) ) |
| 26 | 22 25 | syl | ⊢ ( 𝑥 ∈ ω → ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ suc 𝑥 ) = ( 𝐹 ‘ suc 𝑥 ) ) |
| 27 | fnfvelrn | ⊢ ( ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) Fn ω ∧ suc 𝑥 ∈ ω ) → ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ suc 𝑥 ) ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ) | |
| 28 | 19 22 27 | sylancr | ⊢ ( 𝑥 ∈ ω → ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ suc 𝑥 ) ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ) |
| 29 | 26 28 | eqeltrrd | ⊢ ( 𝑥 ∈ ω → ( 𝐹 ‘ suc 𝑥 ) ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ) |
| 30 | epel | ⊢ ( 𝑧 E 𝑦 ↔ 𝑧 ∈ 𝑦 ) | |
| 31 | eleq1 | ⊢ ( 𝑧 = ( 𝐹 ‘ suc 𝑥 ) → ( 𝑧 ∈ 𝑦 ↔ ( 𝐹 ‘ suc 𝑥 ) ∈ 𝑦 ) ) | |
| 32 | 30 31 | bitrid | ⊢ ( 𝑧 = ( 𝐹 ‘ suc 𝑥 ) → ( 𝑧 E 𝑦 ↔ ( 𝐹 ‘ suc 𝑥 ) ∈ 𝑦 ) ) |
| 33 | 32 | notbid | ⊢ ( 𝑧 = ( 𝐹 ‘ suc 𝑥 ) → ( ¬ 𝑧 E 𝑦 ↔ ¬ ( 𝐹 ‘ suc 𝑥 ) ∈ 𝑦 ) ) |
| 34 | df-nel | ⊢ ( ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 ↔ ¬ ( 𝐹 ‘ suc 𝑥 ) ∈ 𝑦 ) | |
| 35 | 33 34 | bitr4di | ⊢ ( 𝑧 = ( 𝐹 ‘ suc 𝑥 ) → ( ¬ 𝑧 E 𝑦 ↔ ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 ) ) |
| 36 | 35 | rspccv | ⊢ ( ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 → ( ( 𝐹 ‘ suc 𝑥 ) ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) → ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 ) ) |
| 37 | 29 36 | syl5com | ⊢ ( 𝑥 ∈ ω → ( ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 → ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 ) ) |
| 38 | fveq2 | ⊢ ( 𝑤 = 𝑥 → ( 𝐹 ‘ 𝑤 ) = ( 𝐹 ‘ 𝑥 ) ) | |
| 39 | fvex | ⊢ ( 𝐹 ‘ 𝑥 ) ∈ V | |
| 40 | 38 18 39 | fvmpt | ⊢ ( 𝑥 ∈ ω → ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = ( 𝐹 ‘ 𝑥 ) ) |
| 41 | eqeq1 | ⊢ ( ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 → ( ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = ( 𝐹 ‘ 𝑥 ) ↔ 𝑦 = ( 𝐹 ‘ 𝑥 ) ) ) | |
| 42 | 40 41 | syl5ibcom | ⊢ ( 𝑥 ∈ ω → ( ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 → 𝑦 = ( 𝐹 ‘ 𝑥 ) ) ) |
| 43 | neleq2 | ⊢ ( 𝑦 = ( 𝐹 ‘ 𝑥 ) → ( ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 ↔ ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) | |
| 44 | 43 | biimpd | ⊢ ( 𝑦 = ( 𝐹 ‘ 𝑥 ) → ( ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 → ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) |
| 45 | 42 44 | syl6 | ⊢ ( 𝑥 ∈ ω → ( ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 → ( ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 → ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) ) |
| 46 | 45 | com23 | ⊢ ( 𝑥 ∈ ω → ( ( 𝐹 ‘ suc 𝑥 ) ∉ 𝑦 → ( ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 → ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) ) |
| 47 | 37 46 | syldc | ⊢ ( ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 → ( 𝑥 ∈ ω → ( ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 → ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) ) |
| 48 | 47 | reximdvai | ⊢ ( ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 → ( ∃ 𝑥 ∈ ω ( ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ‘ 𝑥 ) = 𝑦 → ∃ 𝑥 ∈ ω ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) |
| 49 | 21 48 | biimtrid | ⊢ ( ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 → ( 𝑦 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) → ∃ 𝑥 ∈ ω ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) |
| 50 | 49 | com12 | ⊢ ( 𝑦 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) → ( ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 → ∃ 𝑥 ∈ ω ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) ) |
| 51 | 50 | rexlimiv | ⊢ ( ∃ 𝑦 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ∀ 𝑧 ∈ ran ( 𝑤 ∈ ω ↦ ( 𝐹 ‘ 𝑤 ) ) ¬ 𝑧 E 𝑦 → ∃ 𝑥 ∈ ω ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) ) |
| 52 | 16 51 | ax-mp | ⊢ ∃ 𝑥 ∈ ω ( 𝐹 ‘ suc 𝑥 ) ∉ ( 𝐹 ‘ 𝑥 ) |