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Mirrors > Home > MPE Home > Th. List > tgclb | Structured version Visualization version GIF version |
Description: The property tgcl 20584 can be reversed: if the topology generated by 𝐵 is actually a topology, then 𝐵 must be a topological basis. This yields an alternative definition of TopBases. (Contributed by Mario Carneiro, 2-Sep-2015.) |
Ref | Expression |
---|---|
tgclb | ⊢ (𝐵 ∈ TopBases ↔ (topGen‘𝐵) ∈ Top) |
Step | Hyp | Ref | Expression |
---|---|---|---|
1 | tgcl 20584 | . 2 ⊢ (𝐵 ∈ TopBases → (topGen‘𝐵) ∈ Top) | |
2 | 0opn 20534 | . . . . . . . . . 10 ⊢ ((topGen‘𝐵) ∈ Top → ∅ ∈ (topGen‘𝐵)) | |
3 | 2 | elfvexd 6132 | . . . . . . . . 9 ⊢ ((topGen‘𝐵) ∈ Top → 𝐵 ∈ V) |
4 | bastg 20581 | . . . . . . . . 9 ⊢ (𝐵 ∈ V → 𝐵 ⊆ (topGen‘𝐵)) | |
5 | 3, 4 | syl 17 | . . . . . . . 8 ⊢ ((topGen‘𝐵) ∈ Top → 𝐵 ⊆ (topGen‘𝐵)) |
6 | 5 | sselda 3568 | . . . . . . 7 ⊢ (((topGen‘𝐵) ∈ Top ∧ 𝑥 ∈ 𝐵) → 𝑥 ∈ (topGen‘𝐵)) |
7 | 5 | sselda 3568 | . . . . . . 7 ⊢ (((topGen‘𝐵) ∈ Top ∧ 𝑦 ∈ 𝐵) → 𝑦 ∈ (topGen‘𝐵)) |
8 | 6, 7 | anim12dan 878 | . . . . . 6 ⊢ (((topGen‘𝐵) ∈ Top ∧ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵)) → (𝑥 ∈ (topGen‘𝐵) ∧ 𝑦 ∈ (topGen‘𝐵))) |
9 | inopn 20529 | . . . . . . 7 ⊢ (((topGen‘𝐵) ∈ Top ∧ 𝑥 ∈ (topGen‘𝐵) ∧ 𝑦 ∈ (topGen‘𝐵)) → (𝑥 ∩ 𝑦) ∈ (topGen‘𝐵)) | |
10 | 9 | 3expb 1258 | . . . . . 6 ⊢ (((topGen‘𝐵) ∈ Top ∧ (𝑥 ∈ (topGen‘𝐵) ∧ 𝑦 ∈ (topGen‘𝐵))) → (𝑥 ∩ 𝑦) ∈ (topGen‘𝐵)) |
11 | 8, 10 | syldan 486 | . . . . 5 ⊢ (((topGen‘𝐵) ∈ Top ∧ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵)) → (𝑥 ∩ 𝑦) ∈ (topGen‘𝐵)) |
12 | tg2 20580 | . . . . . 6 ⊢ (((𝑥 ∩ 𝑦) ∈ (topGen‘𝐵) ∧ 𝑧 ∈ (𝑥 ∩ 𝑦)) → ∃𝑤 ∈ 𝐵 (𝑧 ∈ 𝑤 ∧ 𝑤 ⊆ (𝑥 ∩ 𝑦))) | |
13 | 12 | ralrimiva 2949 | . . . . 5 ⊢ ((𝑥 ∩ 𝑦) ∈ (topGen‘𝐵) → ∀𝑧 ∈ (𝑥 ∩ 𝑦)∃𝑤 ∈ 𝐵 (𝑧 ∈ 𝑤 ∧ 𝑤 ⊆ (𝑥 ∩ 𝑦))) |
14 | 11, 13 | syl 17 | . . . 4 ⊢ (((topGen‘𝐵) ∈ Top ∧ (𝑥 ∈ 𝐵 ∧ 𝑦 ∈ 𝐵)) → ∀𝑧 ∈ (𝑥 ∩ 𝑦)∃𝑤 ∈ 𝐵 (𝑧 ∈ 𝑤 ∧ 𝑤 ⊆ (𝑥 ∩ 𝑦))) |
15 | 14 | ralrimivva 2954 | . . 3 ⊢ ((topGen‘𝐵) ∈ Top → ∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ∀𝑧 ∈ (𝑥 ∩ 𝑦)∃𝑤 ∈ 𝐵 (𝑧 ∈ 𝑤 ∧ 𝑤 ⊆ (𝑥 ∩ 𝑦))) |
16 | isbasis2g 20563 | . . . 4 ⊢ (𝐵 ∈ V → (𝐵 ∈ TopBases ↔ ∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ∀𝑧 ∈ (𝑥 ∩ 𝑦)∃𝑤 ∈ 𝐵 (𝑧 ∈ 𝑤 ∧ 𝑤 ⊆ (𝑥 ∩ 𝑦)))) | |
17 | 3, 16 | syl 17 | . . 3 ⊢ ((topGen‘𝐵) ∈ Top → (𝐵 ∈ TopBases ↔ ∀𝑥 ∈ 𝐵 ∀𝑦 ∈ 𝐵 ∀𝑧 ∈ (𝑥 ∩ 𝑦)∃𝑤 ∈ 𝐵 (𝑧 ∈ 𝑤 ∧ 𝑤 ⊆ (𝑥 ∩ 𝑦)))) |
18 | 15, 17 | mpbird 246 | . 2 ⊢ ((topGen‘𝐵) ∈ Top → 𝐵 ∈ TopBases) |
19 | 1, 18 | impbii 198 | 1 ⊢ (𝐵 ∈ TopBases ↔ (topGen‘𝐵) ∈ Top) |
Colors of variables: wff setvar class |
Syntax hints: ↔ wb 195 ∧ wa 383 ∈ wcel 1977 ∀wral 2896 ∃wrex 2897 Vcvv 3173 ∩ cin 3539 ⊆ wss 3540 ∅c0 3874 ‘cfv 5804 topGenctg 15921 Topctop 20517 TopBasesctb 20520 |
This theorem was proved from axioms: ax-mp 5 ax-1 6 ax-2 7 ax-3 8 ax-gen 1713 ax-4 1728 ax-5 1827 ax-6 1875 ax-7 1922 ax-8 1979 ax-9 1986 ax-10 2006 ax-11 2021 ax-12 2034 ax-13 2234 ax-ext 2590 ax-sep 4709 ax-nul 4717 ax-pow 4769 ax-pr 4833 ax-un 6847 |
This theorem depends on definitions: df-bi 196 df-or 384 df-an 385 df-3an 1033 df-tru 1478 df-ex 1696 df-nf 1701 df-sb 1868 df-eu 2462 df-mo 2463 df-clab 2597 df-cleq 2603 df-clel 2606 df-nfc 2740 df-ne 2782 df-ral 2901 df-rex 2902 df-rab 2905 df-v 3175 df-sbc 3403 df-dif 3543 df-un 3545 df-in 3547 df-ss 3554 df-nul 3875 df-if 4037 df-pw 4110 df-sn 4126 df-pr 4128 df-op 4132 df-uni 4373 df-br 4584 df-opab 4644 df-mpt 4645 df-id 4953 df-xp 5044 df-rel 5045 df-cnv 5046 df-co 5047 df-dm 5048 df-iota 5768 df-fun 5806 df-fv 5812 df-topgen 15927 df-top 20521 df-bases 20522 |
This theorem is referenced by: bastop2 20609 iocpnfordt 20829 icomnfordt 20830 iooordt 20831 tgcn 20866 tgcnp 20867 2ndcctbss 21068 2ndcomap 21071 dis2ndc 21073 flftg 21610 met2ndci 22137 xrtgioo 22417 topfneec 31520 |
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