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Theorem isga 18897
Description: The predicate "is a (left) group action". The group 𝐺 is said to act on the base set 𝑌 of the action, which is not assumed to have any special properties. There is a related notion of right group action, but as the Wikipedia article explains, it is not mathematically interesting. The way actions are usually thought of is that each element 𝑔 of 𝐺 is a permutation of the elements of 𝑌 (see gapm 18912). Since group theory was classically about symmetry groups, it is therefore likely that the notion of group action was useful even in early group theory. (Contributed by Jeff Hankins, 10-Aug-2009.) (Revised by Mario Carneiro, 13-Jan-2015.)
Hypotheses
Ref Expression
isga.1 𝑋 = (Base‘𝐺)
isga.2 + = (+g𝐺)
isga.3 0 = (0g𝐺)
Assertion
Ref Expression
isga ( ∈ (𝐺 GrpAct 𝑌) ↔ ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) ∧ ( :(𝑋 × 𝑌)⟶𝑌 ∧ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥))))))
Distinct variable groups:   𝑥,𝑦,𝑧,𝐺   𝑦,𝑋,𝑧   𝑥,𝑌,𝑦,𝑧   𝑥, ,𝑦,𝑧
Allowed substitution hints:   + (𝑥,𝑦,𝑧)   𝑋(𝑥)   0 (𝑥,𝑦,𝑧)

Proof of Theorem isga
Dummy variables 𝑔 𝑏 𝑚 𝑠 are mutually distinct and distinct from all other variables.
StepHypRef Expression
1 df-ga 18896 . . 3 GrpAct = (𝑔 ∈ Grp, 𝑠 ∈ V ↦ (Base‘𝑔) / 𝑏{𝑚 ∈ (𝑠m (𝑏 × 𝑠)) ∣ ∀𝑥𝑠 (((0g𝑔)𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑏𝑧𝑏 ((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))})
21elmpocl 7511 . 2 ( ∈ (𝐺 GrpAct 𝑌) → (𝐺 ∈ Grp ∧ 𝑌 ∈ V))
3 fvexd 6789 . . . . . . 7 ((𝑔 = 𝐺𝑠 = 𝑌) → (Base‘𝑔) ∈ V)
4 simplr 766 . . . . . . . . 9 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → 𝑠 = 𝑌)
5 id 22 . . . . . . . . . . 11 (𝑏 = (Base‘𝑔) → 𝑏 = (Base‘𝑔))
6 simpl 483 . . . . . . . . . . . . 13 ((𝑔 = 𝐺𝑠 = 𝑌) → 𝑔 = 𝐺)
76fveq2d 6778 . . . . . . . . . . . 12 ((𝑔 = 𝐺𝑠 = 𝑌) → (Base‘𝑔) = (Base‘𝐺))
8 isga.1 . . . . . . . . . . . 12 𝑋 = (Base‘𝐺)
97, 8eqtr4di 2796 . . . . . . . . . . 11 ((𝑔 = 𝐺𝑠 = 𝑌) → (Base‘𝑔) = 𝑋)
105, 9sylan9eqr 2800 . . . . . . . . . 10 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → 𝑏 = 𝑋)
1110, 4xpeq12d 5620 . . . . . . . . 9 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (𝑏 × 𝑠) = (𝑋 × 𝑌))
124, 11oveq12d 7293 . . . . . . . 8 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (𝑠m (𝑏 × 𝑠)) = (𝑌m (𝑋 × 𝑌)))
13 simpll 764 . . . . . . . . . . . . . 14 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → 𝑔 = 𝐺)
1413fveq2d 6778 . . . . . . . . . . . . 13 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (0g𝑔) = (0g𝐺))
15 isga.3 . . . . . . . . . . . . 13 0 = (0g𝐺)
1614, 15eqtr4di 2796 . . . . . . . . . . . 12 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (0g𝑔) = 0 )
1716oveq1d 7290 . . . . . . . . . . 11 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → ((0g𝑔)𝑚𝑥) = ( 0 𝑚𝑥))
1817eqeq1d 2740 . . . . . . . . . 10 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (((0g𝑔)𝑚𝑥) = 𝑥 ↔ ( 0 𝑚𝑥) = 𝑥))
1913fveq2d 6778 . . . . . . . . . . . . . . . 16 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (+g𝑔) = (+g𝐺))
20 isga.2 . . . . . . . . . . . . . . . 16 + = (+g𝐺)
2119, 20eqtr4di 2796 . . . . . . . . . . . . . . 15 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (+g𝑔) = + )
2221oveqd 7292 . . . . . . . . . . . . . 14 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (𝑦(+g𝑔)𝑧) = (𝑦 + 𝑧))
2322oveq1d 7290 . . . . . . . . . . . . 13 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → ((𝑦(+g𝑔)𝑧)𝑚𝑥) = ((𝑦 + 𝑧)𝑚𝑥))
2423eqeq1d 2740 . . . . . . . . . . . 12 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)) ↔ ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥))))
2510, 24raleqbidv 3336 . . . . . . . . . . 11 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (∀𝑧𝑏 ((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)) ↔ ∀𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥))))
2610, 25raleqbidv 3336 . . . . . . . . . 10 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (∀𝑦𝑏𝑧𝑏 ((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)) ↔ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥))))
2718, 26anbi12d 631 . . . . . . . . 9 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → ((((0g𝑔)𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑏𝑧𝑏 ((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥))) ↔ (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))))
284, 27raleqbidv 3336 . . . . . . . 8 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → (∀𝑥𝑠 (((0g𝑔)𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑏𝑧𝑏 ((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥))) ↔ ∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))))
2912, 28rabeqbidv 3420 . . . . . . 7 (((𝑔 = 𝐺𝑠 = 𝑌) ∧ 𝑏 = (Base‘𝑔)) → {𝑚 ∈ (𝑠m (𝑏 × 𝑠)) ∣ ∀𝑥𝑠 (((0g𝑔)𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑏𝑧𝑏 ((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))} = {𝑚 ∈ (𝑌m (𝑋 × 𝑌)) ∣ ∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))})
303, 29csbied 3870 . . . . . 6 ((𝑔 = 𝐺𝑠 = 𝑌) → (Base‘𝑔) / 𝑏{𝑚 ∈ (𝑠m (𝑏 × 𝑠)) ∣ ∀𝑥𝑠 (((0g𝑔)𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑏𝑧𝑏 ((𝑦(+g𝑔)𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))} = {𝑚 ∈ (𝑌m (𝑋 × 𝑌)) ∣ ∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))})
31 ovex 7308 . . . . . . 7 (𝑌m (𝑋 × 𝑌)) ∈ V
3231rabex 5256 . . . . . 6 {𝑚 ∈ (𝑌m (𝑋 × 𝑌)) ∣ ∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))} ∈ V
3330, 1, 32ovmpoa 7428 . . . . 5 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → (𝐺 GrpAct 𝑌) = {𝑚 ∈ (𝑌m (𝑋 × 𝑌)) ∣ ∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))})
3433eleq2d 2824 . . . 4 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → ( ∈ (𝐺 GrpAct 𝑌) ↔ ∈ {𝑚 ∈ (𝑌m (𝑋 × 𝑌)) ∣ ∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))}))
35 oveq 7281 . . . . . . . 8 (𝑚 = → ( 0 𝑚𝑥) = ( 0 𝑥))
3635eqeq1d 2740 . . . . . . 7 (𝑚 = → (( 0 𝑚𝑥) = 𝑥 ↔ ( 0 𝑥) = 𝑥))
37 oveq 7281 . . . . . . . . 9 (𝑚 = → ((𝑦 + 𝑧)𝑚𝑥) = ((𝑦 + 𝑧) 𝑥))
38 oveq 7281 . . . . . . . . . 10 (𝑚 = → (𝑦𝑚(𝑧𝑚𝑥)) = (𝑦 (𝑧𝑚𝑥)))
39 oveq 7281 . . . . . . . . . . 11 (𝑚 = → (𝑧𝑚𝑥) = (𝑧 𝑥))
4039oveq2d 7291 . . . . . . . . . 10 (𝑚 = → (𝑦 (𝑧𝑚𝑥)) = (𝑦 (𝑧 𝑥)))
4138, 40eqtrd 2778 . . . . . . . . 9 (𝑚 = → (𝑦𝑚(𝑧𝑚𝑥)) = (𝑦 (𝑧 𝑥)))
4237, 41eqeq12d 2754 . . . . . . . 8 (𝑚 = → (((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)) ↔ ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥))))
43422ralbidv 3129 . . . . . . 7 (𝑚 = → (∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)) ↔ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥))))
4436, 43anbi12d 631 . . . . . 6 (𝑚 = → ((( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥))) ↔ (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥)))))
4544ralbidv 3112 . . . . 5 (𝑚 = → (∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥))) ↔ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥)))))
4645elrab 3624 . . . 4 ( ∈ {𝑚 ∈ (𝑌m (𝑋 × 𝑌)) ∣ ∀𝑥𝑌 (( 0 𝑚𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧)𝑚𝑥) = (𝑦𝑚(𝑧𝑚𝑥)))} ↔ ( ∈ (𝑌m (𝑋 × 𝑌)) ∧ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥)))))
4734, 46bitrdi 287 . . 3 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → ( ∈ (𝐺 GrpAct 𝑌) ↔ ( ∈ (𝑌m (𝑋 × 𝑌)) ∧ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥))))))
48 simpr 485 . . . . 5 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → 𝑌 ∈ V)
498fvexi 6788 . . . . . 6 𝑋 ∈ V
50 xpexg 7600 . . . . . 6 ((𝑋 ∈ V ∧ 𝑌 ∈ V) → (𝑋 × 𝑌) ∈ V)
5149, 48, 50sylancr 587 . . . . 5 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → (𝑋 × 𝑌) ∈ V)
5248, 51elmapd 8629 . . . 4 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → ( ∈ (𝑌m (𝑋 × 𝑌)) ↔ :(𝑋 × 𝑌)⟶𝑌))
5352anbi1d 630 . . 3 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → (( ∈ (𝑌m (𝑋 × 𝑌)) ∧ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥)))) ↔ ( :(𝑋 × 𝑌)⟶𝑌 ∧ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥))))))
5447, 53bitrd 278 . 2 ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) → ( ∈ (𝐺 GrpAct 𝑌) ↔ ( :(𝑋 × 𝑌)⟶𝑌 ∧ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥))))))
552, 54biadanii 819 1 ( ∈ (𝐺 GrpAct 𝑌) ↔ ((𝐺 ∈ Grp ∧ 𝑌 ∈ V) ∧ ( :(𝑋 × 𝑌)⟶𝑌 ∧ ∀𝑥𝑌 (( 0 𝑥) = 𝑥 ∧ ∀𝑦𝑋𝑧𝑋 ((𝑦 + 𝑧) 𝑥) = (𝑦 (𝑧 𝑥))))))
Colors of variables: wff setvar class
Syntax hints:  wb 205  wa 396   = wceq 1539  wcel 2106  wral 3064  {crab 3068  Vcvv 3432  csb 3832   × cxp 5587  wf 6429  cfv 6433  (class class class)co 7275  m cmap 8615  Basecbs 16912  +gcplusg 16962  0gc0g 17150  Grpcgrp 18577   GrpAct cga 18895
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1913  ax-6 1971  ax-7 2011  ax-8 2108  ax-9 2116  ax-10 2137  ax-11 2154  ax-12 2171  ax-ext 2709  ax-sep 5223  ax-nul 5230  ax-pow 5288  ax-pr 5352  ax-un 7588
This theorem depends on definitions:  df-bi 206  df-an 397  df-or 845  df-3an 1088  df-tru 1542  df-fal 1552  df-ex 1783  df-nf 1787  df-sb 2068  df-mo 2540  df-eu 2569  df-clab 2716  df-cleq 2730  df-clel 2816  df-nfc 2889  df-ral 3069  df-rex 3070  df-rab 3073  df-v 3434  df-sbc 3717  df-csb 3833  df-dif 3890  df-un 3892  df-in 3894  df-ss 3904  df-nul 4257  df-if 4460  df-pw 4535  df-sn 4562  df-pr 4564  df-op 4568  df-uni 4840  df-br 5075  df-opab 5137  df-id 5489  df-xp 5595  df-rel 5596  df-cnv 5597  df-co 5598  df-dm 5599  df-rn 5600  df-iota 6391  df-fun 6435  df-fn 6436  df-f 6437  df-fv 6441  df-ov 7278  df-oprab 7279  df-mpo 7280  df-map 8617  df-ga 18896
This theorem is referenced by:  gagrp  18898  gaset  18899  gagrpid  18900  gaf  18901  gaass  18903  ga0  18904  gaid  18905  subgga  18906  gass  18907  gasubg  18908  lactghmga  19013  sylow1lem2  19204  sylow2blem2  19226  sylow3lem1  19232
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