Theorem ackm 4762

Description: A remarkable equivalent to the Axiom of Choice that has only 5 quantifiers (when expanded to e., = primitives in prenex form), discovered and proved by Kurt Maes. This establishes a new record, reducing from 6 to 5 the largest number of quantified variables needed by any ZFC axiom. The ZF-equivalence to AC is shown by theorem aceqkm 4761. Maes found this version of AC in April, 2004 (replacing a longer version, also with 5 quantifiers, that he found in November, 2003). See Kurt Maes, "A 5-quantifier (e.,=)-expression ZF-equivalent to the Axiom of Choice" (http://arxiv.org/PS_cache/arxiv/pdf/0705/0705.3162v1.pdf).

The original FOM posts are: http://www.cs.nyu.edu/pipermail/fom/2003-November/007631.html http://www.cs.nyu.edu/pipermail/fom/2003-November/007641.html.

Assertion

Ref	Expression
ackm	|- A.xE.yA.zE.vA.u((y e. x /\ (z e. y -> ((v e. x /\ -. y = v) /\ z e. v))) \/ (-. y e. x /\ (z e. x -> ((v e. z /\ v e. y) /\ ((u e. z /\ u e. y) -> u = v)))))

Distinct variable group:   x,y,z,v,u

Proof of Theorem ackm

Step	Hyp	Ref	Expression
1		aceqkm 4761	. 2 |- (A.xE.f(f (_ x /\ f Fn dom x) <-> A.xE.yA.zE.vA.u((y e. x /\ (z e. y -> ((v e. x /\ -. y = v) /\ z e. v))) \/ (-. y e. x /\ (z e. x -> ((v e. z /\ v e. y) /\ ((u e. z /\ u e. y) -> u = v))))))
2		ac7 4728	. 2 |- E.f(f (_ x /\ f Fn dom x)
3	1, 2	mpgbi 985	1 |- A.xE.yA.zE.vA.u((y e. x /\ (z e. y -> ((v e. x /\ -. y = v) /\ z e. v))) \/ (-. y e. x /\ (z e. x -> ((v e. z /\ v e. y) /\ ((u e. z /\ u e. y) -> u = v)))))

Syntax hints:  -. wn 2   -> wi 3   \/ wo 222   /\ wa 223  A.wal 952   = wceq 954   e. wcel 956  E.wex 978   (_ wss 2043  dom cdm 3165   Fn wfn 3172

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-7 960  ax-gen 961  ax-8 962  ax-9 963  ax-10 964  ax-11 965  ax-12 966  ax-13 967  ax-14 968  ax-17 969  ax-4 971  ax-5o 973  ax-6o 976  ax-9o 1121  ax-10o 1138  ax-16 1208  ax-11o 1216  ax-ext 1457  ax-rep 2688  ax-sep 2698  ax-nul 2705  ax-pow 2737  ax-pr 2774  ax-un 2861  ax-ac 4724

This theorem depends on definitions:  df-bi 147  df-or 224  df-an 225  df-ex 979  df-sb 1170  df-eu 1380  df-mo 1381  df-clab 1462  df-cleq 1467  df-clel 1470  df-ne 1584  df-ral 1646  df-rex 1647  df-reu 1648  df-rab 1649  df-v 1808  df-dif 2045  df-un 2046  df-in 2047  df-ss 2049  df-nul 2277  df-pw 2398  df-sn 2408  df-pr 2409  df-op 2412  df-uni 2499  df-iun 2563  df-br 2615  df-opab 2662  df-id 2830  df-xp 3179  df-rel 3180  df-cnv 3181  df-co 3182  df-dm 3183  df-rn 3184  df-res 3185  df-ima 3186  df-fun 3187  df-fn 3188  df-fv 3193

Copyright terms: Public domain