Theorem ackm 4792

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 4791. 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 4791	. 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 4758	. 2 |- E.f(f (_ x /\ f Fn dom x)
3	1, 2	mpgbi 989	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 956   = wceq 958   e. wcel 960  E.wex 982   (_ wss 2050  dom cdm 3176   Fn wfn 3183

This theorem was proved from axioms:  ax-1 4  ax-2 5  ax-3 6  ax-mp 7  ax-7 964  ax-gen 965  ax-8 966  ax-9 967  ax-10 968  ax-11 969  ax-12 970  ax-13 971  ax-14 972  ax-17 973  ax-4 975  ax-5o 977  ax-6o 980  ax-9o 1125  ax-10o 1142  ax-16 1212  ax-11o 1220  ax-ext 1462  ax-rep 2698  ax-sep 2708  ax-nul 2715  ax-pow 2748  ax-pr 2785  ax-un 2872  ax-ac 4754

This theorem depends on definitions:  df-bi 147  df-or 224  df-an 225  df-ex 983  df-sb 1174  df-eu 1384  df-mo 1385  df-clab 1467  df-cleq 1472  df-clel 1475  df-ne 1590  df-ral 1652  df-rex 1653  df-reu 1654  df-rab 1655  df-v 1815  df-dif 2052  df-un 2053  df-in 2054  df-ss 2056  df-nul 2284  df-pw 2406  df-sn 2416  df-pr 2417  df-op 2420  df-uni 2508  df-iun 2572  df-br 2625  df-opab 2672  df-id 2841  df-xp 3190  df-rel 3191  df-cnv 3192  df-co 3193  df-dm 3194  df-rn 3195  df-res 3196  df-ima 3197  df-fun 3198  df-fn 3199  df-fv 3204

Copyright terms: Public domain