[FOM] 509: More Undefinable Elements
Harvey Friedman
hmflogic at gmail.com
Tue Nov 27 22:03:35 EST 2012
THIS RESEARCH WAS PARTIALLY SUPPORTED BY THE JOHN TEMPLETON FOUNDATION
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THIS POSTING IS A CONTINUATION OF
http://www.cs.nyu.edu/pipermail/fom/2012-November/016806.html
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The paper at http://www.math.osu.edu/~friedman.8/manuscripts.html #74,
proves "there is a structure in a finite relational type with a unique
undefinable element."
Consider this:
There is a structure in a finite relational type with exactly n
undefinable elements.
If n > 1 then the above is trivial. Take n distinct elements with no
constant, relation, or function symbols. Of course, = is always
allowed.
However, consider these sharper forms.
There is a structure in a finite relational type with exactly n
undefinable elements, each of which is definable from any of the
others.
There is a structure in a finite relational type with exactly n
undefinable elements, none of which is definable from the remaining
n-1.
The first of these is very easy to prove, for any n >= 1. Take
0,1,...,n-1, with the function f(x) = x+1 mod n.
The second of these can be proved, for any n >= 1, by adapting the
proof in http://www.math.osu.edu/~friedman.8/manuscripts.html #74,
As in the paper, one can take the structure to be a graph, and one can
use "there are infinitely many" and other quantitative quantifiers.
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I use http://www.math.ohio-state.edu/~friedman/ for downloadable
manuscripts. This is the 509th in a series of self contained numbered
postings to FOM covering a wide range of topics in f.o.m. The list of
previous numbered postings #1-449 can be found
in the FOM archives at
http://www.cs.nyu.edu/pipermail/fom/2010-December/015186.html
450: Maximal Sets and Large Cardinals II 12/6/10 12:48PM
451: Rational Graphs and Large Cardinals I 12/18/10 10:56PM
452: Rational Graphs and Large Cardinals II 1/9/11 1:36AM
453: Rational Graphs and Large Cardinals III 1/20/11 2:33AM
454: Three Milestones in Incompleteness 2/7/11 12:05AM
455: The Quantifier "most" 2/22/11 4:47PM
456: The Quantifiers "majority/minority" 2/23/11 9:51AM
457: Maximal Cliques and Large Cardinals 5/3/11 3:40AM
458: Sequential Constructions for Large Cardinals 5/5/11 10:37AM
459: Greedy CLique Constructions in the Integers 5/8/11 1:18PM
460: Greedy Clique Constructions Simplified 5/8/11 7:39PM
461: Reflections on Vienna Meeting 5/12/11 10:41AM
462: Improvements/Pi01 Independence 5/14/11 11:53AM
463: Pi01 independence/comprehensive 5/21/11 11:31PM
464: Order Invariant Split Theorem 5/30/11 11:43AM
465: Patterns in Order Invariant Graphs 6/4/11 5:51PM
466: RETURN TO 463/Dominators 6/13/11 12:15AM
467: Comment on Minimal Dominators 6/14/11 11:58AM
468: Maximal Cliques/Incompleteness 7/26/11 4:11PM
469: Invariant Maximality/Incompleteness 11/13/11 11:47AM
470: Invariant Maximal Square Theorem 11/17/11 6:58PM
471: Shift Invariant Maximal Squares/Incompleteness 11/23/11 11:37PM
472. Shift Invariant Maximal Squares/Incompleteness 11/29/11 9:15PM
473: Invariant Maximal Powers/Incompleteness 1 12/7/11 5:13AMs
474: Invariant Maximal Squares 01/12/12 9:46AM
475: Invariant Functions and Incompleteness 1/16/12 5:57PM
476: Maximality, CHoice, and Incompleteness 1/23/12 11:52AM
477: TYPO 1/23/12 4:36PM
478: Maximality, Choice, and Incompleteness 2/2/12 5:45AM
479: Explicitly Pi01 Incompleteness 2/12/12 9:16AM
480: Order Equivalence and Incompleteness
481: Complementation and Incompleteness 2/15/12 8:40AM
482: Maximality, Choice, and Incompleteness 2 2/19/12 7:43AM
483: Invariance in Q[0,n]^k 2/19/12 7:34AM
484: Finite Choice and Incompleteness 2/20/12 6:37AM__
485: Large Large Cardinals 2/26/12 5:55AM
486: Naturalness Issues 3/14/12 2:07PM
487: Invariant Maximality/Naturalness 3/21/12 1:43AM
488: Invariant Maximality Program 3/24/12 12:28AM
489: Invariant Maximality Programs 3/24/12 2:31PM
490: Invariant Maximality Program 2 3/24/12 3:19PM
491: Formal Simplicity 3/25/12 11:50PM
492: Invariant Maximality/conjectures 3/31/12 7:31PM
493: Invariant Maximality/conjectures 2 3/31/12 7:32PM
494: Inv Max Templates/Z+up, upper Z+ equiv 4/5/12 4:17PM
495: Invariant Finite Choice 4/5/12 4:18PM
496: Invariant Finite Choice/restatement 4/8/12 2:18AM
497: Invariant Maximality Restated 5/2/12 2:49AM
498: Embedded Maximal Cliques 1 9/18/12 12:43AM
499. Embedded Maximal Cliques 2 9/19/12 2:50AM
500: Embedded Maximal Cliques 3 9/20/12 10:15PM
501: Embedded Maximal Cliques 4 9/23/12 2:16AM
502: Embedded Maximal Cliques 5 9/26/12 1:21AM
503: Proper Classes of Graphs 10/13/12 12:17PM
504. Embedded Maximal Cliques 6 10/14/12 12:49PM
505: Function Transfer Theory 10/21/12 2:15AM
506: Finite Embedded Weakly Maximal Cliques 10/23/12 12:53AM
507: Finite Embedded Dominators 11/6/12 6:40AM
508: Unique Undefinable Elements 11/27/12 3:30PM
Harvey Friedman
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