PP200204: Lee, Troy (2002) Arithmetical Definability over Finite Structures. [Report]
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Abstract
Arithmetical definability has been extensively studied over the
natural numbers. In this paper, we take up the study of arithmetical
definability over finite structures, motivated by the correspondence
between uniform $\AC^0$ and $\FO(\PLUS,\TIMES)$. We prove finite
analogs of three classic results in arithmetical definability, namely
that $<$ and TIMES can firstorder define PLUS, that $<$ and DIVIDES
can firstorder define TIMES, and that $<$ and COPRIME can firstorder
define TIMES.
The first result sharpens the known equivalence
${\FO(\PLUS,\TIMES)=}{\FO(\BIT)}$ to $\FO(<,\TIMES)=\FO(\BIT)$,
answering a question raised by Barrington et al. (LICS 2001) about the
Crane Beach Conjecture. Together with previous results on the Crane
Beach Conjecture, our results imply that $\FO(\PLUS)$ is strictly less
expressive than $\FO(<,\TIMES)=\FO(<,\DIVIDES)=\FO(<,\COPRIME)$. In
more colorful language, one could say this containment adds evidence
to the belief that multiplication is harder than addition.
Item Type:  Report 

Report Nr:  PP200204 
Series Name:  Prepublication (PP) Series 
Year:  2002 
Uncontrolled Keywords:  Arithmetical Definability; Descriptive Complexity; Finite Model Theory 
Date Deposited:  12 Oct 2016 14:36 
Last Modified:  12 Oct 2016 14:36 
URI:  https://eprints.illc.uva.nl/id/eprint/68 
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