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COMPUTING STRENGTH OF STRUCTURES RELATED TO THE FIELD OF REAL NUMBERS
Published online by Cambridge University Press: 21 March 2017
Abstract
In [8], the third author defined a reducibility
$\le _w^{\rm{*}}$
that lets us compare the computing power of structures of any
cardinality. In [6], the first two authors showed that the ordered field of
reals
${\cal R}$
lies strictly above certain related structures. In the present
paper, we show that
$\left( {{\cal R},exp} \right) \equiv _w^{\rm{*}}{\cal R}$
. More generally, for the weak-looking structure
${\cal R}$
ℚ consisting of the real numbers with
just the ordering and constants naming the rationals, all
o-minimal expansions of
${\cal R}$
ℚ are equivalent to
${\cal R}$
. Using this, we show that for any analytic function
f,
$\left( {{\cal R},f} \right) \equiv _w^{\rm{*}}{\cal R}$
. (This is so even if
$\left( {{\cal R},f} \right)$
is not o-minimal.)
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- Copyright © The Association for Symbolic Logic 2017
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