Source: Notre Dame J. Formal Logic Volume 49, Number 4
(2008), 345-360.
A model of Peano Arithmetic is short recursively saturated if it
realizes all its bounded finitely realized recursive types. Short
recursively saturated models of
$\PA$ are exactly the elementary
initial segments of recursively saturated models of
$\PA$. In this
paper, we survey and prove results on short recursively saturated
models of
$\PA$ and their automorphisms. In particular, we
investigate a certain subgroup of the automorphism group of such
models. This subgroup, denoted
$G|_{M(a)}$, contains all the
automorphisms of a countable short recursively saturated model of
which can be extended
to an automorphism of the countable recursively saturated elementary end extension of
the model.
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