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.