Automorphisms groups of countable recursively saturated models

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Generic automorphisms and the small index property

Lascar showed that countable arithmetically saturated models of $PA$ have generic automorphisms and used them to show that automorphism groups of these models have the small index property. Lascar, Daniel, The small index property and recursively saturated models of Peano arithmetic. Automorphisms of first-order structures, 281–292, Oxford Sci. Publ., Oxford Univ. Press, New York, 1994.

Do automorphism groups of countable recursively saturated, but nor arithmetically saturated models of $PA$ have generic automorphisms? Do they have the small index property.


It is shown in Kossak, Roman; Kotlarski, Henryk; Schmerl, James H. On maximal subgroups of the automorphism group of a countable recursively saturated model of PA. Ann. Pure Appl. Logic 65 (1993), no. 2, 125–148. that every open subgroup of the automorphism group of a countable recursively saturated model of $PA$ extends to a maximal subgroup. Is the same true for countable models which are recursively saturated, but not arithmetically saturated?