A tetrachotomy for expansions of the real ordered additive group · arXivDesk
1709.03150Sep 10, 2017A previous version of this paper was disseminated under the title "On continuous functions definable in expansions of the ordered real additive group''
A tetrachotomy for expansions of the real ordered additive group
Let R be an expansion of the ordered real additive group. When R is o-minimal, it is known that either R defines an ordered field isomorphic to (R,<,+,⋅) on some open subinterval I⊆R
Nearby in the stack
, or
R
is a reduct of an ordered vector space. We say
R
is field-type if it satisfies the former condition. In this paper, we prove a more general result for arbitrary expansions of
(R,<,+)
. In particular, we show that for expansions that do not define dense
ω
-orders (we call these type A expansions), an appropriate version of Zilber's principle holds. Among other things we conclude that in a type A expansion that is not field-type, every continuous definable function