We continue our study from Peterzil et al. (2022, Preprint, arXiv:2208.08293) of finite-dimensional definable groups in models of the theory
$T_{\partial }$
, the model companion of an o-minimal
${\mathcal {L}}$
-theory T expanded by a generic derivation
$\partial $
as in Fornasiero and Kaplan (2021, Journal of Mathematical Logic 21, 2150007).
We generalize Buium’s notion of an algebraic D-group to
${\mathcal {L}}$
-definable D-groups, namely
$(G,s)$
, where G is an
${\mathcal {L}}$
-definable group in a model of T, and
$s:G\to \tau (G)$
is an
${\mathcal {L}}$
-definable group section. Our main theorem says that every definable group of finite dimension in a model of
$T_\partial $
is definably isomorphic to a group of the form
$$ \begin{align*}(G,s)^\partial=\{g\in G:s(g)=\nabla g\},\end{align*} $$
for some
${\mathcal {L}}$
-definable D-group
$(G,s)$
(where
$\nabla (g)=(g,\partial g)$
).
We obtain analogous results when T is either the theory of p-adically closed fields or the theory of pseudo-finite fields of characteristic
$0$
.