Source: J. Symbolic Logic Volume 75, Issue 1
(2010), 372-386.
Let G be a group definable in a monster model 𝔠 of a rosy theory
satisfying NIP. Assume that G has hereditarily finitely satisfiable
generics and 1 < Uþ(G) < ∞. We prove that if G acts definably
on a definable set of Uþ-rank 1, then, under some general assumption
about this action, there is an infinite field interpretable in 𝔠.
We conclude that if G is not solvable-by-finite and it acts faithfully
and definably on a definable set of Uþ-rank 1,
then there is an infinite field interpretable in 𝔠.
As an immediate consequence, we get that if G has a definable subgroup H
such that Uþ(G)=Uþ(H)+1 and G/⋂g ∈ GHg is not
solvable-by-finite, then an infinite field interpretable in 𝔠 also exists.
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