Abstract A finitely generated group

We exploit Zlil Sela’s description of the structure of groups having the same elementary theory as free groups: they and their finitely generated subgroups form a prescribed subclass E of the hyperbolic limit groups. We prove that if G1, . . . , Gn are in E then a subgroup Γ ⊂ G1 × · · · × Gn is of type FPn if and only if Γ is itself, up to finite index, the direct product of at most n groups f...

Let G1 × G2 be a subgroup of SO3(R) such that the two factors G1 and G2 are non-trivial groups. We show that if G1 × G2 is not abelian, then one factor is the (abelian) group of order 2, and the other factor is nonabelian and contains an element of order 2. There exist finite and infinite such non-abelian subgroups. Let F2 be the free group of rank 2. It is well-known that the group SO3(R) has ...