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Free amalgamation and automorphism groups (1406.1130v1)
Published 4 Jun 2014 in math.LO
Abstract: Let L be a countable elementary language, N be a Fraisse limit. We consider free amalgamation for L-structures where L is arbitrary. If free amalgamation for finitely generated substructures exits in N, then it is a stationary independece relation in the sense of K.Tent and M.Ziegler [TZ12b]. Therefore Aut(N) is universal for Aut(M) for all substructures M of N. This follows by a result of I.M\"uller [Mue13] We show that c-nilpotent graded Lie algebras over a finite field and c-nilpotent groups of exponent p (c < p) with extra predicates for a central Lazard series provide examples. We replace the proof in [Bau04] of the amalgamation of c-nilpotent graded Lie algebras over a field by a correct one.