On bounded languages and the geometry of nilpotent groups
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Combinatorial and Geometric Group Theory, Edinburgh 1993, London 
Math. Soc. Lecture Notes <b> 204</b>, Cambr. U. P. 1995, 1-15 (with 
Martin Bridson.


Bounded languages are a class of formal languages which includes all
context free languages of polynomial growth. We prove that if a finitely
generated group G admits a combing by a bounded language and this combing
satisfies the asynchronous fellow traveller property, then either G is
virtually abelian, or else G contains an element g of infinite order such
that g^n and g^m are conjugate for some 0<n<m.