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Abstract
In this paper we study the structure of random van Kampen diagrams over finitely presented groups. Such diagrams have many remarkable properties. In particular, we show that a random van Kampen diagram over a given group is hyperbolic, even though the group itself may not be hyperbolic. This allows one to design new fast algorithms for the Word Problem in groups. We introduce and study a new filling function, the depth of van Kampen diagrams, – a crucial algorithmic characteristic of null-homotopic words in the group.
Keywords.: Word problem; finitely presented groups; search algorithms; van Kampen diagram; hyperbolic diagrams; Todd–Coxeter algorithm
Received: 2011-01-20
Published Online: 2011-05-27
Published in Print: 2011-May
© de Gruyter 2011
