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Polynomial-time proofs that groups are hyperbolic. (English) Zbl 07312489
Summary: It is undecidable in general whether a given finitely presented group is word hyperbolic. We use the concept of pregroups, introduced by Stallings (1971), to define a new class of van Kampen diagrams, which represent groups as quotients of virtually free groups. We then present a polynomial-time procedure that analyses these diagrams, and either returns an explicit linear Dehn function for the presentation, or returns , together with its reasons for failure. Furthermore, if our procedure succeeds we are often able to produce in polynomial time a word problem solver for the presentation that runs in linear time. Our algorithms have been implemented, and when successful they are many orders of magnitude faster than KBMAG, the only comparable publicly available software.
##### MSC:
 20F Special aspects of infinite or finite groups 57M General low-dimensional topology 53C Global differential geometry
##### Keywords:
hyperbolic groups; word problem; van Kampen diagrams; curvature
##### Software:
AUTOMATA; GAP; kbmag; Magma
Full Text:
##### References:
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