Complexity of Word Problems for HNN-Extensions

  title={Complexity of Word Problems for HNN-Extensions},
  author={Markus Lohrey},
The computational complexity of the word problem in HNNextension of groups is studied. HNN-extension is a fundamental construction in combinatorial group theory. It is shown that the word problem for an ascending HNN-extension of a group H is logspace reducible to the so-called compressed word problem for H . The main result of the paper states that the word problem for an HNN-extension of a hyperbolic group H with cyclic associated subgroups can be solved in polynomial time. This result can be… Expand

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