Derek F. Holt, Sarah Rees, Claas E. Röver, Richard M. Thomas
We study the class of co-context-free groups. We define a co-context-free group to be one whose co-word problem (the complement of its word problem) is context-free. This class is larger than the...
Commensurations and Subgroups of Finite Index of Thompson's Group F (2007)
Burillo, José, Cleary, Sean, Röver, Claas E.
We determine the abstract commensurator com(F) of Thompson's group F and describe it in terms of piecewise linear homeomorphisms of the real line and in terms of tree pair diagrams. We show com (F)...
Groups with context-free co-word problem (2005)
Holt, Derek F., Rees, Sarah, Röver, Claas E., Thomas, Richard M.
The class of co-context-free groups is studied. A co-context-free group is defined as one whose coword problem (the complement of its word problem) is context-free. This class is larger than the...
Groups with a context-free co-word problem (2005)
Holt, D.F., Rees, Sarah, Röver, Claas E., Thomas, Richard M.
On real-time word problems (2003)
Holt, Derek F., Röver, Claas E.
It is proved that the word problem of the direct product of two free groups of rank 2 can be recognised by a 2-tape real-time but not by a 1-tape real-time Turing machine. It is also proved that the...