Dehn Functions, the Word Problem, and the Bounded Word Problem For   Decidable Group Presentations
  We construct examples of finitely generated decidable group presentations that satisfy certain combinations of solvability for the word problem, solvability for the bounded word problem, and computablity for the Dehn function. We prove that no finitely generated decidable presentations exist satisfying the combinations for which we do not provide examples. The presentations we construct are also minimal. These constructions answer an open question asked by R.I. Grigorchuk and S.V. Ivanov. Our approach uses machinery developed by Birget, Ol'shanskii, Rips, and Sapir for constructing finite group presentations that simulate Turing machines. We generalize this machinery to construct finitely generated decidable group presentations that simulate computing objects similar to oracle Turing machines. 
Desmond Cummins
math.GR