Reidemeister spectra for almost-crystallographic groups KU Leuven
The notion of conjugacy in a group can be generalised to twisted conjugacy. For any endomorphism φ of a group G, we may define an equivalence relation ~ on G by ∀g,g' ∈ G: g ~ g' if and only if ∃h ∈ G: g = hg'φ(h)⁻¹. The number of equivalence classes is called the Reidemeister number ...