Eine Bemerkung zu den Nielsen-Transformationen.
Eine rekursiv präsentierte Gruppe mit unentscheidbarem Wortlaut.
Equivalence élémentaire entre groupes finis-par-abéliens de type fini.
Every braid admits a short sigma-definite expression
A result by Dehornoy (1992) says that every nontrivial braid admits a -definite expression, defined as a braid word in which the generator with maximal index appears with exponents that are all positive, or all negative. This is the ground result for ordering braids. In this paper, we enhance this result and prove that every braid admits a -definite word expression that, in addition, is quasi-geodesic. This establishes a longstanding conjecture. Our proof uses the dual braid monoid and a new...
Existentially closed -groups
Existentially Closed Locally Finite Central Extensions: Multipliers and Local Systems.
Experimenting with infinite groups. I.