Often one can only view groups through their finite quotations. This
naturally leads to the notion of a profinite completion of a group
which combines all finite quotients.
One can ask which group properties are profinite properties, ie. can
be determined only looking at the profinite completion and not from
the group itself. Some properties (like being abelain) are clearly
profinite but for others the question is quite subtle. In this talk I
will answer a question by M. Bridson if being torsion is a profinite
property -- essentially this boils town to constricting two groups G
and G' which have the same profinite completion, where G is torsion
and G' is not.