It is shown that two different
topologies on a group G both of which make it into a locally compact group, usually
give rise to different continuous irreducible unitary representations. To be more
precise: If the continuous irreducible unitary representations of G coincide for the two
topologies, then these topologies are the same in the following cases: The topologies
are comparable; There exists a normal subgroup of G, open and σ-compact in one of
the topologies.