Recall that two finitely presented groups
and
are “proper
–equivalent” if they can be
realized by finite
–dimensional
CW–complexes whose universal covers are proper
–equivalent
as (strongly) locally finite CW–complexes. This purely topological relation is
coarser than the quasi-isometry relation, and those groups which are
–ended
and semistable at infinity are classified, up to proper
–equivalence,
by their fundamental pro-group. We show that if
and
are proper
–equivalent
and semistable at each end, then any two finite graph of groups decompositions of
and
with finite edge
groups and finitely presented vertex groups with at most one end must have the same set of proper
–equivalence
classes of (infinite) nonsimply connected at infinity vertex groups
(without multiplicities). Moreover, those simply connected at infinity
vertex groups in such a decomposition (if any) are all proper
–equivalent
to
.
Thus, under the semistability hypothesis, this answers a question concerning
the classification of infinite ended finitely presented groups up to proper
–equivalence, and shows again the
behavior of proper
–equivalences
versus quasi-isometries, in which the geometry of the group is taken into
account.
Keywords
proper homotopy, proper $2$–equivalence, quasi-isometry,
finitely presented group