Abstract:
A long-standing conjecture of Nicolas Bergeron and Akshay Venkatesh
predicts that in closed hyperbolic 3-manifolds, the amount of torsion in
the first homology of finite-sheeted normal covers should grow
exponentially with the degree of the cover as the covers become larger,
at a rate reflecting the volume of the manifold. Yet no finitely
presented residually finite group is known to exhibit exponential
torsion growth in first homology along an exhausting chain of
finite-index normal subgroups.
In this talk I will explain how a two-dimensional lens offers a clearer
view of some of the underlying mechanisms that create homological
torsion in finite covers, and why obtaining exponential growth may be
more tractable in this setting. I will also discuss how these ideas
connect to the question of profinite rigidity: how much information
about a group is encoded in its finite quotients.