  Given a Lagrangian submanifold $L$ in a symplectic manifold $X$, the
homological Lagrangian monodromy group $\mathcal{H}_L$ describes how
Hamiltonian diffeomorphisms of $X$ preserving $L$ setwise act on $H_*(L)$. We
begin a systematic study of this group when $L$ is a monotone Lagrangian
$n$-torus. Among other things, we describe $\mathcal{H}_L$ completely when $L$
is a monotone toric fibre, make significant progress towards classifying the
groups than can occur for $n=2$, and make a conjecture for general $n$. Our
classification results rely crucially on arithmetic properties of Floer
cohomology rings.

Symplectic Geometry