Finite index subgroups without unique product in graphical small cancellation groups: Figure 1.
Finite index subgroups without unique product in graphical small cancellation groups: Figure 1.
For every integer k ⩾ 1 , we construct a torsion-free hyperbolic group without unique product all of whose subgroups up to index k are themselves non-unique product groups. This is achieved by generalizing a construction of Comerford to graphical small cancellation presentations, showing that for every subgroup H of …