  Gapped phases with long-range entanglement may admit gapped boundaries. If
the boundary is gapped, the ground-state degeneracy is well-defined and can be
computed using methods of Topological Quantum Field Theory. We derive a general
formula for the ground-state degeneracy for abelian Fractional Quantum Hall
phases, including the cases when connected components of the boundary are
subdivided into an arbitrary number of segments, with a different boundary
condition on each segment, and in the presence of an arbitrary number of
boundary domain walls.
