We solve the one-dimensional massive Thirring model, which is equivalent to the one-dimensional sine-Gordon model, with two types of Dirchlet boundary conditions: open boundary conditions (OBC) and twisted open boundary conditions (OBC). The system exhibits a duality symmetry which relates models with opposite bare mass parameters and boundary conditions, i. e: m₀ - m₀, OBC. For m₀0 and OBC, the trivial phase occurs, whereas the topological phase occurs for m₀>0 and OBC. In addition, we analyze the structure of the boundary excitations, finding significant differences between the attractive (g>0) and the repulsive (g<0) regimes.
Pasnoori et al. (Tue,) studied this question.