Droplet Excitations for the Spin-1/2 XXZ Chain with Kink Boundary   Conditions
  We give a precise definition for excitations consisting of a droplet of size n in the XXZ chain with various choices of boundary conditions, including kink boundary conditions and prove that, for each n, the droplet energies converge to a boundary condition independent value in the thermodynamic limit. We rigorously compute an explicit formula for this limiting value using the Bethe ansatz. 
Bruno Nachtergaele, Wolfgang Spitzer, Shannon Starr