Proof of a conjecture by Scott concerning energy levels in the quantum DST equation

Scott has recently studied the soliton binding energy in the quantum discrete self-trapping (DST) equation. His results depend on an eigenvalue of a certain matrix in the limit of large numbers of degrees of freedom, as conjectured on the basis of numerical calculations. We give a straightforward analytic proof that the conjecture is correct. The technique can be applied to other similar problems.