Strong coupling limit of Bethe ansatz solutions in massive Thirring model

We study the strong coupling limit of the Bethe ansatz solutions in the massive Thirring model. We find analytical expressions for the energy eigenvalues for the vacuum state as well as n particle-n hole states. This formula is compared with the numerical results and is found to achieve a very good agreement. Also, it is found that the two particle-two hole and higher particle-hole states describe n-free bosons states in this limit. The behaviors of the strong coupling limit of the boson mass for various model calculations are examined. We discuss an ambiguity of the coupling constant normalization due to the current regularization