The XX-model with boundaries. Part II: Finite size scaling and partition functions

Abstract

We compute the continuum limit of the spectra for the XX-model with arbitrary complex boundary fields. In the case of hermitian boundary terms one obtains the partition functions of the free compactified boson field on a cylinder with Neumann-Neumann, Dirichlet-Neumann or Dirichlet-Dirichlet boundary conditions. This applies also for certain non-hermitian boundaries. For special cases we also compute the free surface energy. For certain non-hermitian boundary terms the results are more complex.Here one obtains logarithmic corrections to the free surface energy. The asymmetric version of the XX-model with boundaries (this includes the Dzyaloshinsky-Moriya interaction)is also discussed.