Exact partition function and boundary state of 2D massive Ising field theory with boundary magnetic field Original Research Article

We compute the exact partition function, the universal ground-state degeneracy and boundary state of the 2D Ising model with boundary magnetic field at off-critical temperatures. The model has a domain that exhibits states localized near the boundaries. We study this domain of boundary bound state and derive exact expressions for the “g function” and boundary state for all temperatures and boundary magnetic fields. In the massless limit we recover the boundary renormalization group flow between the conformally invariant free and fixed boundary conditions.