Statistical Physics Group

Off-diagonal profiles Ï+od(Ï...) of local densities (e.g. order parameter or energy density) are calculated at the bulk critical point, by conformal methods, on a strip with transverse coordinate Ï..., for different types of boundary conditions (free, fixed and mixed). Such profiles, which are defined by the non-vanishing matrix element ãEUR^0|Ï+Ì`(Ï...)|Ï+ãEURo/oo of the appropriate operator Ï+Ì`(Ï...) between the ground state and the corresponding lowest excited state of the strip Hamiltonian, enter into the expression of two-point correlation functions on a strip. They are of interest in the finite-size scaling study of bulk and surface critical behaviour since they allow the elimination of regular contributions. The conformal profiles, which are obtained through a conformal transformation of the correlation functions from the half-plane to the strip, are in agreement with the results of a direct calculation, for the energy density of the two-dimensional Ising model.