The boundary–boundary correlation in an arbitrary oblique direction for the two-dimensional Ising model is calculated exactly using the topological interaction method. It is shown that these correlation functions satisfy Morita's sum rule not only for TTc but also for T⩽Tc. The asymptotic...

Finite-size scaling of energies in several isotropic XY chains with defects is discussed. The finite-size corrections of ground-state and low-lying energies in the models are calculated analytically and numerically. Critical exponents of some correlation functions of the relevant models are also...