Date of Original Version
We show that for conformally invariant two-dimensional systems, the amplitude of the finite-size corrections to the free energy of an infinitely long strip of width L at criticality is linearly related to the conformal anomaly number c, for various boundary conditions. The result is confirmed by renormalization-group arguments and numerical calculations. It is also related to the magnitude of the Casimir effect in an interacting one-dimensional field theory, and to the low-temperature specific heat in quantum chains.
H. W. J. Blöte, John L. Cardy, and M. P. Nightingale. (1986). "Conformal invariance, the central charge, and universal finite-size amplitudes at criticality." Physical Review Letters, 56(7), 742. Available at: http://dx.doi.org/10.1103/PhysRevLett.56.742