2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/17940Using conformal invariance, we show that the non-universal exponent eta_0 associated with the decay of correlations along a defect line of modified bonds in the square-lattice Ising model is related to the amplitude A_0=xi_n/n of the correlation length ξ_n(K_c) at the bulk critical coupling K_c, on a strip with width n, periodic boundary conditions and two equidistant defect lines along the strip, through A_0=(πη_0)^{-1}.Old paper, for archiving. 5 pages, 4 figures, IOP macro, epsfStatistical Mechanicstext