Conformal invariance and linear defects in the two-dimensional Ising model

Using conformal invariance, the author shows that the nonuniversal 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/ 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 =( pi eta 0 ) -1 .