  We analyze the defect scaling Lee-Yang model from the perturbed defect
conformal field theory (DCFT) point of view. First the defect Lee-Yang model is
solved by calculating its structure constants from the sewing relations.
Integrable defect perturbations are identified in conformal defect perturbation
theory. Then pure defect flows connecting integrable conformal defects are
described. We develop a defect truncated conformal space approach (DTCSA) to
analyze the one parameter family of integrable massive perturbations in finite
volume numerically. Fusing the integrable defect to an integrable boundary the
relation between the IR and UV parameters can be derived from the boundary
relations. We checked these results by comparing the spectrum for large volumes
to the scattering theory.

High Energy Physics - Theory