Conformal Manifolds with Boundaries or Defects

Abstract: We discuss conformal manifolds for conformal field theories with boundaries or defects. Using conformal perturbation theory we derive constraints on coefficients appearing in the boundary operator product expansion and three-point functions that need to be satisfied for the existence of marginal couplings. We present several explicit examples where we confirm that $\beta$-functions vanish using a position space regularization, differential regularization. Where possible, we confirm that our $\beta$-function results agree with the existing literature.