Conformal Manifolds with Boundaries or Defects

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.