Conformal perturbation theory from open string field theory

Conformal boundary conditions in two-dimensional conformal field theories are still mostly an uncharted territory. Even less is known about the relevant boundary deformations that connect them. A natural approach to the problem is via conformal perturbation theory, which however becomes quickly intractable. Using the formalism of open string field theory, we construct the corresponding classical solution, from which we can easily extract the boundary theory data. As a simple illustration we calculate the boundary degeneracy $g$ to next-to-leading order for a generic theory.