BCFT and OSFT moduli: an exact perturbative comparison

Starting from the pseudo- B0B0 gauge solution for marginal deformations in OSFT, we analytically compute the relation between the perturbative deformation parameter λ~λ~ in the solution and the BCFT marginal parameter λλ , up to fifth order, by evaluating the Ellwood invariants. We observe that the microscopic reason why λ~λ~ and λλ are different is that the OSFT propagator renormalizes contact-term divergences differently from the contour deformation used in BCFT