Campbell, MarcNelson, Philip CWong, Eugene2023-05-232023-05-231991-11-012017-04-16https://repository.upenn.edu/handle/20.500.14332/43305We reconsider the problem of deforming a conformal field theory to a neighboring theory which is again critical. An invariant formulation of this problem is important for understanding the underlying symmetry of string theory. We give a simple derivation of A. Sen’s recent formula for the change in the stress tensor and show that, when correctly interpreted, it is coordinate-invariant. We give the corresponding superconformal perturbation for superfield backgrounds and explain why it has no direct analog for spin-field backgrounds.Electronic version of an article published as Int. J. Mod. Phys. A6, 6, 27, 1991, 4909-4924, 10.1142/S0217751X9100232X © [copyright World Scientific Publishing Company] http://www.worldscientific.com/doi/abs/10.1142/S0217751X9100232XPhysical Sciences and MathematicsPhysicsArticle