2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/187140The purpose of this work is to show that there exists an additional invariance of the $β$-function equations of string theory on $d+1$-dimensional targets with $d$ toroidal isometries. It corresponds to a shift of the dilaton field and a scaling of the lapse function, and is reminiscent of string field redefinitions. While it preserves the form of the $β$-function equations, it changes the effective action and the solutions. Thus it can be used as a solution generating technique. It is particularly interesting to note that there are field redefinitions which map solutions with non-zero string cosmological constant to those with zero cosmological constant. Several simple examples involving two- and three-dimensional black holes and black strings are provided to illustrate the role of such field redefinitions.LaTeX file, 15 pages, U. of Alberta report Alberta Thy-8-94. (Revisions consist of rewording the comment on the relationship of semiclassical and exact 2d black holes, including 2 references and expanding acknowledgement)High Energy Physics - TheoryGeneral Relativity and Quantum Cosmologytext