Why General Relativity Appears in Perturbative String Theory: A careful MTT interpretation of worldsheet consistency and target-space dynamics

Abstract

The statement that General Relativity falls out of string theory is memorable but easy to misunderstand. A perturbative string background is described by a two-dimensional quantum field theory. Its couplings include the target-space metric, antisymmetric tensor, dilaton, and, in appropriate models, gauge and fermionic data. Requiring quantum Weyl consistency constrains these couplings. At leading order those constraints agree, after the required conventions and field redefinitions, with equations derived from a target-space effective action containing the Einstein-Hilbert term. Pure Einstein gravity appears only in a further low-energy and restricted field corner. This paper explains that chain without treating measurement, observation, or mathematical representation as physically privileged acts. It then gives the restrained Modal Triplet Theory (MTT) interpretation: the worldsheet and spacetime equations may be two diagnostics emitted by one preprojection source, but this is established only when explicit source maps and a controlled comparison square are constructed. The formal theorem is owned by the companion technical paper and is not repeated here. Current q79 work provides five of twelve worldsheet contract rows, partially provides two, and leaves five open. The result is therefore an explanatory bridge and a concrete completion program, not a proof that GR and string theory are the same theory or that MTT has already derived either one in full.