We identify a curvature-dependent dimensionless control parameter ε (ℓ) = GD / (ℓD ℛ) that governs the consistency of semiclassical gravity when quantum probes are operationally localized in curved spacetime. The resulting breakdown scale is ℓ_* ∼ (ℓP^D-2 / ℛ) ^1/D. This short note supplies a unified leading-order EFT characterization of localization-induced backreaction in D spacetime dimensions. It recovers the familiar √ (ℓP Lcurv) form in D=4 while generalizing it covariantly and clearly states its mean-field limitations.
Devin Dodge (Thu,) studied this question.