We present a controlled effective-field-theory (EFT) description, valid at intermediate scales r ≳ rcut, in which a single non-minimal curvature–gauge operator (α/MP²) Rℱ, coupling spacetime curvature to a Standard-Model gauge field, deforms an exact, overcharged (M < Qₘ) magnetically charged Reissner–Nordström background at intermediate (sub-Planckian, trans-particle) scales. The single dimensionless coupling |α| ∼ 10⁻⁶ lies deep inside the EFT convergence domain (R/MP² ∼ 10⁻³) and satisfies all current experimental bounds. Working in the controlled O (α) expansion about the exact Einstein–Maxwell seed, we (i) derive the interaction energy–momentum tensor exactly (Theorem 1) ; (ii) prove that the Dirac magnetic-monopole ansatz remains an exact solution of the modified gauge equations on any static spherically symmetric background (Theorem 3) ; and (iii) compute the resulting O (α) metric deformation with a complete, openly archived numerical solver that runs end-to-end and reproduces every table and figure reported here. We are deliberately precise about what the geometry is and is not. It is a horizonless (the overcharged condition removes all horizons), singly-asymptotic compact geometry whose metric potential N (r) = 1 − b/r attains a minimum at r₀ = Qₘ²/M — a curvature-supported redshift neck, not a Morris–Thorne throat: the areal radius decreases monotonically to r = 0, gᵣr stays finite (b/r < 1 everywhere), and there is no minimum-areal-radius surface and no photon sphere. The overcharged seed retains a naked curvature singularity at r = 0, which lies outside the EFT-controlled region r ≳ rcut ∼ few MP⁻¹; we make no regularity claim there, and a globally regular, non-perturbative completion is identified as the central direction for future work. Central claim. The genuine, defensible content of this work is not the discovery of a new geometric feature — the neck belongs to the overcharged Reissner–Nordström seed — but rather that a single, Standard-Model-compatible, dimension-six operator produces a controlled, sign-definite O (α) deformation of that geometry with (a) a finite open window of linearly stable couplings under reflecting inner boundary conditions, and (b) one falsifiable near-term observational handle: an inflationary CMB scalar–tensor correlation C_ℓ^ST. We report the stability result honestly as linear radial and dipole stability under a reflecting inner boundary condition over the window −8 × 10⁻⁶ < α < −2 × 10⁻⁷, not as a global stability theorem. Two further channels — a small-scale CMB lensing imprint τwh and a parametrically unobservable tensor-mode dispersion shift (δvg/c ∼ 10⁻⁸⁹) — are presented uniformly as order-of-magnitude forecasts. The present EFT description is valid for r ≳ rcut.
Arsalan Zeynali (Sat,) studied this question.