Brane-Bulk Throat Ontology for a Superfluid Defect Toy Universe

This paper, the fifth in a series developing a “superfluid defect toy universe,” resolves the geometric tension between the model’s gravitational and electromagnetic sectors. Previous work established that reproducing 1PN gravity requires defects to behave as spherical sinks, whereas the electromagnetic sector requires cylindrical resonant cavities. We resolve this apparent contradiction by promoting defects to brane–bulk throats connecting the observable 3D brane to a 4D superfluid bulk. Dimensional reduction reveals that the far–field potential on the brane is monopolar, with angular corrections from the throat geometry suppressed by (a/r)². Numerical integration of a representative hard-bounded “rounded funnel” throat geometry confirms this suppression, yielding a leading quadrupole coefficient α₂ ≈ 1.4 × 10⁻² (for L/a = 2 and a 10% quadrupolar anisotropy), thereby robustly recovering the spherical sink approximation for 1PN gravity. Inside the throat, however, 4D acoustic modes separate into cylindrical Bessel profiles; enthalpy minimization of these modes at fixed charge selects the preferred aspect ratio L/a ≈ 1.85 found in the electromagnetic construction. We further show that long-range magnetostatics can arise without bulk vorticity by identifying the magnetic field with the vorticity of a brane-confined transverse wake sourced by the motion of a charged throat. Finally, we incorporate the corrected wake–mixing constraint α² = ¾ from Paper III as a real, positive-definite longitudinal/transverse weighting in the vector sector once the wake basis is completed. This ontology constrains finite-size effects, laying the groundwork for falsifiable 2PN predictions.