The two-loop g−2 coefficient C₂ = −0. 328478966 is derived directly from foam topology without QED as intermediary. All four terms of the Petermann-Sommerfield formula are derived: 197/144 from wavefunction renormalization Z₂ plus face graph counting; π²/12 from two D-mode loop phases normalised by Ngauge=12; −π²ln2/2 from the Eg threshold √ (CA+1) =2; and 3ζ (3) /4 from T₂g winding harmonics Σ1/n³=ζ (3) weighted by CA/λEg=3/4. Apéry's constant enters not from a Feynman integral but from π₁ (T₂g) =ℤ. Agreement: 3×10⁻¹⁶. Zero free parameters.
Luke Martin (Wed,) studied this question.