feynlag.vertices.yangmills.quartic_couplings¶

feynlag.vertices.yangmills.quartic_couplings(group, physical=None, U=None)[source]¶

Rotated quartic tensor −g²/4 Σ_e F^e_ij F^e_kl per boson quadruple.

Returns:: dict {(V_i, V_j, V_k, V_l): coupling} where the coupling multiplies the (f·A·A)² contraction structure — i.e. the value of −g²/4 Σ_e F^e_ij F^e_kl for that ordered quadruple. The UFO writer assembles the three metric-pair structures from the ordered tensor (Phase 5).