feynlag.vertices.bilinear.majorana_mass_matrix

feynlag.vertices.bilinear.majorana_mass_matrix(L_fermionic, field_base, vacuum, nflavors, indices, gamma=None)[source]

Symmetric Majorana mass matrix from the vacuum-evaluated sector.

Collects the coefficient of MajoranaBilinear(field_base[i], CΓ, field_base[j]) at the vacuum for a Lagrangian mass term written in the convention L ⊃ −½ M_ij ψ_iᵀ C ψ_j (so M[i,j] = −2·coefficient). Because MajoranaBilinear canonicalises its legs (the i↔j Grassmann symmetry), each unordered flavour pair contributes exactly one atom, and the returned matrix is symmetric by construction — ready for diagonalize_takagi().

Parameters:

  • L_fermionic – the (Weinberg / bare-Majorana) sector, weak basis.

  • field_base – the IndexedBase of the Majorana field (both legs).

  • vacuum – Vacuum.

  • nflavors – matrix dimension.

  • indices – kept for backward compatibility and ignored — each term is read at its own leg indices (symbolic, integer or repeated), as in fermion_mass_matrix().

  • gamma – restrict to one middle structure (default: sum all).

Returns:

nflavors × nflavors symmetric Matrix.