feynlag.vertices.extract.extract_interaction_coefficients¶

feynlag.vertices.extract.extract_interaction_coefficients(L, fields, parameters=None)[source]¶

Extract interaction coefficients from a Lagrangian.

Tries a fast Poly-based method (domain='EX') first, falling back to a robust term-by-term method.

Parameters:

L – SymPy expression (the Lagrangian, or one sector of it).
fields – iterable of SymPy Symbol field components. Non-Symbol entries are ignored (fermion bilinears take the other track).
parameters – unused; kept for signature compatibility with DLRSM1.

Returns:

{n_fields: {sorted-field-tuple: coefficient}}.

Return type:

dict