feynlag.vertices.vertex.classify_spins¶
- feynlag.vertices.vertex.classify_spins(field_tuple, spin_map)[source]¶
Vertex type string from the spins of the legs.
- Parameters:
field_tuple – physical field symbols.
spin_map –
{symbol: spin}with spin in {0, 1/2, 1}.
- Returns:
catalog key like
'VVS'(letters sorted V < S…, i.e. fermions first, vectors next, scalars last — FFV, VSS, VVS conventions).- Raises:
KeyError – a leg has no spin assigned.
ValueError – the spin content is outside the closed catalog.