Gordon identities

[vsht]

GordonSimplify is a routine for applying Gordon identities to suitable spinor chains of vector or axial-vector current type.

• [x] Documentation
• [x] Unit tests
• [x] Spinor types, masses and momenta can be different
• [x] Chiral identities work with NDR and BMHV g^5 schemes
• [x] Extra identities that can be derived by sandwiching a sigma between two spinors should be added to DiracSimplify

Some comments regarding the additional identities.

Stuff like

SpinorUBar[p, m].GA[5].SpinorU[p, m] == 0
SpinorVBar[p, m].GA[5].SpinorV[p, m] == 0

is straightforward to add, but in D-dims only when using NDR.

But for identities similar to SpinorUBar[p, m].GA[mu].SpinorU[p, m] == FV[p, mu]/m SpinorUBar[p, m].SpinorU[p, m] we need a separate option: In some cases (e.g. when doing matching) one may not want to trade a vector current for a scalar current.