Open ChiMaoShuPhy opened 2 years ago
I'm aware of this behavior, but I don't really see a way to fix this.
Functions that deal with spinor chains expect each spinor to depend on
a single momentum like p
or q
. This is mainly related to the way how FeynCalc
figures out whether the given Spinor
is a u, v, ubar or vbar. The sign of the momentum
is crucial here, cf.
https://feyncalc.github.io/FeynCalcBookDev/Spinor.html
Now if you make a spinor depend on a linear combination of momenta, all this machinery breaks down and one runs into very weird bugs, cf. https://github.com/FeynCalc/feyncalc/issues/76 The worst thing is that you'd get incorrect results without even noticing this. This is why I explicitly added a check to forbid such input.
For nonrelativistic expansions of spinor chains I advocate the approach where one first rewrites everything in terms of Pauli matrices and stuff (using FeynOnium routines) and then substitutes the decomposition of the heavy particles momenta with FCReplaceMomenta. This is how I handle this in my calculations.
`12.3.1 for Linux x86 (64-bit) (June 24, 2021)
9.3.1
Yes
no
SpinorUBar[p,m].SpinorU[p,m]//FermionSpinSum
worksSpinorUBar[p+k,m].SpinorU[p+k,m]//FermionSpinSum
reports errorFermionSpinSum: Error! FermionSpinSum encountered a fatal problem and must abort the computation. The problem reads: The input contains Spinor objects with incorrect syntax.
Same error was reported for
SpinorV
andSpinorVBar