Name: Xiu-Lei Ren (email_not_shown)
Date: 12/25/16-10:51:08 AM Z


Dear Vladyslav,

Thank you very much for your quick reply. It helps a lot.

However, when i try to obtain the analytic expressions of triangle diagram mentioned in the previous email, I also encountered two questions about PaXDiLog.

In order to avoid unexpected results when performing Dimension -> 4, I use the recommended FeynHelper--Package-X.

When I do this, the treatment of pave coefficient C0 is necessary.
In my case, (I am handling the two-nucleon scattering with two-pion exchange.
mN, mpi deonte as nucleon and pion masses, p4 is the momentum of outgoing nucleon, q is the transfer momentum between two nucleons.)

XC0 = C0[p4^2, q^2, (p4+q)^2, mN^2, mpi^2, mpi^2]

should be replaced by using

XC0Re = PaXEvaluate[XC0, PaXC0Expand -> True]//Normal

Apparently, the output is lengthy with conditions.

Then, perform the 1/mN expansion,

Series[XC0Re, {mN, infty, 0}]//Normal

The result always contains Li2 functions (PaXDiLog).

1) How one can transfer PaXDiLog to PolyLog?

Furthermore, when I do the numerical evaluation for checking,
I also find another problem about PaXDiLog.

2) e.g. PaXDiLog[Complex[-1,-6],-0.2], it cannot give a numerical value.

Could you kindly let me know how to handle these problem?

Merry Christmas and happy new year.

Cheers,
Xiu-Lei



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