Feyman Rules for pi-pi scattering

[marti2216]

Hello, I have just starting working with the PHI package and I am trying to compute the Feynman Rules for a 4 pions vertex. I looked to the example given in the PhD thesis of Frederik Orellana but I did not get the same result and I do not understand why. I have basically copied the commands in that example but I get a lot of errors; already when I load FeynCalc I get the message that $Configurations and $Lagrangians appears in multiple context.

I attach my notebook where my code is written to a better comprehension of the problem.

Thanks in advance, Martin prova.pdf a

[vsht]

PHI is not really in a usable state, unfortunately. I'm not working on ChPT and since no one seems to use the package, there is not much motivation to do anything with it. And the reason people don't use it is probably that it is not 100% working, so it is a classical chicken and egg problem.

I fixed the particular issue you mentioned, but I have no idea what other issues may resurface if one tries more complicated things.

[vsht]

This should be how that code is supposed work.

PionVertex.zip

[vsht]

Of course, in general I don't mind fixing bugs in PHI and you are welcome to report more.

[vsht]

@marti2216

Hi Martina,

so, did this fix the problem for you? Or is there still something not working as it should?

Cheers, Vladyslav

[marti2216]

Thank you very much for your answers and availability!

Unfortunately I tried the script you sent me but, even if now I do not have the double definition of $Lagrangians and $Configuration in FeynCalc and Global, I don’t obtain any result. The problem is the covariant derivative that is written with a very strange index and when I go on with the computations Mathematica doesn’t know how to treat it and so I don’t get any result.

I attach the result I obtained by running your notebook for a better comprehension of the error I get.

Thank you very much again, Martina

Il giorno 25 apr 2022, alle ore 10:18, Vladyslav Shtabovenko @.***> ha scritto:

Of course, in general I don't mind fixing bugs in PHI and you are welcome to report more.

— Reply to this email directly, view it on GitHub https://github.com/FeynCalc/PHI/issues/1#issuecomment-1108233750, or unsubscribe https://github.com/notifications/unsubscribe-auth/ATNUBJ4BY6ZZHKSB52AHA4LVGZIMLANCNFSM5T7DSNXA. You are receiving this because you authored the thread.

[vsht]

Sorry, I should've mentioned that you need to run this on top of the latest development versions both for PHI and FeynCalc

https://github.com/FeynCalc/PHI#automatic-installation

https://github.com/FeynCalc/feyncalc/wiki/Installation#dev_automatic_installation

Once something has been pushed to the respective repositories, you'd need to reinstall them using the same scripts.

Cheers, Vladyslav

[marti2216]

Dear Vladyslav,

Thank you very much for your help and sorry for the very late replay. Now the error is fixed and all the input works.

Thanks again, Martina

Il giorno 11 ott 2022, alle ore 16:23, Vladyslav Shtabovenko @.***> ha scritto:

Sorry, I should've mentioned that you need to run this on top of the latest development versions both for PHI and FeynCalc

https://github.com/FeynCalc/PHI#automatic-installation https://github.com/FeynCalc/PHI#automatic-installation https://github.com/FeynCalc/feyncalc/wiki/Installation#dev_automatic_installation https://github.com/FeynCalc/feyncalc/wiki/Installation#dev_automatic_installation Once something has been pushed to the respective repositories, you'd need to reinstall them using the same scripts.

Cheers, Vladyslav

— Reply to this email directly, view it on GitHub https://github.com/FeynCalc/PHI/issues/1#issuecomment-1274776443, or unsubscribe https://github.com/notifications/unsubscribe-auth/ATNUBJZDCZJNPYNYANOIV7LWCVZ7TANCNFSM5T7DSNXA. You are receiving this because you were mentioned.