9 votes
Accepted

Distinguish FeynRules, FeynCalc, FeynArts, FormCalc and LoopTools

A typical 1-loop calculation can be roughly (I'm obviously oversimplifying things here) understood as a sequence of the following steps You write down the Largrangian of your model, e.g. QCD, QED, EW ...
vsht's user avatar
  • 3,507
7 votes

Using ModelMaker.m in FeynArts

AFAIK ModelMaker is not a very commonly used tool in model building. If you insist on using that, you probably should better contact Thomas Hahn directly. What people usually use in FeynRules. Here ...
vsht's user avatar
  • 3,507
6 votes

Commutator of gamma matrices?

The $\gamma$ matrices are built-in, but undocumented, as Internal`DiracGammaMatrix[]. Their indexing is also a bit different from the wiki page: ...
J. M.'s eventual burnout's user avatar
5 votes

Defining a two-index field in FeynCalc

You can define custom tensors in FeynCalc, but there is so not much you can do with them out of the box. Anyway, here is an example ...
vsht's user avatar
  • 3,507
5 votes

How much can we trust NIntegrate when NIntegrate::eincr is shown?

Introduction I'll give a generic answer to a generic question (and mostly ignore Cuba). What is supposed to happen in the global-adaptive strategy is that each recursive refinement, which subdivides ...
Michael E2's user avatar
  • 234k
4 votes
Accepted

Partial Derivative in FeynCalc

If you look at ?FieldDerivative you see that it contains following text NOTICE: FieldDerivative is defined only for objects with head \ QuantumField[...]. If ...
vsht's user avatar
  • 3,507
3 votes
Accepted

Working with Dirac Gamma Matrices using FeynCalc - A simple problem

If you just want to verify some identities of Dirac gamma matrices in some certain representations. FeynCalc is not a necessity. Actually your choice of Dirac matrices is just the Weyl (chiral) ...
Αλέξανδρος Ζεγγ's user avatar
3 votes

V particle appearing in FeynArts/FeynCalc

You need to set the InsertionLevel option to {Classes} ...
vsht's user avatar
  • 3,507
3 votes

FeynArts package fails to load

The problem is actually a very simple one: once FeynCalc has been loaded, you cannot reload it or load FeynArts, ...
vsht's user avatar
  • 3,507
3 votes

How to differentiate between superscript indices and powers in the output?

FeynCalc actually makes very little usage of ExplicitLorentzIndex. Such indices are not summed over but there are also no simplifications attached to them. Anyhow,...
vsht's user avatar
  • 3,507
3 votes
Accepted

Why FormCalc gives zero amplitude for this process

Although I have nothing to do with FormCalc, I think that I understand what is the problem here: Since you want to compute self-energy, you need to use the option <...
vsht's user avatar
  • 3,507
3 votes
Accepted

Implementing four-fermions operators on FeynRules and FeynArts

First of all you need to update to FeynCalc 9, FC 8.2 is already outdated. Please use the development version: https://github.com/FeynCalc/feyncalc/wiki/Installation#dev_automatic_installation I'm ...
vsht's user avatar
  • 3,507
2 votes

Feynarts not working

Provided that FeynArts was patched properly, which is mostly the case if the automatic installer is used, one can look at various examples involving FeynArts in the ...
vsht's user avatar
  • 3,507
2 votes

Definition of output C_00 and C_002 in FeynCalc

This is a Passarino-Veltman coefficient function, that appears when doing tensor decomposition of 1-loop integrals, see e.g. hep-ph/0509141 Often (especially for singular kinematics) one can define ...
vsht's user avatar
  • 3,507
2 votes
Accepted

FeynArts field insertion problem

You need to enable CKM mixing first. E.g. ...
vsht's user avatar
  • 3,507
2 votes
Accepted

contraction of indexes takes long time

General recommendations are Do not put intermediate instances of Contract, the function works best on the full expression Do not put momenta inside lists like <...
vsht's user avatar
  • 3,507
2 votes

Notebook doesn't open

After following the instrunctions here, e.g. by ...
Rolf Mertig's user avatar
  • 17.2k
2 votes

Can I specify the components of FourVector in FeynCalc?

I recently came across this problem as well. How I ended up calculating fully contracted amplitudes with explicit four-vectors (let it be momenta, polarization vectors) is as follows: Define the ...
Marvin's user avatar
  • 21
2 votes

FeynArts package fails to load

It worked after implementing a forced patch as mentioned in the wiki https://github.com/FeynCalc/feyncalc/wiki/FeynArts under Patching FeynArts for FeynCalc 9.x and above.
Subho's user avatar
  • 1,534
2 votes

Implementing four-fermions operators on FeynRules and FeynArts

You need to patch the model for use in FeynCalc: $LoadFeynArts=True; <<FeynCalc`; FAPatch[PatchModelsOnly -> True]
Logan Morrison's user avatar
2 votes

Cannot Install FormCalc on Linux

I encountered same error. Just notice 3 points :- 1. Check the file/folder permissions of FormCalc. Using ls -la in terminal. 2. Is form is installed or not? Form is required to run FormCalc using ...
Avi tomar's user avatar
2 votes
Accepted

Visual (apparently) bug with ComplexConjugate in FeynCalc

SetOptions[ComplexConjugate, FCRenameDummyIndices -> False] will not rename the repeated (dummy) indices.
Rolf Mertig's user avatar
  • 17.2k
2 votes

FeynCalc Commutator of Matrices

If I understand the question correctly, what you need is Inner[Dot, x, y] Here is an example of working with Dirac matrices by representing them as 2x2 matrices ...
vsht's user avatar
  • 3,507
2 votes
Accepted

What does the command '$FAVerbose = 0' do in FeynCalc

The option $FAVerbose is about how verbose the FeynArts will put out messages from functions that tell you their progress: <...
Shin Kim's user avatar
  • 1,271
2 votes

How do I NOT reduce loop integrals to one-point in FeynCalc?

You can disable partial fractioning (which is what reducing your denominator to A0), but most likely you will need to do it on a case-by-case basis ...
vsht's user avatar
  • 3,507
2 votes

Package-X has been terminated. FeynCalc and FeynHelpers not working

I think this one will work:::: https://data.mendeley.com/datasets/yfkwrd4d5t/1
Andre Luiz MB's user avatar
2 votes
Accepted

Package-X has been terminated. FeynCalc and FeynHelpers not working

This one also might be interesting https://gitlab.com/mule-tools/package-x
vsht's user avatar
  • 3,507
1 vote
Accepted

Feyncalc remove higher-order TensorFunction terms from expression

Do you mean something like this? ...
vsht's user avatar
  • 3,507
1 vote

Unexpected result when evaluating DiracGamma[5]

I think ComplexConjugate works on products of Dirac matrices assuming it is sandwiched between $u$ and/or $v$ spinors. Observe: ...
HirenPatel's user avatar

Only top scored, non community-wiki answers of a minimum length are eligible