# Tag Info

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 ...
• 3,527

### Commutator of gamma matrices?

The $\gamma$ matrices are built-in, but undocumented, as InternalDiracGammaMatrix[]. Their indexing is also a bit different from the wiki page: ...

### 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 ...
• 3,527

### 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 ...
• 3,527

### 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 ...
• 240k
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 ...
• 3,527
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) ...
• 9,863

### V particle appearing in FeynArts/FeynCalc

You need to set the InsertionLevel option to {Classes} ...
• 3,527

### 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, ...
• 3,527

### 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,...
• 3,527
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 <...
• 3,527
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 ...
• 3,527