# Questions tagged [feyncalc]

Questions about Mathematica packages for High Energy Physics and Quantum Field Theory, e.g. FeynCalc, FeynArts, FormCalc, FeynRules, HEPMath, Package-X, LoopTools, Tracer etc.

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### Problems in generating example models of FeynCalc

I'm getting started with FeynCalc and FeynArts, so I tried to run some of the examples they give you. Everything works fine, except for the ones which require to generate a model using the scripts in ...
55 views

### LiteRed Package for Feynman Integral

<< LiteRed(Loading the package) SetDirectory[NotebookDirectory[]] SetDim[d]; These commands I am using to load the package 1.83 LiteRed. Though, it is prompting as cannot open LiteRed. Any ...
91 views

### Simplification of Momentums in FeynCalc

I have a little problem involving the following contraction in FeynCalc: $$\frac{k^{\delta}k^{\sigma}}{k^2}$$ By hand one would lower $\sigma$ and contract with the other momentum to cancel $k^2$, ...
57 views

### FeynCalc Kronecker delta contraction

I want to simplify some expressions like a[i]*b[i]*KD[i,j]. After contraction, it should be a[j]*b[j], but it seems that FeynCalc cannot handle more than 3 of the same CartesianIndices. I know for ...
72 views

### Working with Vertex Functions in FeynArts

FeynArts supports in its current version 3.11 the use of vertex functions in Feynman diagrams. As described in the manual, one can create topologies with generic vertex functions using the function <...
1 vote
106 views

### How can I use FeynCalc in ParallelTable or ParallelSum?

I want to speed up a FeynCalc calculation. However I found out that it doesn't seem to work in ParallelSum or ParallelTable. MWE:...
1 vote
108 views

### Hermitian Adjoint of Gamma matrices in FeynCalc

I expected the following code: GA . ConjugateTranspose[GA[μ]] . GA to return GA[μ], since it's a fundamental property of ...
1 vote
73 views

### Feynman Rules in FeynCalc

I am trying to find the feynman rules with FeynCalc Package. K1 and K2 are the mésons $K^+$ and $K^-$ ...
1k views

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

I want to compute the finite parts of 1-loop integrals using FeynCalc. One of the most important package used for this is FeynHelpers (which in it uses Package-X). But, since July 1, 2022, Package-X ...
117 views

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

So I am doing a box integral, the amplitudes look like this: I do the loop integration of it using the following code: ...
124 views

103 views

### Field derivatives in FeynCalc

I am using the latest version of both Mathematica and FeynCalc. I'm trying to obtain the Feynman rules for a theory with derivative interactions. Following https://www.feyncalc.org/FeynCalcBook/...
240 views

### FeynCalc Commutator of Matrices

I am trying to learn how to use FeynCalc to handle commutators in Mathematica, but I can't seem to figure out how to take the commutator of two matrices with entries made up of products non-commuting ...
1 vote
81 views

### Can FeynCalc be used for Heavy quark effective field?

I start to learn FeynCalc. I want to use it for Heavy quark field theory. For example, extract the vertices from Eq.(34) from paper 1901.10339. Since I am not good at FeynCalc, so I want to know ...
1 vote
307 views

### Exclusion of particular vertices in FeynArts

I am trying to generate diagrams for H -> ZZ process at one loop level. I only want these 5 diagrams in the final output given by (T1 P1 N1), (T1 P2 N2), (T8 P1 N12), (T9 P1 N14), (T10 P1 N16) ...
459 views

### Feynrules + FeynArts - Calculating amplitudes

I am working on a model which is an extended model of the standard model (SM + Complex Scalar Field). I am using FeynCalc (9.0.3) patched with FeynArts (3.11). I run ...
633 views

### How to Contract Indices Using Feyncalc

I am slowly learning how to use Feyncalc, and I have a quick question. I have a third rank tensor B[mu,nu,tao] and I also have a four-vector FV[W,mu]. I would like to contract the first two indices ...
321 views

### Easiest way to export amplitude from FeynArts to FeynCalc

I am having trouble calculating some unpolarized squared amplitudes with FeynArts+FormCalc and want to use FeynCalc to manually handle the amplitudes calculated by FeynArts. What is the easiest way to ...
1 vote
72 views

### Apply Formula automatically in Feyncalc

I want to apply the function Tdec in Feyncalc automatically. Here is an example what the input is: ...
272 views

### FermionSpinSum in FeynCalc

I have to evaluate the spin chains as described in the following PSE question. To that end, in FeynCalc, I have done the following: ...
195 views

### Tensor Algebra Problem

I am just getting started with tensor algebra using Mathematica. I could use some help with a simple problem I am starting with at my website: http://www.tifis.org/mathematicaproblem.pdf An ...
139 views

### Feyncalc Chain re-ordering problem

I am encountering a similar problem with much more complex terms than the ones shown in the figures below. Basically, I wrote the chain for a process(in this case, a simple 2 particle scattering in ...
193 views

### Visual (apparently) bug with ComplexConjugate in FeynCalc

When I use ComplexConjugate in Feyncalc, if there are repeated indices in its argument, a visual bug occurs. The most minimal example would be: ...
1 vote
127 views

### Dirac Operator in de Sitter background

I am attempting to write the Dirac operator in a curved background, and eventually solve the equation as a second order PDE, since I am attempting to bring it into Klein-Gordon form. Essentially what ...
1 vote
790 views

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

I have been dealing with a high oscillation integration using NIntegrate. The warning of eincr shows that no matter how large (X)...
1 vote
77 views

### How solve integral with three moment and delta function [closed]

I am trying solve this integral in mathematica: \begin{equation} \int \dfrac{d^3 p_3}{(2\pi)^3 2 E_3} \dfrac{d^3 p_4}{(2\pi)^3 2 E_4}(p_1 p_2)(p_3 p_4) \delta (p_3 + p_4 - p_1 - p_2). \end{equation} ...
69 views

### How to properly evaluate a Green's equation in FeynCalc (or any other package)?

In 4D, the Green's function of the box operator with respect to $p$ is $1/p^2$,i.e. $$\partial_p^2 \frac{1}{p^2} = -(2\pi)^2 \delta^{(4)}(p). \tag{1}$$ I use the package FeynCalc, in which the ...
1 vote
377 views

### Calculating Amplitudes with FeynArts

I'm following a lecture on how to use FeynCalc, FeynArts, I have done exactly what they say to me to do. Everything was going ok until that point. FeynArts is not calculating amplitudes, error message ...
1 vote
107 views

### Feyncalc : problem with diracreduce/diracsimplify. BUG?

I am new to Feyncalc and I am facing the following problem. I am doing the following: I set q3=-q2-q1; Then I write ...
1 vote
227 views

### How to evaluate an expression with FeynCalc?

How can I evaluate specific expressions in FeynCalc? For example, if there is a $\delta^i_j$, how can I set $i$ to 1 and $j$ to 2 and make it evaluate to zero? I've tried ...
2k views

### Distinguish FeynRules, FeynCalc, FeynArts, FormCalc and LoopTools

I am totally confused: I can't distinguish the packages FeynRules, FeynCalc, FeynArts, FormCalc, LoopTools properly. Once I installed FeynRules I think. It seems to include the packages FeynCalc and ...
1 vote
168 views

### FeynArts is not plotting Propagator labels/fields

I am trying to use FeynArts to generate two feynman diagrams (one for electron scattering, and one for higgs->bb w/ VGF). On the first I can't seem to figure out how to get labels or arrows, not get ...
1 vote
128 views

### Need to use FeynArts to determine Feynman diagrams of a process with initial particles having no masses

so i'm facing this problem in using FeynArts, i need to find the feynman diagrams of a process with intial particles not having masses, but i can't find the command to use to declare particles as ...
1 vote
466 views

### Cannot Install FormCalc on Linux

so i tried to install FormCalc on linux and when i run the compile command i get "cannot determine mathematica's system ID using_/usr/local/bin/math" Has anyone encountered such error and is there a ...
1 vote
123 views

### Simplify GA[a].GA[b]+GA[b].GA[a] to 2 MT[a,b]

Does a FeynCalc command exist, that simplifies the expression GA[a].GA[b]+GA[b].GA[a] to 2 MT[a,b] I've tried Calc, ...
113 views

### Why does Null appear in Contract and Pair commands of FeynCalc?

I started now to use FeynCalc on Mathematica 10. The installation looks like okay, but every time I use Contract or Pair commands the output is something with "Null". Even in this simple case, for a ...
245 views

### FeynCalc example — muon decay — integration issue

I'm just starting out using Mathematica and I'm trying to work through one of the examples given for FeynCalc, specifically the muon decay: https://github.com/FeynCalc/feyncalc/blob/master/FeynCalc/...
526 views

### FeynCalc: FermionSpinSum problems with interference of diagrams

I encountered a problem in FeynCalc, where i wanted to calculate the $\sum_\text{spins}|\mathcal{M}|^2$ of a process and therefore need the function FermionSpinSum[ ] of FeynCalc. I run: ...
1 vote
182 views

### Abstract derivatives in Feyncalc

I have encountered several problems regarding the application of formal derivative operators in FeynCalc, using the built-in function FCPartialD, Left/RightPartialD Schematic description of my ...
1 vote
51 views

### How to represent Dirac matrices in general $n$ dimensions in mathematica? [duplicate]

I want to represent Dirac matrices in $N$ dimensions in Mathematica like we have for the Pauli matrices, i.e. PauliMatrix[i], {i,1,3} I guess there must be some ...