# 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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46 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 ...
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### How to represent the totally antisymmetric \[Epsilon] (Levi-Civita) tensor with a gamma matrix?

This is a result of mathematical output. I want the Eps at the end of the formula to be contracted with the gamma matrices at the front of the formula, and the final output is a series of gamma ...
31 views

### Feynman Rules in FeynCalc

I am trying to find the feynman rules with FeynCalc Package. K1 and K2 are the mésons $K^+$ and $K^-$ ...
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### 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 ...
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### 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: ...
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### How do you treat Longitudinally polarized massive vector bosons (W, Z bosons) separately in the FeynCalc package?

This is a question pertaining to the FeynArts and FeynCalc package of Mathematica. I am trying to compute Standard Model cross-sections for Electroweak processes. For the interactions I am looking at, ...
1 vote
48 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/...
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### 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
52 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 ...
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1 vote
104 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) ...
227 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 ...
314 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 ...
159 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 ...
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1 vote
59 views

### Apply Formula automatically in Feyncalc

I want to apply the function Tdec in Feyncalc automatically. Here is an example what the input is: ...
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### 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: ...
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### 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 ...
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### 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 ...
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### 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: ...
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### 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
515 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
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### 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} ...
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### 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 ...
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1 vote
266 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 ...
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1 vote
68 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 ...
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### 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 ...
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### 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 ...
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118 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
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### 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
344 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 ...
89 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, ...
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### 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 ...
203 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/...
379 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: ...
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### 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 ...
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### 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 ...
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### Antiparticles in Feynrules Lagrangian

I am trying to implement a simple extension of the SM to Feynrules, generating the Lagrangian in a Mathematica notebook file. I am wondering about the following: Is there a way to explicitly use the ...
1 vote
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### Feyncalc remove higher-order TensorFunction terms from expression

I am looking for a way to reduce the following expression: ...
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787 views

### FeynArts package fails to load

This is definitely a duplicate of FeynArts not working properly. However, that post dates back 5 years. I am currently on Mathematica 11.0.1.0 with Windows 10 as my OS. I have been trying to load the ...
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1 vote
502 views

### Replace on FeynCalc

I can do replacements easily using /. p = {1, 2, 3}; //in input = 4 Overscript[p, _]^2 /. {Overscript[x_, _]^2 -> x.x} //in 56 //Out However, using the same ...
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112 views

### Unexpected result when evaluating DiracGamma

ComplexConjugate[DiracGamma] // StandardForm returns -DiracGamma Instead of simply ...
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### Can I specify the components of FourVector in FeynCalc?

I'm using FeynCalc to calculate Compton's scattering. I need to use specific values for the components of the photon polarization four-vector. How can I do that?
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