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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17 views

Wrong contraction in Feyncalc when restrictions are imposed over the metric

I have the following tensor which I will manipulate in Feyncalc ...
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1answer
65 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 ...
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43 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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36 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) ...
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1answer
117 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 ...
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40 views

Vertex factor for effective field theory using Feynrules

Recently I have started learning "Effective Field Theory". As a part of learning, I was trying to calculate the vertex factor for a process where two unknown neutral spin-1 bosons $Y$ ...
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1answer
141 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 ...
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76 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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41 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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1answer
61 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: ...
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1answer
109 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 ...
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66 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 ...
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1answer
64 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: ...
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78 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 ...
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1answer
273 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)...
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65 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} ...
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59 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 ...
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203 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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57 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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1answer
103 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 ...
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1answer
819 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 ...
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92 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 ...
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72 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 ...
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1answer
232 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 ...
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76 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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75 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 ...
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175 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/...
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1answer
268 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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92 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 ...
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47 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 ...
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123 views

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 ...
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160 views

Summation over gamma matrices in a spin connection with FeynCalc

I need to construct the following object $\Gamma_{\mu} = \frac{1}{8} \omega_{\mu}^{ab}[\gamma_{a},\gamma_{b}]$ where $\omega_{\mu}^{ab}$ is object with space-time index $\mu$ and vierbeins index $a, ...
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1answer
543 views

Solving the Dirac equation in an arbitrary metric [closed]

I want to solve Dirac equation in a metric like $ds^2=g(u,v)\,du\,dv$. The relations of $u$ and $v$ with Minkowski coordinates $t$ and $x$ are given by functions $A$ and $B$, $t=A(u,v)$ and $x=B(u,v)$....
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1answer
648 views

Working with Dirac Gamma Matrices using FeynCalc - A simple problem

I need to obtain this using package FeynCalc: $$ \begin{align} [\gamma_{0},\gamma_{i}]=& 2 \gamma_{0}\gamma_{i}, \\ [\gamma_{i},\gamma_{0}]=& 2 \gamma_{i}\gamma_{0} , \\ [\gamma_{0},\gamma_{...
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1answer
173 views

V particle appearing in FeynArts/FeynCalc

I have the following problem. I am using Feynarts. I am running the following code: I am using QEDOnly. ...
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0answers
95 views

FeynCalc Notebook does not run

I've been trying to run an example of Chiral perturbation theory calculation. The notebook is from the site here. Every time I run the notebook, the InsertFields command throws up an error the says <...
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1answer
296 views

Is there a method in FeynCalc for collecting like powers of four vectors?

If I have a polynomial in some momentum $l^{\mu}$ such as $(q_1+l)^{\mu_1}(q_2+l)^{\mu_2}(q_3+l)^{\mu_3}...(q_n+l)^{\mu_n}$ in the numerator of an integral with measure $d^Dl$, is it possible to ...
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1answer
107 views

Feyncalc remove higher-order TensorFunction terms from expression

I am looking for a way to reduce the following expression: ...
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2answers
568 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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3answers
362 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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1answer
101 views

Unexpected result when evaluating DiracGamma[5]

ComplexConjugate[DiracGamma[5]] // StandardForm returns -DiracGamma[5] Instead of simply ...
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2answers
819 views

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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117 views

FeynArts: how to generate all the Feynman graphs for a given order of perturbation theory?

I am totally new to FeynArts Mathematica package and I am wondering if there is an opportunity to generate all (connected) Feynman graphs for a given order of perturbation theory? What I really want ...
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1answer
2k views

How to plot Feynman diagrams in Mathematica using FeynCalc and FeynArts?

I installed FeynCalc which automatically installs FeynArts: Import["https://raw.githubusercontent.com/FeynCalc/feyncalc/master/install.m"] InstallFeynCalc[] Now ...
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4answers
1k views

Commutator of gamma matrices?

Is the matrix $\sigma_{\mu\nu}$ $$\sigma_{\mu\nu} = \frac{i}{2} [\gamma_\mu, \gamma_\nu]$$ defined in FeynRules, FeynCalc or any similar packages? I know that $\gamma_\mu$ is ...
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94 views

Question for FeynRules: How to implement velocity dependent coupling

I am working with an extension of Standard Model which includes a fermionic field for the magnetic monopole. The photon-monopole coupling is velocity (beta = sqrt{1 - 4*monopoleMass^2/(s^2)} where ...
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1answer
687 views

Reduction of loop integrals in FeynCalc

I'd like to use the PaVeReduce function within FeynCalc in Mathematica to reduce a triangle integral down to bubbles and tadpoles. I found the wolfram help page about this function but I did not find ...
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1answer
548 views

Defining a two-index field in FeynCalc

I'm looking to define a two-index variable $h_{\mu \nu}$ in FeynCalc but the only examples of tensors with more than one index I've seen have been constants. Can a two-index variable be defined in ...
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1answer
243 views

contraction of indexes takes long time

I have got an expression which has more than a hundred terms being added up together, each of terms are similar in mathematical form....
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1answer
363 views

what to do when rule substitution doesn't work?

I got an expression expr = 1/SPD[{k1+k2-k},{k1+k2-k}] where ...