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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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24 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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31 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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45 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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38 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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30 views

FeynRules Dirac structures

I am currently working on an effective theory and want to implement the operators into Feynrules-> FeynArts, etc. I use the normal SM.fr file except for the extra term ...
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23 views

problem with FeynCalc abbreviations

I am new in feyncalc and I am trying to do a one loop calculation using feynarts-feyncalc. In my final passarino-veltman reduced result I've got coefficients "gc7,gc11,gc9" I guess these are ...
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30 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
60 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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53 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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0answers
29 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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58 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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90 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
177 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
196 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
91 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
56 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
115 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
73 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
170 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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1answer
146 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
61 views

Unexpected result when evaluating DiracGamma[5]

ComplexConjugate[DiracGamma[5]] // StandardForm returns -DiracGamma[5] Instead of simply ...
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1answer
168 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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56 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
781 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
631 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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75 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
295 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
310 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
204 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
233 views

what to do when rule substitution doesn't work?

I got an expression expr = 1/SPD[{k1+k2-k},{k1+k2-k}] where ...
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0answers
26 views

Selecting few arrays from a list and displaying their content

I am using FeynHiggs package on Mathematica 11 to calculate fermion masses in MSSM. Function FHGetPara[] returns a list that ...
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1answer
163 views

Notebook doesn't open

I have a notebook with my program. It works whit package FeynCalc. At the latter work with this document, I wrote the сode: ...
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122 views

How to set gauge in FeynCalc?

I want to set gauge in all of my calculation with FeynArts and FeynCalc to $\xi$ gauge. I use $Gauge=ξ but it does not work. How to change gauge in these packages?...
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1answer
197 views

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

I have ambiguous notation in my output. I have output that has two types of superscripts, indices and powers. The indices range from {none,0,1,2,3} and typical powers are 2 or 4. When there is an ...
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66 views

How to use Neglect function in FormCalc?

I am trying to calculate amplitude from Feynman diagram with FormCalc package and I want to set mass of external particle to be zero which I found that I have to use "Neglect". However, I can't find ...
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1answer
292 views

FeynCalc does not simplify Spinor relations

Is there a reason why sometimes FeynCalc does not simplify expressions that looks very simple like $$\bar{u}^s(p,m).u^s(p,m). $$ This does not happen all the time, eg. if I simply input ...
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1answer
137 views

Definition of output C_00 and C_002 in FeynCalc

When I am using FeynCalc, I am getting an output as follows: Subscript[C, 00](0,Overscript[p, _]^2,Overscript[p, _]^2,0,0,0) and ...
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209 views

Inserting Lorentz vectors in Lagrangian in FeynRules

I am writing the model file for an effective theory. The lagrangian of the theory has an external physical lorentz vector (say velocity in Heavy Quark Effective Theory where the Kinetic part is $\bar\...
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82 views

Expressing the output product using dot

I have an expression of the form Hbar.H where H and Hbar are vectors. How can I get the ...
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163 views

How long does it take to load FormCalc package?

I've installed the package (FeynArts, LoopTools, and FormCalc) via FeynInstall. Then, I load the package by <<FeynArts` <<FormCalc` I get message <...
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1answer
194 views

FeynArts field insertion problem

I'm trying insert this scattering into FeynArts as kaon decay (Up quark and anti strange quark to anti muon and neutrino ): but can't figure out why no field enter into 2->2 topologies ...
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209 views

Now why LoopTools do not make calculation

In deed I still in calculating the self energy diagram I started in this post Why FormCalc gives zero amplitude for this process Here is the code I use after the last answer ...
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1answer
186 views

Why FormCalc gives zero amplitude for this process

Why when I generate self energy diagram of for neutrinos, FormCalc gives zero amplitude ? here is the code ...
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1answer
311 views

FeynRules and defineing lagrangian

We are going to add new term to Standard Model, I defined a new vector field ...
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1answer
88 views

LeviCivita::shdw when I am loading FeynCalc

I have downloaded FeynArts-3.9 and put it in Applications already. Then, I downloaded FeynCalc using Import[]. After that, I used ...
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1answer
512 views

Using ModelMaker.m in FeynArts

I want to write a model file in FeynArts and I came across ModelMaker which takes in the Lagrangian as Input and then generates the .mod file. I am trying to make a model file for $\phi^4$ theory as a ...
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1answer
262 views

FeynCalc capability in Beyond Standard Model

Few days ago I started to learn FeynCalc, but it seemed to me that it has not capability of handling new models, thus I quit. It seemed that it just loads some predefined Lagrangians. My questions ...
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103 views

Adding a global SU(3) flavor-symmetry in FeynRules

I would like to add the operators $$ \bar{d}_R \gamma^\mu T^F d_R G^F_\mu $$ $$ \bar{d}_R \gamma^\mu T^FT^C d_R G^{FC}_\mu $$ in a model of FeynRules, where $F$ is the adjoint index of the $SU(3)_F$...
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1answer
253 views

Implementing four-fermions operators on FeynRules and FeynArts

I am trying to implement operators of the form $$ \bar{q}_L \gamma^\mu T^A q_L \bar{q}_L \gamma_\mu T^A q_L $$ where T^A are the SU(3) generators and $q_L$ is the Electroweak SU(2) doublet. I use ...
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71 views

Quits Kernel during evaluation of CreateTopologies

I am using Feynarts 3.9 and FeynCalc 9.0.1 with Mathematica 10. Every time I load FeynArts with FeynCalc and execute t = CreateTopologies[1, 1 -> 2]; ...