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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63 views

How much can we trust NIntegrate when NIntegrate::eincr is shown? [closed]

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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50 views

How solve integral with three moment and delta function

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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47 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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88 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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29 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
40 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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30 views

FeynRules error: “Wrong head FC”, followed by “Filter” and $Aborted while trying to output UFO file

I've been trying to create the UFO files for a particular QCD Lagrangian, LQCD := LQuarkD + LUpS + LDownS + LSU3; to no avail. The ...
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1answer
245 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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35 views

FeynArts not throwing error, does not display diagram

I have the following diagram, but when I go to print, the output is the same as the actual topologylist. The topology list is ...
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59 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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44 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
119 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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56 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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52 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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50 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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32 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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76 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
128 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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63 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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36 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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77 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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113 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
279 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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324 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
121 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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64 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
156 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
83 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
263 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
206 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
70 views

Unexpected result when evaluating DiracGamma[5]

ComplexConjugate[DiracGamma[5]] // StandardForm returns -DiracGamma[5] Instead of simply ...
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2answers
298 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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69 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
1k 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
862 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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0answers
90 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
404 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
397 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
224 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
275 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
29 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
176 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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0answers
157 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
254 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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69 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
349 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
150 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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0answers
249 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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90 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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171 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 <...