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.
77
questions
0
votes
0answers
29 views
FeynArts & FeynRules: Duplicate components in KinematicVector(F,F,F,F)
When using my custom model in FeynArts I get the message
InitializeModel::dup : "Duplicate components in KinematicVector(F,F,F,F)"
The term causing this in the lagrangian is
$$((\partial^\mu \bar\...
0
votes
0answers
46 views
Feyncalc Chain re-ordering problem
I am encountering a similar problem with much more complex terms than the ones shown in the figures below. Basically, I wrote the chain for a process(in this case, a simple 2 particle scattering in ...
0
votes
1answer
31 views
Visual (apparently) bug with ComplexConjugate in FeynCalc
When I use ComplexConjugate in Feyncalc, if there are repeated indices in its argument, a visual bug occurs. The most minimal example would be:
...
1
vote
0answers
59 views
Dirac Operator in de Sitter background
I am attempting to write the Dirac operator in a curved background, and eventually solve the equation as a second order PDE, since I am attempting to bring it into Klein-Gordon form. Essentially what ...
1
vote
1answer
132 views
How much can we trust NIntegrate when NIntegrate::eincr is shown?
I have been dealing with a high oscillation integration using NIntegrate. The warning of eincr shows that no matter how large (X)...
1
vote
0answers
53 views
How solve integral with three moment and delta function [closed]
I am trying solve this integral in mathematica:
\begin{equation}
\int \dfrac{d^3 p_3}{(2\pi)^3 2 E_3} \dfrac{d^3 p_4}{(2\pi)^3 2 E_4}(p_1 p_2)(p_3 p_4) \delta (p_3 + p_4 - p_1 - p_2).
\end{equation}
...
0
votes
0answers
51 views
How to properly evaluate a Green's equation in FeynCalc (or any other package)?
In 4D, the Green's function of the box operator with respect to $p$ is $1/p^2$,i.e.
$$\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
0answers
114 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
0answers
39 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
...
0
votes
1answer
61 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
...
0
votes
0answers
36 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
...
3
votes
1answer
388 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 ...
0
votes
0answers
37 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
...
1
vote
0answers
69 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
0answers
51 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
1answer
152 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 ...
0
votes
0answers
61 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, ...
0
votes
0answers
60 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 ...
0
votes
0answers
106 views
FeynCalc example ā muon decay ā 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/...
2
votes
1answer
164 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
0answers
70 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
0answers
41 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 ...
2
votes
0answers
87 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 ...
1
vote
0answers
126 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, ...
1
vote
1answer
352 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)$....
1
vote
1answer
422 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_{...
1
vote
1answer
140 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.
...
0
votes
0answers
79 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
<...
1
vote
1answer
188 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 ...
1
vote
1answer
90 views
Feyncalc remove higher-order TensorFunction terms from expression
I am looking for a way to reduce the following expression:
...
1
vote
2answers
323 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 ...
0
votes
1answer
242 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 ...
1
vote
1answer
92 views
Unexpected result when evaluating DiracGamma[5]
ComplexConjugate[DiracGamma[5]] // StandardForm
returns
-DiracGamma[5]
Instead of simply
...
0
votes
2answers
433 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?
1
vote
0answers
87 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 ...
2
votes
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 ...
4
votes
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 ...
0
votes
0answers
92 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 ...
3
votes
1answer
504 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 ...
2
votes
1answer
450 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 ...
2
votes
1answer
228 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....
1
vote
1answer
306 views
what to do when rule substitution doesn't work?
I got an expression
expr = 1/SPD[{k1+k2-k},{k1+k2-k}]
where ...
0
votes
0answers
31 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 ...
0
votes
1answer
191 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 Ńode:
...
0
votes
0answers
179 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=Ī¾ but it does not work.
How to change gauge in these packages?...
5
votes
1answer
327 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 ...
0
votes
0answers
72 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 ...
1
vote
1answer
373 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
...
0
votes
1answer
158 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
...
1
vote
0answers
275 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\...
