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.
68
questions
0
votes
0answers
29 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
50 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 ...
0
votes
0answers
28 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 ...
0
votes
0answers
40 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
52 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
42 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
34 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
...
0
votes
0answers
26 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 ...
0
votes
0answers
36 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/...
2
votes
1answer
74 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
57 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
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 ...
2
votes
0answers
65 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
97 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
207 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 $x=B(u,v)$....
0
votes
1answer
243 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
101 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
59 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
133 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
79 views
Feyncalc remove higher-order TensorFunction terms from expression
I am looking for a way to reduce the following expression:
...
1
vote
2answers
200 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
163 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
64 views
Unexpected result when evaluating DiracGamma[5]
ComplexConjugate[DiracGamma[5]] // StandardForm
returns
-DiracGamma[5]
Instead of simply
...
0
votes
1answer
192 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
57 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
878 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
684 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
78 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 ...
2
votes
1answer
314 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
343 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
216 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
239 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
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 ...
0
votes
1answer
167 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:
...
0
votes
0answers
133 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?...
5
votes
1answer
215 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
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 ...
1
vote
1answer
303 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
138 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
219 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\...
0
votes
0answers
88 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 ...
0
votes
0answers
165 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
<...
1
vote
1answer
205 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
...
1
vote
0answers
226 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
...
2
votes
1answer
192 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
...
1
vote
1answer
326 views
FeynRules and defineing lagrangian
We are going to add new term to Standard Model, I defined a new vector field
...
1
vote
1answer
91 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 ...
5
votes
1answer
551 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 ...
2
votes
1answer
267 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 ...
1
vote
0answers
106 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 $SU(3)_F$...
