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.
85
questions
0
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0answers
17 views
Wrong contraction in Feyncalc when restrictions are imposed over the metric
I have the following tensor which I will manipulate in Feyncalc
...
0
votes
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 ...
1
vote
0answers
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 ...
1
vote
0answers
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) ...
0
votes
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 ...
0
votes
0answers
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 $Y$ ...
0
votes
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 ...
0
votes
0answers
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 ...
1
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0answers
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:
...
0
votes
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:
...
2
votes
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 ...
0
votes
0answers
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 ...
0
votes
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:
...
1
vote
0answers
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 ...
1
vote
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)...
1
vote
0answers
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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0answers
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 ...
1
vote
0answers
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 ...
1
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0answers
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
...
0
votes
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
...
4
votes
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 ...
1
vote
0answers
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 ...
1
vote
0answers
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 ...
1
vote
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 ...
0
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0answers
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, ...
0
votes
0answers
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 ...
0
votes
0answers
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/...
2
votes
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:
...
1
vote
0answers
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 ...
1
vote
0answers
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 ...
2
votes
0answers
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 ...
1
vote
0answers
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, ...
2
votes
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 $x=B(u,v)$....
1
vote
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_{...
1
vote
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.
...
0
votes
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
<...
1
vote
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 ...
1
vote
1answer
107 views
Feyncalc remove higher-order TensorFunction terms from expression
I am looking for a way to reduce the following expression:
...
1
vote
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 ...
1
vote
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 ...
1
vote
1answer
101 views
Unexpected result when evaluating DiracGamma[5]
ComplexConjugate[DiracGamma[5]] // StandardForm
returns
-DiracGamma[5]
Instead of simply
...
0
votes
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?
1
vote
0answers
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 ...
2
votes
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 ...
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
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 ...
3
votes
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 ...
2
votes
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 ...
2
votes
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....
1
vote
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 ...
