# 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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### 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)...
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} ...
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 ...
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 ...
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 ...
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 ...
30 views

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 $x=B(u,v)$....
324 views

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 ...
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\...
I've installed the package (FeynArts, LoopTools, and FormCalc) via FeynInstall. Then, I load the package by <<FeynArts <<FormCalc I get message <...