feiyang472 / feynwrap.py

Generate simple Feynman diagrams easily with python. Written for Cambridge Part II Particle Physics introductory course.

feynwrap.py

Purpose: Writing tikz makes me sad, so I wrap a layer of python around it to allow continuous creation of vertices and edges in Feynman diagrams.

Installation

git clone https://github.com/Feiyang472/feynwrap.py.git

cd feynwrap.py

pip3 install .

Drell-Yan example

from feynwrap import vert

vert('q').br().bl(r'\bar{q}',True).ppgt(r'\gamma', 'boson').br('l',True).ar('anti fermion',r'\bar{l}', True)

vert.save_tex('demo.tex', path='./examples/')

vert.compile_pdf()

Result

Tutorial

The first method is always vert, which creates a vertex. We can give it a label, and/or specify its location with respect to another vert instance.

a = vert('\lambda')

The label $\lambda$ will be put on this just created vertex. Now we can get a propagator from a, and retrieve the vertex where the propagator arrives.

b = a.ppgt()
b.ppgt('fermion')
b.ppgt('below right', 'boson').ppgt('below left', 'gluon' True).ppgt('e', 'below right')

The propagate method takes 0 to 4 arguments in any order. It recognizes special strings specifying particle type ('anti fermion', 'boson', 'gluon' etc.) and relative locations ('above left' etc.), as well as a Boolean value which specifies whether the destination of this propagation is at ends of the diagram.

At ends of the diagram, propagator labels are put on vertices. Otherwise, they are put alongside the edges.

The program then allows us to save to a .tex file and build it to pdf. The associated .aux and .log files are always removed after build.

vert.save_tex('demo.tex', path='./examples/')
# vert.save_tex('demo', path='./examples/') # is exactly the same

vert.compile_pdf() 

If you want to keep the tex file and make some edits, specify clean=[] in compile_pdf.

---

This is an example of the generated .tex.

\begin{tikzpicture}
\begin{feynhand}
\vertex (v1)  {\(q\)};
\vertex (v2) [below right = of v1] ;
\vertex (v3) [below left = of v2] {\(\bar{{q}}\)};
\vertex (v4) [right = of v2] ;
\vertex (v5) [below right = of v4] {\(l\)};
\vertex (v6) [above right = of v4] {\(\bar{{l}}\)};

\propag [fermion] (v1) to (v2);
\propag [fermion] (v2) to (v3);
\propag [boson] (v2) to [edge label = \(\gamma\)] (v4);
\propag [fermion] (v4) to (v5);
\propag [anti fermion] (v4) to (v6);
\end{feynhand}
\end{tikzpicture}