2

The following code,

\documentclass{article}
% lualatex

\usepackage{tikz-feynman}
\begin{document}

\begin{figure}[h!]
\centering
\begin{align}
\feynmandiagram [inline=(b), horizontal=a to b, layered layout] {
    a -- [blue, gluon] b [dot] 
    -- [blue, gluon, loop, min distance=1cm] b -- [blue, gluon] c};   
\end{align}
\end{figure}
\end{document}

is producing the following Feynman diagram:

enter image description here

I find this loop a bit ugly and I believe that there is a way to make it look better. Can anyone give me improvement suggestions to make it more elegant and appealing?

2
  • 2
    You will have a lot more success getting an answer, if you post separate questions for the separate problems. Edit your code to be compilable and contain only one diagram and ask about that one diagram. Jan 6, 2023 at 2:58
  • You are right. I am starting from the most problematic one, the tadpole. Thanks!
    – Tr909T
    Jan 6, 2023 at 17:20

2 Answers 2

3

The TikZ coil will never be beautiful with tight bends. I see no other way than to plot the coil. Here I have made a somewhat involved style. It would also a possibility to simply draw it afterwards.

\documentclass[tikz, border=1cm]{standalone}
\usepackage[compat=1.1.0]{tikz-feynman}
\tikzset{
gluontad/.style={
append after command={
\pgfextra
\begin{pgfonlayer}{background}
\draw[shift=(\tikzlastnode), #1] plot[domain=-90:270, samples=200, smooth, variable=\a] ({0.3*cos(\a)+0.06*cos(15*\a)},{0.3*sin(\a)+0.3+0.06*sin(15*\a)});
\end{pgfonlayer}
\endpgfextra
}}}
\begin{document}
\begin{tikzpicture}
\pgfdeclarelayer{background}
\pgfsetlayers{background, main}
\begin{feynman}
\diagram[inline=(b), horizontal=a to b, layered layout]{
a --[blue, gluon] b[gluontad=blue, dot] --[blue, gluon] c
};
\end{feynman}
\end{tikzpicture}
\end{document}

Linear and circular coils

1

You'll have more fine control over the shape and type of the coil if you draw the loop manually (see the TikZ documentation for all ways in which you can change the coil):

% !TeX TS-program = lualatex

\documentclass[border=2pt]{standalone}
\usepackage{tikz-feynman}

\begin{document}

\begin{tikzpicture} 
\begin{feynman}
\diagram [inline=(b), horizontal=a to b, layered layout] {
    a -- [blue, gluon] b [dot] b -- [blue, gluon] c};   
\draw[
  blue,
  decorate,
  decoration={
    coil,
    segment length=2.5pt,
    amplitude=2pt,
    post length=1mm,
    pre length=1mm
  },
] (b) arc [start angle=-90, end angle=270, radius=0.3cm];
\end{feynman}
\end{tikzpicture}

\end{document}

enter image description here

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