Proper circle by merging four fermionic propagators in a Feynman diagram

Question

I want to make the loop in the following feynman diagram look like a proper circle

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage[compat=1.1.0]{tikz-feynman}
%Compiled using LuaLatex%
\begin{document}

\begin{center}
\feynmandiagram[horizontal=a to c]{
i1[particle =\(\phi_{0}\)] --[fermion, insertion=0.0] a, 
a --[fermion, insertion=0.99, quarter right] b --[anti fermion, quarter right] c --[fermion, insertion=0.99, quarter right] d --[anti fermion, quarter right] a,
i2[particle =\(\delta \bar{\phi}(k)\)] --[fermion] a,
c --[anti fermion, insertion=0.99] f1[particle =\(\phi_{0}\)],
c --[anti fermion] f2[particle =\(\delta \bar{\phi}(k)\)],
};
\end{center}

\end{document}

Can anyone help me with this?

score 1 · Accepted Answer · answered Dec 03 '18 at 14:34

Unfortunately, using the graph drawing library became more difficult recently because of this issue, which could be resolved. Even more, it became a bit random because of this unresolved issue. However, on the bright side, if you do not use graph drawing, it is really easy to draw the diagram with a spotless circle.

\documentclass{article}
\usepackage{tikz-feynman}
\makeatletter
\tikzset{my insertion/.style={
    /tikz/decoration={
      markings,
      mark=at position #1 with {
        \draw [\tikzfeynman@insertion@style] (-\tikzfeynman@insertion@size, -\tikzfeynman@insertion@size) -- (\tikzfeynman@insertion@size, \tikzfeynman@insertion@size);
        \draw [\tikzfeynman@insertion@style] (-\tikzfeynman@insertion@size, \tikzfeynman@insertion@size) -- (\tikzfeynman@insertion@size, -\tikzfeynman@insertion@size);
      },
    }}}
\makeatother
\begin{document}
\begin{tikzpicture}
\draw[postaction={/tikzfeynman/with arrow=0.25,
/tikzfeynman/with reversed arrow=0.75}] (0,0) node[above left]{\(\delta \bar{\phi}(k)\)}
-- ++ (1,-1) coordinate(v1) -- ++(-1,-1) node[below left]{\(\phi_{0}\)};
\draw[postaction={/tikzfeynman/with arrow=0.125,
my insertion=0.25,
/tikzfeynman/with reversed arrow=0.375,
/tikzfeynman/with arrow=0.625,
my insertion=0.75,
/tikzfeynman/with reversed arrow=0.875,}] (v1) arc(-180:180:1.5)
coordinate[midway] (v2);
\draw[postaction={/tikzfeynman/with reversed arrow=0.5}] (v2) -- ++ (1,1)
node[above right]{\(\delta \bar{\phi}(k)\)};
\draw[postaction={/tikzfeynman/with reversed arrow=0.5}] (v2) -- ++ (1,-1)
node[below right]{\(\phi_{0}\)};
\end{tikzpicture}
\end{document}

Proper circle by merging four fermionic propagators in a Feynman diagram

1 Answers1