答案1
提醒一句:我不太了解tikz-feynman
(或者说根本不了解费曼图),所以可能有更好的方法来绘制这些。在这种情况下,粗线本身tikz-feynman
根本不是用 TikZ 绘制的。但作为一个快速而粗略的例子:
\documentclass{article}
\usepackage{tikz-feynman}
\begin{document}
\begin{tikzpicture}
\begin{feynman}
\vertex (a) ;
\vertex [below right=of a] (b) ;
\vertex [above right=of b] (c) ;
\diagram* { (a) -- [fermion] (b) -- [fermion] (c)};
\end{feynman}
% adjust the line width as desired
\draw [line width=1mm] (a|-b) -- node[below=5mm,font=\huge] {$R_1$} (b-|c);
\end{tikzpicture}
\begin{tikzpicture}
\begin{feynman}
\vertex (a1) ;
\vertex [below right=of a] (b1) ;
\vertex [above right=of b] (c1) ;
\vertex [right=4mm of c1] (a2) ;
\vertex [below right=of a2] (b2) ;
\vertex [above right=of b2] (c2) ;
\diagram* {
(a1) -- [fermion] (b1) -- [fermion] (c1),
(a2) -- [fermion] (b2) -- [fermion] (c2)
};
\end{feynman}
\draw [line width=1mm] (b1) -- node[below=5mm,font=\huge] {$R_2$} (b2);
\end{tikzpicture}
\end{document}