使用 feynman-tikz 绘制 u 通道图

Question

我想创建一个类似于下图的费曼图：

但是，我不太清楚这个过程。我特别感兴趣的是捕捉图表的结构，而不是箭头样式。您能提供如何实现这一点的指导吗？

我尝试过改变这个，但是失败了：

\begin{tikzpicture}
    \begin{feynman}
    \diagram [vertical'=a to b] {
         i1
              -- [scalar] a [small, dot]
              -- [draw=none] f1 ,
          a -- [scalar] b [small, dot,],
          i2
              -- [draw=none] b
              -- [scalar] f2,
          };
    \diagram* {
          (i2) -- [scalar] (a),
          (f1) -- [scalar] (b),
           };
    \end{feynman}
\end{tikzpicture}

生成结果：

Answer 1

这是一种从头开始执行的方法，无需任何 feynman 包。

主要步骤：

1. 确定坐标（将你的截图保存为udiag.png）
2. 通过第一个简单的绘图检查并调整坐标
3. 绘制所有连接，包括圆弧
4. 在后续动作中使用装饰标记来放置箭头

如果愿意，您可以编写更密集的代码。但是，我更喜欢让它易于理解……这对于初学者来说已经有点难以理解了tikz。

\documentclass[10pt,border=3mm,tikz]{standalone}% 1 page per tikzpicture
\usepackage{graphicx}%              to include the sketch
\usepackage{tikz}%                  Tikz
\usetikzlibrary{arrows.meta,%       for arrow shapes
                decorations.markings}% to position arrows on path

\begin{document}
 % ~~~ let's identify coordinates ~~~
 \tikz{
    \node {\includegraphics{udiag}};
    \draw (-5,-4) grid (5,5);
 }

 % ~~~ test the coordinates ~~~~~~~
 \tikz{
    \coordinate (A) at (0,0);
    \coordinate (B) at (3,4);
    \coordinate (C) at (10,8);
    \coordinate (D) at (10,0);
    \coordinate (E) at (7,4);
    \coordinate (F) at (0,8);
    
    \draw (A) node{A} -- (B)node{B} -- (C)node{C};
    \draw (D)node{D} -- (E)node{E} -- (F)node{F};
 }

 % ~~~ let's do some more ~~~~~~~
 \tikz[
        dash pattern=on 6mm off 4.1mm,% adjusted dash pattern
        line width=2pt,%                adjusted linewidth
    ]{
    \coordinate (A) at (0,0);
    \coordinate (B) at (3,4);
    \coordinate (C) at (10,8);
    \coordinate (D) at (10,0);
    \coordinate (E) at (7,4);
    \coordinate (F) at (0,8);
    
    % ~~~ lines, semi circle and dots ~~~~~~~~~~~~~~~~
    \draw (A) -- (B) -- (C);
    \draw (D) -- (E) -- (F);
    \draw (B) -- (E) arc[start angle=0, end angle=-180,radius=2];
    % ~~~ overwriting the dash pattern defined above for the circles ~~~
    \draw[fill=black,solid]  (B) circle[radius=2.5mm] 
                             (E) circle[radius=2.5mm];
 }

 % ~~~ finalizing with markings and postactions ~~~~~~~
 \tikz[
        dash pattern=on 6mm off 4.1mm,% adjusted dash pattern
        line width=2pt,%                adjusted linewidth
        decoration={
            markings,
            mark=at position .25 with {\arrow{Triangle[length=1cm]}} , 
            mark=at position .75 with {\arrow{Triangle[length=1cm]}} , 
        }
    ]{
    \coordinate (A) at (0,0);
    \coordinate (B) at (3,4);
    \coordinate (C) at (10,8);
    \coordinate (D) at (10,0);
    \coordinate (E) at (7,4);
    \coordinate (F) at (0,8);
    
    % ~~~ lines, semi circle and dots; arrows-decoration ~~~~~~~~~~~~~~~~
    \draw[postaction={decorate}] (A) --  (B) -- (C);
    \draw[postaction={decorate}] (D) -- (E) -- (F);
    \draw (B) -- (E) arc[start angle=0, end angle=-180,radius=2];
    % ~~~ overwriting the dash pattern defined above for the circles ~~~
    \draw[fill=black,solid]  (B) circle[radius=2.5mm] 
                             (E) circle[radius=2.5mm];
 }

\end{document}