佩斯金 (Peskin) 和施罗德 (Schroeder) 的复平面符号？

Question

Peskin 和 Schroeder 的 QFT 文本经常使用下图所示的符号来表示变量的复平面。我不认为这种符号是标准的，而且我在 google 上搜索时找不到实现它的方法。如何在 Tikz 中实现这一点？

编辑：为了澄清问题，我指的是下图中与 $p^0$ 呈直角的那部分（这有名字吗？）。我包含此代码只是为了获得一个最小的工作示例，我并不是说我想要完全相同的轮廓。

我有我想要的轮廓的以下代码：

\documentclass[tikz,crop]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings}


\begin{document}

\begin{tikzpicture}
  [
    decoration={%
      markings,
      mark=at position 2.35619cm with {\arrow[line width=1pt]{>}},
      mark=at position 4.71239cm with {\arrow[line width=1pt]{>}},
      mark=at position 7.06858cm with {\arrow[line width=1pt]{>}},
      mark=at position 10.9248cm with {\arrow[line width=1pt]{>}},
      mark=at position 13.9248cm with {\arrow[line width=1pt]{>}},
    }
  ]
  \draw [help lines,->] (-4,0) -- (4,0) coordinate (xaxis);
  \draw [help lines,->] (0,-4) -- (0,1) coordinate (yaxis);
  \node at (0,-2) {$\times$};
  \node at (0.6,-2) {$-ip^1$};
  \path [draw, line width=0.8pt, postaction=decorate] (3,0) node [above] {$R$} arc (0:-180:3) node [above] {$-R$} -- (3,0); 
\end{tikzpicture}

\end{document}

Answer 1

生成类似于 Peskin 的费曼传播子的积分轮廓图的东西是相当简单的。

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{decorations.markings}
\begin{document}
\begin{tikzpicture}
  [Peskin arrow/.style={postaction={decorate,decoration={%
      markings,
      mark=at position #1 with {\arrow[line width=1pt]{stealth}},}}}
  ]
  \draw [help lines] (-4,0) -- (4,0) coordinate (xaxis);
  \draw [help lines] (0,-1.5) -- (0,1.5) coordinate (yaxis);
  \node (p0) at (6,1) {$p^0$};
  \draw (p0.north west) -- (p0.south west)  -- (p0.south east);
  \draw[line width=0.8pt, Peskin arrow=0.2, Peskin arrow=0.8] 
  (-3.5,-0.8) -- (3.5,0.8); 
  \fill (-2,0) circle(2pt) (2,0) circle(2pt);
\end{tikzpicture}
\end{document}

更新后问题的答案：

\documentclass{article}
\usepackage{tikz}
\tikzset{Peskin/.style={path picture={\draw[#1] (path picture bounding box.north
west) -- (path picture bounding box.south west)
-- (path picture bounding box.south east);}}}
\begin{document}
\tikz{\node[Peskin]{$p^0$};} \tikz{\node[Peskin=blue]{$p^0$};}
\tikz{\node[Peskin=thick]{$p^0$};} \tikz{\node[Peskin={blue,thick}]{$p^0$};}

\dots and here is how Michael may have done it: $\begin{array}{|c}p^0\\
\hline\end{array}$
\end{document}

Answer 2

你是指箭头吗？

\documentclass[tikz,crop]{standalone}
\usepackage{tikz}
\usetikzlibrary{decorations.markings, arrows.meta}

\begin{document}
    \begin{tikzpicture}
    [>=Latex,
    decoration={%
        markings,
        mark=at position 2.35619cm with {\arrow[line width=1pt]{>}},
        mark=at position 4.71239cm with {\arrow[line width=1pt]{>}},
        mark=at position 7.06858cm with {\arrow[line width=1pt]{>}},
        mark=at position 10.9248cm with {\arrow[line width=1pt]{>}},
        mark=at position 13.9248cm with {\arrow[line width=1pt]{>}},
    }
    ]
    \draw [help lines,->] (-4,0) -- (4,0) coordinate (xaxis);
    \draw [help lines,->] (0,-4) -- (0,1) coordinate (yaxis);
    \node at (0,-2) {$\times$};
    \node at (0.6,-2) {$-ip^1$};
    \path [draw, line width=0.8pt, postaction=decorate] (3,0) node [above] {$R$} arc (0:-180:3) node [above] {$-R$} -- (3,0); 
    \end{tikzpicture}
\end{document}