Draw rounded lines with tikz

Question

I have drawn a Feynman diagram by tikz using this script

\documentclass[tikz,border=3.14pt]{standalone}
\usepackage[compat=1.1.0]{tikz-feynman}
\usetikzlibrary{backgrounds,calc}
\usepackage{tikz}
\usetikzlibrary{arrows}
\usetikzlibrary{calc}
\usetikzlibrary{automata}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}

\begin{document}
 \tikzset{>=triangle 45}
\tikzset{  
  every node/.append style={font=\small, inner sep = 1pt},
  every edge/.append style={thick},
  electron/.style={postaction={decorate},
  decoration={markings,mark=at position .55 with {\arrow[]{>}}}},
  }


\begin{tikzpicture}
  \node (center) at (0,0) {$ $};
  \foreach \phi in {1,...,3}{
    \node (c_\phi) at (-360/3 * \phi:1cm) {$ $} ;
  }
   ==========================
  \draw[blue] (c_2) edge[out = 25, in = 90, electron] node[above right = 1pt] {$ $}(c_3);
  \draw[blue] (c_1) edge[out = 155, in = -155, electron] node[below left = 1pt] {$ $}(c_2);
  \draw[blue] (c_3) edge[out = -90, in = -25, electron ] node[above left = 1pt] {$ $}(c_1);
   ==========================
  \foreach \phi in {1,...,3}{
    \node (v_\phi) at (360/3 * \phi:2.5cm) {$ $} ;
  }
   ==========================
  \draw[blue] (v_2) edge[out = -25, in = -90, electron] node[below left = 1pt] {$ $} (v_3);
  \draw[blue] (v_1) edge[out = -155, in = 155, electron] node[below right = 1pt] {$ $}(v_2);
  \draw[blue] (v_3) edge[out = 90, in = 25, electron] node[above right = 1pt] {$ $}(v_1);

  \draw[dashed] (v_2) -- (c_1);
  \draw[dashed] (v_1) -- (c_2);
  \draw[dashed] (v_3) -- (c_3);


\end{tikzpicture}

\end{document}

I would like to have a more rounded electron line such that the whole diagram looks like two circles instead of the drawn rounded triangles. I am very much looking for a solution which does not use circle. Any suggestions on improving the script is very appreciated.

Answer 1

If you don't want to use circle, you may use arc.

\documentclass[tikz]{standalone}

\usetikzlibrary{positioning,arrows}
\usetikzlibrary{decorations.markings}

\begin{document}

\begin{tikzpicture}[
    myedge/.style={thick,draw=black, postaction={decorate},
      decoration={markings,mark=at position .6 with {\arrow[black]{triangle 45}}}},
    myshorten/.style={shorten <= 2pt, shorten >= 2pt}]

  \foreach \phi in {1,2,3}{
    \coordinate (A\phi) at (360/3*\phi:1cm);
    \coordinate (B\phi) at (360/3*\phi:2.5cm);
    \draw[myshorten,myedge] (A\phi) arc ( 360/3*\phi: 360/3*(\phi+1): 1cm);
    \draw[myshorten,myedge] (B\phi) arc ( 360/3*\phi: 360/3*(\phi+1): 2.5cm);
  }

  \draw[dashed] (A1) -- (B1);
  \draw[dashed] (A2) -- (B2);
  \draw[dashed] (A3) -- (B3);

\end{tikzpicture}

\end{document}

gives

The shorten messes a little bit with the arc, but it should be ok.

Answer 2

\documentclass[tikz, border=3.14pt]{standalone}
\usetikzlibrary{calc}
\usepackage{tikz}
\usetikzlibrary{arrows.meta,
                backgrounds,
                calc,
                decorations.markings}

\begin{document}
    \begin{tikzpicture}[
electron/.style = {decoration={markings,
                               mark=at position 0.166 with {\arrow{Triangle}},
                               mark=at position 0.499 with {\arrow{Triangle}},
                               mark=at position 0.834 with {\arrow{Triangle}}},
                  postaction={decorate},
                  blue, thick},
                        ]
\draw[electron] (0,0) circle[radius=12mm];
\draw[electron] (0,0) circle[radius=24mm];
%
\foreach \phi in {1,2,3}
{
    \node [circle, fill=white, inner sep=1pt] (v1\phi) at (360/3 * \phi:12mm) {};
    \node [circle, fill=white, inner sep=1pt] (v2\phi) at (360/3 * \phi:24mm) {};
}
%
\draw[dashed]   (v11) -- (v21)
                (v12) -- (v22)
                (v13) -- (v23);
    \end{tikzpicture}
\end{document}

gives

as you can see, for electron are used two circles with three equal spaced arrow heads. dashed lines are between nodes whit white color, which are placed on circles.

Answer 3

Code golfing : two loops, single \draw.

\documentclass[tikz,border=7pt]{standalone}
\usetikzlibrary{bending}
\begin{document}
  \tikz\foreach\a in {0,1,2}\foreach\r in {1,2}
    \draw[blue,thick,latex-,rotate=\a*120]
      (0:\r) edge[dashed,thin,black,.-] (0:2)
      (59:\r) arc (59:-70:\r) node[pos=.457,fill=white,circle,inner sep=1pt]{};
\end{document}

Answer 4

I personally would bend the arrows and also indicate the vertices by dots.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{arrows.meta,bending,decorations.markings} 
\tikzset{% inspired by https://tex.stackexchange.com/a/316050/121799
    arc arrow/.style args={%
    to pos #1 with length #2}{
    decoration={
        markings,
         mark=at position 0 with {\pgfextra{%
         \pgfmathsetmacro{\tmpArrowTime}{#2/(\pgfdecoratedpathlength)}
         \xdef\tmpArrowTime{\tmpArrowTime}}},
        mark=at position {#1-\tmpArrowTime} with {\coordinate(@1);},
        mark=at position {#1-2*\tmpArrowTime/3} with {\coordinate(@2);},
        mark=at position {#1-\tmpArrowTime/3} with {\coordinate(@3);},
        mark=at position {#1} with {\coordinate(@4);
        \draw[-{Triangle[length=#2,bend]}]       
        (@1) .. controls (@2) and (@3) .. (@4);},
        },
     postaction=decorate,
     },
    my electron/.style={arc arrow={to pos 0.5 with length 3mm}},
    vertex dot/.style={draw,circle,fill,scale=0.4}
}


\begin{document}
\begin{tikzpicture}
  \foreach \angle in {120,240,360}{
    \node[vertex dot,blue] (c_\angle) at (\angle:1cm) {} ;
    \node[vertex dot,blue] (v_\angle) at (\angle:2.5cm) {} ;
    \draw[my electron,blue] (\angle:1cm) arc(\angle:{\angle-120}:1cm);
    \draw[my electron,blue] (\angle:2.5cm) arc(\angle:{\angle+120}:2.5cm);
    \draw[dashed] (c_\angle) -- (v_\angle);
  }
\end{tikzpicture}
\end{document}