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I produced this Feynman graph : 

\documentclass[a4paper]{article}
\usepackage{feynmp-auto}

\begin{document}

\begin{fmffile}{loop}
\begin{equation}
\begin{fmfgraph*}(70,50)
\fmfleft{q1}
\fmfright{q4}
\fmftop{q2,q3}
\fmflabel{$\infty$}{q1}
\fmflabel{$1$}{q2}
\fmflabel{$z$}{q3}
\fmflabel{$0$}{q4}
\fmf{plain}{v1,q2}
\fmf{plain}{v2,q3}
\fmf{plain}{v2,q4}
\fmf{plain}{v1,q1}
\fmf{plain,label=$q$}{v1,v2}
\end{fmfgraph*}
\end{equation}
\end{fmffile}  

\end{document}

which gives enter image description here

but I want the $\infty$ and 0 lines to be horizontal, and the 1 and z lines to be vertical. How can I do this ?

Julien Roussillon
  • 309
  • My knowledge of Feynman graphs seems to have declined over the years, but what does this graph show? –  Jun 28 '15 at 21:52
  • These two representations have the same meaning, I'm using it in CFT and they are a part of correlation functions. But when we work with the vertex operators formalism, the second representation seems more natural. – Julien Roussillon Jun 28 '15 at 22:22

1 Answers1

3

Based on the answer of Gonzalo Medina, I have tried to create a Feynman diagram as you wished. I am not sure if I got you right? But as far as I know you asked for a Feynmandiagram with two horizontal and two vertical lines?

\documentclass[11pt]{standalone}
\usepackage{tikz}
\usetikzlibrary{positioning,arrows}
\usetikzlibrary{decorations.pathmorphing}
\usetikzlibrary{decorations.markings}

\begin{document}

\tikzset{
line/.style={thick, decorate, draw=black,}
 }

\begin{tikzpicture}[node distance=1cm and 1.5cm]
\coordinate[label=above:1] (e1);
\coordinate[below=of e1] (aux1);
\coordinate[left=of aux1,label=left:$\infty$] (e2);
\coordinate[right=3cm of aux1] (aux2);
\coordinate[above=of aux2,label=above:z] (e3);
\coordinate[right=of aux2,label=right:0] (e4);

\draw[line] (e1) -- (aux1);
\draw[line] (aux1) -- (e2);
\draw[line] (e3) -- (aux2);
\draw[line] (aux2) -- (e4);
\draw[line] (aux1) -- node[label=below:q] {} (aux2);
\end{tikzpicture}
\end{document}

Feynman

Hopefully I got your question right?

Community
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Amelie B. Blackstone
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    Yes, it seems to be what the O.P. wants to have, but it's a strange graph in my point of view –  Jun 28 '15 at 21:57
  • 2
    Thank you for your help, I needed this graph. Yes it's a strange graph, but I'm working with conformal blocks in conformal field theory, and this representation is more convenient to me. Thanks again! – Julien Roussillon Jun 28 '15 at 22:17
  • @JulienRoussillon My pleasure. As Herr Hupfer pointed it out it is a weird Feynman diagram. But if it was what you needed, all is fine ;-) ... I think the easiest way to make Feynman diagrams are by using Tikz. Especially the answer of Medina is really good to use. He has definded the style of gluons and particles as well ;-) – Amelie B. Blackstone Jun 28 '15 at 22:25