# creating particular graph using tikz

I used in the past tikz package to create graph as markov's chain or network nodes but now I would create for my thesis this graph:

I don't know how to recreate in latex, using tikz package, that type of arc.

-
Have you looked at the manual? there are a lot of examples that could be adapted pretty easily for this type of picture. It would probably be best to have a go, and then post what you have so far, highlighting the particular part that is causing you problems :) – cmhughes Nov 25 '12 at 21:48
Well I know to to create the two arcs but I don't know to recreate the arc in the middle...I didn't find anything in the manual – Mazzy Nov 25 '12 at 21:54

One possibility:

\documentclass{article}
\usepackage{tikz}

\begin{document}

\begin{tikzpicture}[circ/.style={draw,circle,minimum size=20pt}]
\node[circ] at (60:2) (S1) {$s_1$};
\node[circ] at (180:2) (1) {$1$};
\node[circ] at (300:2) (S2) {$s_2$};

\path (0,0) edge [->] (S1)
edge [->] (S2)
edge node[auto,swap,xshift=7pt] {$b_1\oplus b_2$} (1);
\draw[->] (S1) -- node[auto,swap] {$b_1$} (1);
\draw[->] (S2) -- node[auto] {$b_2$} (1);
\end{tikzpicture}

\end{document}


-