Help to draw a simple Dynkin diagram either with dynkin-diagrams or tikz

I have some troubles drawing a Dynkin diagram as I want to. I produced the following code. But it does not do what I want to do.

\begin{dynkinDiagram}[edge length=2cm, edge/.style={ultra thick}, root radius=.2cm]{A}{o.ooo}
\node[below=.2cm] at (root 3) {$\beta\perp\alpha+\gamma$};
\node[below=.2cm] at (root 4) {$\gamma$};
\end{dynkinDiagram}


I list some problems: (1) The circles around the nodes are not ultra thick. (2) The dashed line between (root 1) and (root 2) is not ultra thick either. (3) The labels at (root 3) and (root 4) are not horizontally aligned. (4) I want to produce a brace over (root 1) to (root 2) (labelled $\alpha'$) as well as a brace over (root 1) to (root 3) (labelled $\alpha$), and I tried \dynkinBrace or \dynkinBrace* for it which produced a fatal error and stopped compiling.

I would be happy to use tikz instead of the package dynkin-diagrams. But with tikz, I am even more lost. I cannot produce code there which explains the idea.

In the end, I want to center the picture and wrap it in a figure environment. I am not sure, if that can be done with the \begin{dynkinDiagram}...\end{dynkinDiagram} code sample. As you see from the miniature size the package dynkin-diagrams produces, these diagrams are supposed to be used inline. But I want a real figure here.

Thank you!

Like this?

\documentclass[tikz,border=5mm]{standalone}
\usetikzlibrary{decorations.pathreplacing}
\begin{document}
\begin{tikzpicture}[ultra thick]
\def\a{1}
\tikzset{dynkin/.style={circle,draw,minimum size=2mm}}
\path
(0,0)      node[dynkin] (N1) {}
++(0:\a)   coordinate (A) ++(0:\a) coordinate (B)
++(0:\a)   node[dynkin] (N2) {}
++(0:2*\a) node[dynkin] (N3) {} +(-90:.5) node{$\beta\perp\alpha+\gamma$}
++(0:2*\a) node[dynkin] (N4) {} +(-90:.5) node{$\gamma$};

\draw[dashed] (A)--(B);
\draw (N1)--(A) (B)--(N2)--(N3)--(N4);
\draw[decorate,decoration={brace,raise=5mm},blue,thick]
(N2.center)--(N1.center) node[midway,below=6mm]{$\alpha'$};
\draw[decorate,decoration={brace,raise=5mm},blue,thick]
(N1.center)--(N3.center) node[midway,above=6mm]{$\alpha$};
\end{tikzpicture}
\end{document}

• Thank you so much! It is exactly what I wanted to achieve. I will study your code and hope I can learn to do it myself in the future. I will acknowledge your contribution. Aug 4 '19 at 17:43

To compare your code with mine:

\documentclass{amsart}
\usepackage{dynkin-diagrams}
\begin{document}
\begin{dynkinDiagram}[edge length=2cm, edge/.style={ultra thick}, root radius=.2cm]{A}{o.ooo}
\node[below=.2cm] at (root 3) {$\beta\perp\alpha+\gamma$};
\node[below=.2cm] at (root 4) {$\gamma$};
\end{dynkinDiagram}

\begin{dynkinDiagram}[indefinite edge/.style={ultra thick,densely dashed},o/.style={ultra thick,fill=white,draw=black},edge length=2cm, edge/.style={ultra thick}, root radius=.2cm]{A}{o.ooo}
\node[below=.2cm] at (root 3) {$\beta\perp\alpha+\gamma$};
\node[below=.2cm] at (root 4) {$\gamma$};
\dynkinBrace*[\alpha]{1}{3}
\dynkinBrace[\alpha']{1}{2}
\end{dynkinDiagram}
\end{document}

• Thank you! For this problem, I prefer the appearance of the tikz solution. For other problems, the cramped style may be more suitable. The corresponding code for dynkin-diagrams will be certainly useful. Aug 18 '19 at 18:39