1

I apologize in advance if this question (or one which implies an answer to this) has already been asked. Any suggestions on how to draw in Latex a diagram of the following shape ?

enter image description here

Thank you very much !

3

There are countless possibilities to do that. I hope this gives you something to build on.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{positioning}
\begin{document}
\begin{tikzpicture}[bullet/.style={circle,fill,inner sep=2pt}]
 \foreach \X in {1,2,3}
 {\node[bullet,label=above:$\Sigma_\X^0$] (S\X) at (3*\X,1){};
 \node[bullet,label=below:$\Pi_\X^0$] (P\X) at (3*\X,-1){};
 }
 \node[bullet,left=1.5cm of S1,label=above:$\{2^\omega\}$] (w){};
 \node[bullet,left=1.5cm of P1,label=below:$\{\emptyset\}$] (e){};
 \path (w) --(P1) node[midway,bullet,label=above:$\Delta^0_1$]{};
 \foreach \X [count=\Y] in {2,3}
 {\path (S\X) -- (P\Y) node[midway,font=\Large\bfseries,
  label=above:{$\omega_1\ifnum\X=3
  ^{\omega_1}
  \fi$ alternations}]{\dots};}
\end{tikzpicture}
\end{document}

enter image description here

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