
\begin{center}
    \begin{tikzpicture}
        \draw node [left] {$\Omega(\theta)$} (0,-2) -- (0,2) ;
        \draw  (0,-2) -- (0.7,-2) node [below] {0.2};
        \draw  (0.7,-2) -- (4,-2) node [below] {$\hat{\rho}_{l}$};
        \draw  (4,-2) -- (4,2) node [right] {$\rho$ = 0.2};
        \draw  (0,2) -- (4,2) ;
        \draw [black,thick] (0,-1.5) parabola bend (0.7,-2) (4,0) ;
    \end{tikzpicture}
\end{center}
