Φ versus δ

The left panel plots $Φ$ as a function of $δ$⁠, and the right panel plots the first-order partial derivatives of $Φ$ w.r.t. $δ$⁠. Four lines for $ω¯=1,0.75,0.5$⁠, and 0.25 are plotted. The numerical values for the plots are shown in the subtitles.