Profiles of the first adiabatic exponent, Γ₁, and the ratio of the local mixing length to the local radius, l/r, in the envelopes of the canonical TPAGB star (cyan solid line) and the cases with only the effect of the extra heating (red dotted line), rotation (blue dashed line), and the companion’s gravity (green dash-dot line) included at a time between two thermal pulses (t = 3500 yr). The horizontal dark solid line in panel a represents the critical .