Same as in Fig. 2 but with δα = 0.15. In this case, a temporary pressure maximum develops. The Σ_gas(r) profiles are shown for different epochs in panel a. In panel b, the curves of the pressure gradient dP/dr are displayed at the same epochs as in the upper panel. Some of the curves of the pressure gradient cross the horizontal axis at zero, and therefore a temporary pressure trap forms within the following range of epochs: 1.8 × 10⁴ < t < 7 × 10⁴ yr.