The T_c-Σ plane at r = 20M for a nonrotating BH (a_∗ = 0). The dotted lines connect solutions for the vertical structure of slim disks that have the same value of the advection parameter f^adv. The locus of standard (radiatively efficient, f^adv = 0) disk solutions is shown with the thick dotted line. The solid thick line represents the vertical slim-disk solutions for different accretion rates (indicated by triangles), and the dashed line presents corresponding solutions of the conventional polytropic slim-disk model (see Sect. 5). The difference between the two lines in the low Ṁ limit corresponds to the difference in Σ between the two models (see Fig. 17).