Examples of b ( a ) curves belonging to the class U 0/ TM. Examples of b(a) curves belonging to the class U 0/TM, as described by Eq. (15). We have assumed for all the plots ω = 2, A1 = 1 and Ψ1 = 0. As predicted by Eq. (16), in the case M = 1 we obtain an ellipse with a ratio ω between the two semi-axes. Examples of the M = 2 case are shown in the plots (b), (c), (d) and (e), for different choices of the parameters A2 and Ψ2. As expected, three ellipses appear in the case U 0/T 3 (plot f).