612041.fig.002
Figure 2: A description of the geometry in Example 2.8. The set made of the points of the annulus , where , is the union of a closed curve (contained in the part of the annulus between and ) and a small segment . The function vanishes at , and it is negative for and positive for (we have painted with a darker color the part of the annulus, where ). The point is the unique fixed point of since .