If
with
then the number and nature of the fixed points and the intersection of the keep set
with the real axis depends on the value of![]()
has
-
No fixed real points if

-
A single fixed point if

-
Two real fixed points
if
If
then the fixed points are complex so
The coefficients of
are real so the roots are complex conjugates and since there is no intersection with the real axis, the keep set is not connected. Further, the intersection of the keep set with the imaginary axis is also zero, since![]()
If
then
has either 1 or 2 real fixed points so
is non – empty. In fact, if
then
is the interval
If
then
consists of the closed interval
from which a sequence of disjoint, non – empty, open subintervals have been removed. In particular,
Furthermore, there is no intersection of
with the imaginary axis since
so
is outside the interval above and
is not in the keep set.