We wrapped up our conversation about numbers of cycles findable in the Feigenbaum Plot, noting again that for every attracting cycle we find, there is an accompanying “evil twin” repelling cycle. These “evil twin” repelling cycles serve a purpose. As the members of the attracting cycle bifurcate, their patterns branch out further and further. When this pattern of branching reaches one of the values of the repelling cycle – indeed it will reach all members of the repelling cycle simultaneously – the branching stops and the system dissolves into chaos once more. This explains why these spontaneously generating cycles appear in “windows” in the Feigenbaum Plot, with an abrupt end to chaos on the left, and an abrupt resuming of chaos on the right.

We wrapped up today with a recap of the work we’ve done so far, occupying our time exclusively within the Real numbers. The last portion of the course will now branch into the Complex numbers, effectively repeating the analyses we’ve done with iterating functions into the complex plane. Our first stop will be to understand how to represent geometric transformation with operations on complex numbers. We modeled this in class by showing how the repetition of a series of geometric transformations can result in the same “fixed point attracting” behavior as we saw with the real numbers.