Archive for February, 2010

Reading “Complex A Guided Tour”

Saturday, February 13th, 2010

This is a fascinated book by Melanie Mitchell. This book caught my attention when I was reading a paper by Dr. Jie Liang. Complexity is a very research topic/discipline. In my view it is somewhat the opposite of reductionist’s approach to phenomena in nature. From the complexity point of view, the underlying rules of brains, insect colonies, cells, economy, are very simple. It is the question of how that is complicate. I heard people cited Philip Anderson, a Novel Lauret in Physics said “More is different.” In Physics, after college or graduate school, one could solve a one electron or hydrogen molecule system pretty comfortably. But anything beyond that could be very murky, lots of approximation and assumptions will be needed. Although we know the simple rules still hold. But a Hamilton with many interactions is just too hard to solve.

So Mitchell’s book is really about the complexity and she uses lots of biology problems to illustrate the solution from complexity. I’m still reading first chapters, but I’d like to rephrase parts of what I read so far.

One example is the ant colony. One ant is very simple, it eats, moves, and that is pretty much all. But when lots of ants meet, they form an intelligence like creator, they know where to move, how to move, and do everything coherently. Look deep you see, each still perform its relatively simple actions, but as a whole, they build themselves into a complex structure performing important survival functions like, use soil, leaves, and twigs to construct nests… The immediate analogy is the brain. There are billions of neurons(ants) in the brain and each performing simple actions, fire and receiving impulses. But as a whole, it has emotions, consciousness,…

There are some common properties of complex systems. They all have complex collective behavior. They do signaling and information processing. And the last, they adapt to various eviromental stresses through learning or evolutionary processes. So she prosed a definition for complexity:

Complex system is a system in which large networks of components with no central control and simple rules of operarion give rise to complex collective behavior, sophisticated information processing, and adaptation via learning or evolution.

The book can be found on Amazon.