May be it's not the right place for this, but I don't know the right definition of a strange attractor. Wikipedia states that "An attractor is informally described as strange if it has non-integer dimension or if the dynamics on it are chaotic." In the Tucker's paper about Lorenz system is written that "an attractor is called strange if for almost all pairs of different points in B( Λf ), their forward orbits eventually separate by at least a constant δ (depending only on Λf )." I feel that this definitions are not equivalent. I also would welcome links to useful literature.



Definition of a strange attractor.
This is a good question. For some reason, terminology in dynamical systems is not standardized at all--and it's interesting to disentangle various definitions. A good book to look at is [Differential equations, dynamical systems, and an introduction to chaos](http://books.google.com/books?id=GNOmchErrMgC). The authors (Hirsch, Smale, Devaney) are at the center of the field, and they point out there's no standard definition of even "attractor"! (Let alone "strange attractor," which they only use once, informally.) 


In my view, definitions based on the shape of an attractor (like the first part of Wikipedia's) are a little odd, since you can have chaotic dynamics on geometrically simple attractors. Think of a map with a circle as an attractor on which the dynamics are like $\theta \mapsto 2\theta$.


The second Wikipedia definition, that the dynamics are chaotic, might imply the Tucker definition--but that in turn depends on your definition of chaos. There's interesting work on how various criteria for "chaos" relate. A good entry point might be ["On Devaney's Definition of Chaos"](http://www.jstor.org/pss/2324899) (Banks et al, American Math. Monthly, 1992).


