THE TAKENS EMBEDDING THEOREM

In his paper [Takens, 1981] on strange attractors and turbulence, Floris Takens proves a theorem giving conditions under which a discrete-time dynamical system can be reconstructed from scalar-valued partial measurements of internal states. We discuss Takens' theorem in terms suitable for a general audience, and give an alternative and more detailed proof of this important result, making use of two basic facts. The first is the Whitney embedding theorem, which we use in an alternative to Takens' original argument away from periodic points of small periods. Near the periodic points we adapt a proof that typical scalar-output linear time-invariant control systems are completely observable.