Distinguishing smooth functions by a finite number of point values, and a version of the Takens embedding theorem

Abstract

We prove a general result showing that a finite-dimensional collection of smooth functions whose differences cannot vanish to infinite order can be distinguished by their values at a finite collection of points; this theorem is then applied to the global attractors of various dissipative parabolic partial differential equations. In particular for the one-dimensional complex Ginzburg–Landau equation and for the Kuramoto–Sivashinsky equation, we show that a finite number of measurements at a very small number of points (two and four, respectively) serve to distinguish between different elements of the attractor: this gives an infinite-dimensional version of the Takens time-delay embedding theorem.