文摘
We prove that for an ergodic rotation \(R\) and square integrable function \(f\) on a compact abelian group, the ergodic process \(X=(f\circ R^n)_{n\in {\mathbb {Z}}}\) is uniquely determined by its two-dimensional laws if the same holds for the process \(Y=(h\circ f \circ R^n )_{n\in {\mathbb {Z}}},\) for some real bounded function \(h,\) such that all Fourier-Stieltjes coefficients of \(h\circ f\) are non null. Applied to the one or two dimensional torus, this result gives a large class of such processes, for instance any process given by non constant monotone continuous function, or having a discontinuity at an irrational point, on the unit interval, is in the corresponding class. We also prove that all Fourier coefficients of such a monotone function are non null.