Which all suggests this question, that I've wondered before in any case: Suppose we are given a complex Fourier series of form f(t) = Sum_{-oo < n < oo} c_n exp(nit) (with each c_n in C), defining a function that by abuse of notation we call f: R/(2pi)Z —> C . Then: How can you tell from the coefficients {c_n} when f is one-to-one (i.e., self-avoiding)? —Dan ___________________________________________ P.S. Random thought: Isn't it a bit vexing that if the basis functions are exp(it), then the period is 2pi; and if the period is 1, then the basis functions are {exp(2pi*it)} — always with the obnoxious 2pi in the way. Maybe it would be best if the basis functions were {exp(sqrt(2pi)*it} and so the period would be sqrt(2pi), so at least there's some symmetry.