Summary: Szemerédi’s theorem [E. Szemerédi, Acta Arith. 27, 199–245 (1975; Zbl 0303.10056)] states that a set of integers with positive upper density contains arbitrarily long arithmetic progressions. V. Bergelson and A. Leibman [J. Am. Math. Soc. 9, 725–753 (1996; Zbl 0870.11015)] generalized this, showing that sets of integers with positive upper density contain arbitrarily long polynomial configurations; Szemerédi’s theorem corresponds to the linear case of the polynomial theorem. We focus on the case farthest from the linear case, that of rationally independent polynomials. We derive results in ergodic theory and in combinatorics for rationally independent polynomials, showing that their behavior differs sharply from the general situation.