%0 Journal Article %T Some applications of W. Rudin's inequality to problems of combinatorial number theory %A I. D. Shkredov %J Mathematics %D 2010 %I arXiv %X In the paper we obtain some new applications of well--known W. Rudin's theorem concerning lacunary series to problems of combinatorial number theory. We generalize a result of M.-C. Chang on L_2 (L)-norm of Fourier coefficients of a set (here L is a dissociated set), and prove a dual version of the theorem. Our main instrument is computing of eigenvalues of some operators. %U http://arxiv.org/abs/1002.1886v1