Abstract. Let S"f be the nth partial sum of the Vilenkin-Fourier series of f € L1 . For 1 < p < oo , we characterize all weight functions w such that if / € IP{w), S"f converges to / in IP(w). We also determine all weight functions w suchthat {S"} is uniformly of weak type (1,1) with respect to
IntroductionThe Vilenkin-Fourier series is a generalization of the Walsh-Fourier series. While the Walsh functions are characters of the countable direct product of groups of order 2, the Vilenkin system consists of characters of G = F|°^0 ZPi, a direct product of cyclic groups of order p¡, where p, is any integer > 2. In this paper, there is no restriction on the orders {/>,} .Let p be the Haar measure on G normalized by piG) = 1. We identify G with the unit interval (0, 1) in the following manner. Let «io = 1, mk = n,=o Pi' k -1.2,....We associate with each {x¡) £ G, 0 < x¡ < p¡, the point Y,™0Xjm~¿x £ (0, 1). If we disregard the countable set of ^,-rationals, this mapping is one-one, onto and measure-preserving. The characters of G axe the finite products of an orthonormal system {k(x) -exp(2nixk/pk), x = {xk} £ G, k = 0, 1, ... . To enumerate the finite products of {tpk} , we write each nonnegative integer « as a finite sum, « = YlT=oakmk , with 0 < ak < pk, and define Xn = nitLo ßk • ^ne functions {xn} are the characters of G, and they form a complete orthonormal system on G.For /el1, let . n -X Snfix)= / f(t)Yxj(x-t)dp(t), «=1,2,..., Jg j=0be the «th partial sum of the Vilenkin-Fourier series of /. In [10], we showed that for / £ Lp , 1 < p < oo, lim [ \S"fi-fi\pdp = 0.