Resumen de Uniform approximation by universal series on arbitrary sets

Vangelis Stefanopoulos

• By considering a tree-like decomposition of an arbitrary set we prove the existence of an associated series with the property that its partial sums approximate uniformly all elements in a relevant space of bounded functions. In a topological setting we show that these sums are dense in the space of continuous functions, hence in turn any Borel measurable function is the almost everywhere limit of an appropriate sequence of partial sums of the same series. The coefficients of the series may be chosen in c0, or in a weighted lp with 1 < p < 8, but not in the corresponding weighted l1.