On Conditionally Universal Functions with respect to the Walsh system

Abstract

This paper proves theorems on the existence of conditionally universal functions and universal triads with respect to the Walsh system defined by the author. The proof method of these theorems provides a new approach to constructing universal series in the Walsh system: by varying its values on a certain set of arbitrarily small measure, any measurable almost everywhere finite function can be turned into a function such that, after choosing the corresponding signs for the terms of the Fourier-Walsh series of the changed function, we can achieve the fact that the obtained series is universal in the class of all measurable functions.