Existence of double Walsh series universal in weighted $L_μ^1[0,1]^2$ spaces (1501.00829v1)

Abstract: In this paper we consider a question on existence of double Walsh series universal in weighted $L_\mu^1[0,1]^2$ spaces. We construct a weighted function $\mu(x,y)$ and a series by double Walsh system of the form $$\sum_{n,k=1}^\infty c_{n,k}W_n(x)W_k(y)\ \ \mbox{with} \ \ \sum_{n,k=1}^\infty \left | c_{n,k} \right|^q <\infty\ \mbox{for all}\ q>2,$$ which is universal in $L_\mu^1[0,1]^2$ concerning subseries with respect to convergence, in the sense of both spherical and rectangular partial sums.