On the divergence of greedy algorithms with respect to Walsh subsystems in $L$

Abstract

In this paper we prove that there exists a function which $f(x)$ belongs to $L^1[0,1]$ such that a greedy algorithm with regard to the Walsh subsystem does not converge to $f(x)$ in $L^1[0,1]$ norm, i.e. the Walsh subsystem $\{W_{n_k}\}$ is not a quasi-greedy basis in its linear span in $L^1$.

appears in Journal of Nonlinear Analysis Series A: Theory, Methods & Applications, 2007