A note on the maximal operators of Vilenkin-Nörlund means with non-increasing coefficients
In  we investigated some Vilenkin—Nörlund means with non-increasing coefficients. In particular, it was proved that under some special conditions the maximal operators of such summabily methods are bounded from the Hardy space H1/(1+α) to the space weak-L1/(1+α), (0 < α ≦ 1). In this paper we construct a martingale in the space H1/(1+α), which satisfies the conditions considered in , and so that the maximal operators of these Vilenkin—Nörlund means with non-increasing coefficients are not bounded from the Hardy space H1/(1+α) to the space L1/(1+α). In particular, this shows that the conditions under which the result in  is proved are in a sense sharp. Moreover, as further applications, some well-known and new results are pointed out.
Link to publishers version: 10.1556/012.2016.53.4.1342