Weak statistical convergence and weak filter convergence for unbounded sequences

For every weakly statistically convergent sequence (x(n)) with increasing norms in a Hilbert space we prove that sup(n) parallel to x(n)parallel to/root n < infinity This estimate is sharp We study analogous problem for sonic other types of weak filter convergence. in particular for the Erdos-Ulam filters, analytical P-filters and F-sigma filters We present also a refinement of the recent Aron-Garcia-Maestre result on weakly dense sequences that tend to infinity in norm (C) 2010 Elsevier Inc. All rights reserved.