NEW YORK JOURNAL OF MATHEMATICS, vol.23, pp.1531-1537, 2017 (Journal Indexed in SCI)
The fundamental inequality w (A(n)) <= w(n) (A), (n = 1; 2, ...) for the numerical radius is much studied in the literature. But the inverse inequalities for the numerical radius are not well known. By using Hardy-Hilbert type inequalities, we give inverse numerical radius inequalities for reproducing kernel Hilbert spaces. Also, we obtain inverse power inequalities for the Berezin number of an operator.