
The author obtains a new sufficient condition for an infinite Hankel matrix \((a_{i+ j})_{i, j\geq 0}\) to determine a bounded linear operator on a Hilbert space. One form of this condition is that we can write \(a_ k= \lambda_ k \alpha_ k\), with \(\{\lambda_ k\}\) a decreasing sequence in \(\ell^ 2\) and \(\{\alpha_ k\}\) satisfying, for some constant \(K\), \(\left|\sum^ N_{k= m+ 1} \alpha_ k z^ k\right|\leq K\sqrt{N- M}\) for \(| z|= 1\) and \(N> M\geq 0\). The author remarks that the \textit{W. Rudin} and \textit{J. H. Shapiro} polynomials [Proc. Am. Math. Soc. 10, 855-869 (1959; Zbl 0091.057)] can be used to obtain a sequence \(\{\alpha_ k\}\) satisfying this necessary condition and for which \(\{|\alpha_ k|\}\) does not satisfy the well-known Fefferman condition for boundedness. The author also remarks that the question of necessity for his condition remains open.
Toeplitz operators, Hankel operators, Wiener-Hopf operators, Fefferman condition for boundedness, Rudin-Shapiro polynomials, infinite Hankel matrix
Toeplitz operators, Hankel operators, Wiener-Hopf operators, Fefferman condition for boundedness, Rudin-Shapiro polynomials, infinite Hankel matrix
| selected citations These citations are derived from selected sources. This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 3 | |
| popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Average | |
| influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Average | |
| impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Average |
