The numerical radius of a weighted shift operator

In this paper, the point spectrum of the real Hermitian part of a weighted shift operator with weight sequence a_1, a_2, . . . , a_n, 1, 1, . . . is investigated and the numerical radius of the weighted shift operator in terms of the weighted shift matrix with weights a_1, a_2, . . . , a_n is formulated explicitly.

CHAOS IN A CLASS OF NONCONSTANT WEIGHTED SHIFT OPERATORS

In this paper, chaos generated by a class of nonconstant weighted shift operators is studied. First, we prove that for the weighted shift operator Bμ : Σ(X) → Σ(X) defined by Bμ(x0, x1, …) = (μ(0)x1, μ(1)x2, …), where X is a normed linear space (not necessarily complete), weak mix, transitivity (hypercyclity) and Devaney chaos are all equivalent to separability of X and this property is preserved under iterations. Then we get that [Formula: see text] is distributionally chaotic and Li–Yorke sensitive for each positive integer N. Meanwhile, a sufficient condition ensuring that a point is k-scrambled for all integers k > 0 is obtained. By using these results, a simple example is given to show that Corollary 3.3 in [Fu & You, 2009] does not hold. Besides, it is proved that the constructive proof of Theorem 4.3 in [Fu & You, 2009] is not correct.

On t-entropy and variational principle for the spectral radius of weighted shift operators

In this paper we introduce a new functional invariant of discrete time dynamical systems—the so-called t-entropy. The main result is that this t-entropy is the Legendre dual functional to the logarithm of the spectral radius of the weighted shift operator on L1(X,m) generated by the dynamical system. This result is called the variational principle and is similar to the classical variational principle for the topological pressure.