Centered operators
Characterizing Fréchet-Schwartz spaces via power bounded operators
We characterize Köthe echelon spaces (and, more generally, those Fréchet spaces with an unconditional basis) which are Schwartz, in terms of the convergence of the Cesàro means of power bounded operators defined on them. This complements similar known characterizations of reflexive and of Fréchet-Montel spaces with a basis. Every strongly convergent sequence of continuous linear operators on a Fréchet-Schwartz space does so in a special way. We single out this type of "rapid convergence" for a sequence...
Conjugacies between ergodic transformations and their inverses
We study certain symmetries that arise when automorphisms S and T defined on a Lebesgue probability space (X, ℱ, μ) satisfy the equation . In an earlier paper [6] it was shown that this puts certain constraints on the spectrum of T. Here we show that it also forces constraints on the spectrum of . In particular, has to have a multiplicity function which only takes even values on the orthogonal complement of the subspace . For S and T ergodic satisfying this equation further constraints arise,...
Contractive projections on the fixed point set of contractions
Convergence of iterates of linear operators and the Kelisky-Rivlin type theorems
Let X be a Banach space and T ∈ L(X), the space of all bounded linear operators on X. We give a list of necessary and sufficient conditions for the uniform stability of T, that is, for the convergence of the sequence of iterates of T in the uniform topology of L(X). In particular, T is uniformly stable iff for some p ∈ ℕ, the restriction of the pth iterate of T to the range of I-T is a Banach contraction. Our proof is elementary: It uses simple facts from linear algebra, and the Banach Contraction...
Convergence of moving averages of multiparameter superadditive processes.
Convergence rates of ergodic limits for semigroups and cosine functions.
Convex combinations of commuting affine operators
Corrigendum to the paper: “A remark on the weighted averages for superadditive processes”.
Counting and convergence in ergodic theory
Courte démonstration du théorème ergodique sur-additif