Invariant and Absolute Invariant Means of Double Sequences

SEMIGROUP ACTIONS , WEAK ALMOST PERIODICITY, AND INVARIANT MEANS

Let S be a topological semigroup acting on a topological space X. We develop the theory of (weakly) almost periodic functions on X, with respect to S, and form the (weakly) almost periodic compactifications of X and S, with respect to each other. We then consider the notion of an action of Son a Banach space, and on its dual, and after defining S-invariant means for such a space, we give a...

Absolute Torsion and Eta-invariant

In a recent joint work with V. Turaev [6], we defined a new concept of combinatorial torsion which we called absolute torsion. Compared with the classical Reidemeister torsion, it has the advantage of having a well-determined sign. Also, the absolute torsion is defined for arbitrary orientable flat vector bundles, and not only for unimodular ones, as is classical Reidemeister torsion. In this p...

Some New Double Sequence Spaces of Invariant Means

First, we recall some notations and definitions which will be used throughout the paper (cf. [12]). A double sequence x = (xjk) of real or complex numbers is said to be bounded if ‖x‖∞ = supj,k |xjk| < ∞. We denote the space of all bounded double sequences by L. A double sequence x = (xjk) is said to converge to the limit L in Pringsheims sense (shortly, p-convergent to L) if for every ε > 0 th...

Substitution Invariant Beatty Sequences

with θ irrational and taken to satisfy 0 < θ < 1; plainly this may be assumed without loss of generality. Evidently (fn) is a sequence of zeros and ones. Denote by w0 and w1 words on the alphabet {0, 1} ; that is, finite strings in the letters 0 and 1. Then the sequence (fn) is said to be invariant under the substitution W given by W : 0 −→ w0, 1 −→ w1, if the infinite strings fθ = f1f2f3 . . ....

Substitution invariant cutting sequences