Matrix Summability in Amenable Semigroups

Subsemigroups of Cancellative Amenable Semigroups

We generalize a theorem of Frey by giving sufficient conditions for a subsemigroup T of a cancellative left amenable semigroup S to be left amenable. In particular, we show that if S is left amenable and T does not contain a free subsemigroup on two generators, then T is left amenable as well.

A CHARACTERIZATION OF EXTREMELY AMENABLE SEMIGROUPS

Let S be a discrete semigroup, m (S) the space of all bounded real functions on S with the usualsupremum norm. Let Acm (S) be a uniformly closed left invariant subalgebra of m (S) with 1 c A. We say that A is extremely left amenable if there isamultiplicative left invariant meanon A. Let P = {h ?A: h =|g-1,g | forsome g ?A, s ?S}. It isshown that . A is extremely left amenable if and only ...

Matrix Summability in 7"-fields

when un = 22"-o a-inUi for all ra^O. If the sequence to sequence transformation associated with A is such that [u/[ ] exists and converges whenever [un] converges we call A a K matrix. If [uJ ] exists and converges to limn,,, un whenever this limit exists we call A a T matrix. Similar names for the series to sequence and the series to series matrices are TCi, 7\ and K2, T2 matrices respectively...

Absolute matrix summability methods

On absolute matrix summability methods