On Subsets of the Space of Bounded Sequences

The subspace $c_0$ is not complemented in $ac_0$

“…In [11] it is shown that T A 0 = A 0 despite the fact that for some x ∈ ℓ ∞ one has α(T x) < α(x). For further investigation of α(x) we also refer the reader to [12].…”