Statistical limit superior and limit inferior

Abstract

Following the concept of statistical convergence and statistical cluster points of a sequence $x$, we give a definition of statistical limit superior and inferior which yields natural relationships among these ideas: e.g., $x$ is statistically convergent if and only if $\textrm {st}\text {-}\textrm {liminf} x= \textrm {st}\text {-}\textrm {limsup} x$. The statistical core of $x$ is also introduced, for which an analogue of Knopp’s Core Theorem is proved. Also, it is proved that a bounded sequence that is $C_{1}$-summable to its statistical limit superior is statistically convergent.