Definition:Limit Inferior

Definition

Let $\left \langle {x_n} \right \rangle$ be a bounded sequence in $\R$.

Let $L$ be the set of all real numbers which are the limit of some subsequence of $\left \langle {x_n} \right \rangle$.

From Existence of Maximum and Minimum of Bounded Sequence, $L$ has a minimum.

This minimum is called the lower limit, the limit inferior or just liminf.

It can be denoted:

$\displaystyle \liminf_{n \to \infty} \left({x_n}\right) = \underline l$

It can be defined as:

$\displaystyle \liminf_{n \to \infty} \left({x_n}\right) = \sup\left\{{\inf_{m \ge n} x_m: n \in \N}\right\}$

Also see

• Limit Superior

• Limit Inferior of a Sequence of Sets for an extension of this concept into the field of measure theory.

Sources

• K.G. Binmore: Mathematical Analysis: A Straightforward Approach (1977)... (previous)... (next): $\S 5.13$