Definition:Infimum of Real Sequence
This page is about Infimum of Real Sequence. For other uses, see Infimum.
Definition
Let $\sequence {x_n}$ be a real sequence.
Let $\set {x_n: n \in \N}$ admit an infimum.
Then the infimum of $\sequence {x_n}$) is defined as:
- $\map \inf {\sequence {x_n} } = \map \inf {\set {x_n: n \in \N} }$
Also known as
Particularly in the field of analysis, the infimum of a set $T$ is often referred to as the greatest lower bound of $T$ and denoted $\map {\mathrm {glb} } T$ or $\map {\mathrm {g.l.b.} } T$.
Some sources refer to the infimum of a set as the infimum on a set.
Some sources refer to the infimum of a set as the meet of the set and use the notation $\bigwedge T$ or $\ds \bigwedge_{y \mathop \in T} y$.
Some sources introduce the notation $\ds \inf_{y \mathop \in T} y$, which may improve clarity in some circumstances.
Some older sources, applying the concept to a (strictly) decreasing real sequence, refer to an infimum as a lower limit.
Also defined as
Some sources refer to the infimum as being the lower bound.
Using this convention, any element less than this is not considered to be a lower bound.
Linguistic Note
The plural of infimum is infima, although the (incorrect) form infimums can occasionally be found if you look hard enough.