Difference between revisions of "Greatest lower bound"

 
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Given a [[subset]] <math>S</math> in some larger [[partially ordered set]] <math>R</math>, a '''greatest lower bound''' or '''infemum''' for <math>S</math> is an [[element]] <math>\displaystyle m \in R</math> such that <math>m \leq s</math> for every <math>s \in S</math> and there is no <math>M > m</math> with this same property.
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Given a [[subset]] <math>S</math> in some larger [[partially ordered set]] <math>R</math>, a '''greatest lower bound''' or '''infimum''' for <math>S</math> is an [[element]] <math>m \in R</math> such that <math>m \leq s</math> for every <math>s \in S</math> and there is no <math>M > m</math> with this same property.
  
 
If the greatest lower bound <math>m</math> of <math>S</math> is an element of <math>S</math>, it is also the [[minimum]] of <math>S</math>.  If <math>m \not\in S</math>, then <math>S</math> has no minimum.
 
If the greatest lower bound <math>m</math> of <math>S</math> is an element of <math>S</math>, it is also the [[minimum]] of <math>S</math>.  If <math>m \not\in S</math>, then <math>S</math> has no minimum.

Latest revision as of 13:55, 5 March 2022

Given a subset $S$ in some larger partially ordered set $R$, a greatest lower bound or infimum for $S$ is an element $m \in R$ such that $m \leq s$ for every $s \in S$ and there is no $M > m$ with this same property.

If the greatest lower bound $m$ of $S$ is an element of $S$, it is also the minimum of $S$. If $m \not\in S$, then $S$ has no minimum.

See also

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