# Compact lattice element

From Encyclopedia of Mathematics

2010 Mathematics Subject Classification: *Primary:* 06B23 [MSN][ZBL]

An element $a$ of a complete lattice $L$ for which the condition $$ a \le \bigvee_{j \in J} x_j\,,\ \ x_j \in L\,, $$ implies $$ a \le x_{j_1} \vee \cdots \vee x_{j_k} $$ for some finite subset $\{j_1,\ldots,j_k\} \subset J$.

An algebraic lattice is one in which each element is the union (least upper bound) of a set of compact elements.

A **finite** element $b$ of a lattice $L$ is one for which the condition
$$
b \le \bigvee_{d \in D} d
$$
for a directed set $D \subset L$ implies
$$
b \le d
$$
for some $d \in D$.

In a complete lattice, the compact elements are precisely the finite elements.

#### References

[1] | B. A. Davey, H. A. Priestley, Introduction to lattices and order, 2nd ed. Cambridge University Press (2002) ISBN 978-0-521-78451-1 |

**How to Cite This Entry:**

Compact lattice element.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Compact_lattice_element&oldid=36188

This article was adapted from an original article by T.S. Fofanova (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article