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Difference between revisions of "Compact lattice element"

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An element $a$ of a lattice $L$ for which the condition
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An element $a$ of a [[complete lattice]] $L$ for which the condition
 
$$
 
$$
 
a \le \bigvee_{j \in J} x_j\,,\ \ x_j \in L\,,
 
a \le \bigvee_{j \in J} x_j\,,\ \ x_j \in L\,,
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$$
 
$$
 
for some finite subset $\{j_1,\ldots,j_k\} \subset J$.
 
for some finite subset $\{j_1,\ldots,j_k\} \subset J$.
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An [[algebraic lattice]] is one in which each element is the union (least upper bound) of a set of compact elements. 
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A '''finite''' element $b$ of a lattice $L$ is one for which the condition
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$$
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b \le \bigvee_{d \in D} d
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$$
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for a [[directed set]] $D \subset L$ implies
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$$
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b \le d
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$$
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for some $d \in D$.
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In a complete lattice, the compact elements are precisely the finite elements.
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====References====
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<table>
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<TR><TD valign="top">[1]</TD> <TD valign="top">  B. A. Davey, H. A. Priestley, ''Introduction to lattices and order'', 2nd ed. Cambridge University Press  (2002) {{ISBN|978-0-521-78451-1}}</TD></TR>
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</table>

Latest revision as of 08:06, 26 November 2023

2020 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=36183
This article was adapted from an original article by T.S. Fofanova (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article