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Difference between revisions of "Transitive relation"

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One of the most important properties of a [[binary relation]]. A relation $R$ on a set $A$ is called transitive if, for any $a,b,c\in A$, the conditions $aRb$ and $bRc$ imply $aRc$. [[Equivalence relation]]s and orderings (cf [[Partially ordered set]]) are examples of transitive relations.
 
  
[[Category:Logic and foundations]]
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One of the most important properties of a [[binary relation]]. A relation $R$ on a set $A$ is called transitive if, for any $a,b,c\in A$, the conditions $aRb$ and $bRc$ imply $aRc$: equivalently if the [[composition]] $R \circ R \subseteq R$. [[Equivalence relation]]s and [[Order (on a set)|orderings]] are examples of transitive relations.  The universal relation, $a R b$ for all $a,b \in A$, the equality relation, $a R b$ for $a=b \in A$ and the empty (nil) relation are transitive.
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The intersection of transitive relations on a set is again transitive.  The ''transitive closure'' $R^*$ of a relation $R$ is the smallest transitive relation containing $R$: equivalently the intersection of all transitive relations containing $R$ (there exists at least one such, the universal relation).  It can be described as $a R^* b$ if there exists a finite chain $a = a_0, a_1, \ldots, a_n = b$ such that for each $i=1,\ldots,n$ we have $a_{i-1} R a_i$.
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====References====
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<table>
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<TR><TD valign="top">[a1]</TD> <TD valign="top">  R. Fraïssé, ''Theory of Relations'', Studies in Logic and the Foundations of Mathematics, Elsevier (2011) ISBN 0080960413</TD></TR>
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<TR><TD valign="top">[a2]</TD> <TD valign="top">  P. R. Halmos, ''Naive Set Theory'', Springer (1960) ISBN 0-387-90092-6</TD></TR>
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<TR><TD valign="top">[a3]</TD> <TD valign="top">  P.M. Cohn, "Universal algebra", Reidel (1981) ISBN 90-277-1213-1 {{MR|0620952}} {{ZBL|0461.08001}}</TD></TR>
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</table>

Revision as of 12:23, 6 February 2021

2020 Mathematics Subject Classification: Primary: 03-XX [MSN][ZBL]

One of the most important properties of a binary relation. A relation $R$ on a set $A$ is called transitive if, for any $a,b,c\in A$, the conditions $aRb$ and $bRc$ imply $aRc$: equivalently if the composition $R \circ R \subseteq R$. Equivalence relations and orderings are examples of transitive relations. The universal relation, $a R b$ for all $a,b \in A$, the equality relation, $a R b$ for $a=b \in A$ and the empty (nil) relation are transitive.

The intersection of transitive relations on a set is again transitive. The transitive closure $R^*$ of a relation $R$ is the smallest transitive relation containing $R$: equivalently the intersection of all transitive relations containing $R$ (there exists at least one such, the universal relation). It can be described as $a R^* b$ if there exists a finite chain $a = a_0, a_1, \ldots, a_n = b$ such that for each $i=1,\ldots,n$ we have $a_{i-1} R a_i$.

References

[a1] R. Fraïssé, Theory of Relations, Studies in Logic and the Foundations of Mathematics, Elsevier (2011) ISBN 0080960413
[a2] P. R. Halmos, Naive Set Theory, Springer (1960) ISBN 0-387-90092-6
[a3] P.M. Cohn, "Universal algebra", Reidel (1981) ISBN 90-277-1213-1 MR0620952 Zbl 0461.08001
How to Cite This Entry:
Transitive relation. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Transitive_relation&oldid=33953
This article was adapted from an original article by T.S. Fofanova (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article