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Difference between revisions of "Separable semi-group"

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A [[Semi-group|semi-group]] in which <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845001.png" /> for elements <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845002.png" />, <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845003.png" /> implies that <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845004.png" />. If a semi-group <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845005.png" /> has a partition into sub-semi-groups that satisfy the cancellation law, then <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845006.png" /> is separable. For commutative semi-groups the converse holds; moreover, any commutative separable semi-group can be expanded into a [[Band of semi-groups|band of semi-groups]] (trivially into a semi-lattice) with the cancellation law. A commutative semi-group is separable if and only if it can be imbedded in a [[Clifford semi-group|Clifford semi-group]]. A periodic semi-group is separable if and only if it is a Clifford semi-group. A commutative semi-group <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845007.png" /> is separable if and only if its characters separate the elements of <img align="absmiddle" border="0" src="https://www.encyclopediaofmath.org/legacyimages/s/s084/s084500/s0845008.png" />.
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A [[Semi-group|semi-group]] in which $x^2=xy=y^2$ for elements $x$, $y$ implies that $x=y$. If a semi-group $S$ has a partition into sub-semi-groups that satisfy the [[cancellation law]], then $S$ is separable. For commutative semi-groups the converse holds; moreover, any commutative separable semi-group can be expanded into a [[Band of semi-groups|band of semi-groups]] (trivially into a semi-lattice) with the cancellation law. A commutative semi-group is separable if and only if it can be imbedded in a [[Clifford semi-group]]. A periodic semi-group is separable if and only if it is a Clifford semi-group. A commutative semi-group $S$ is separable if and only if its characters separate the elements of $S$.
  
 
====References====
 
====References====
<table><TR><TD valign="top">[1]</TD> <TD valign="top">  A.H. Clifford,  G.B. Preston,  "The algebraic theory of semigroups" , '''1''' , Amer. Math. Soc.  (1961)</TD></TR></table>
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<table><TR><TD valign="top">[1]</TD> <TD valign="top">  A.H. Clifford,  G.B. Preston,  "The algebraic theory of semigroups" , '''1''' , Amer. Math. Soc.  (1961) {{ZBL|0111.03403}}</TD></TR></table>

Latest revision as of 17:58, 22 December 2023

A semi-group in which $x^2=xy=y^2$ for elements $x$, $y$ implies that $x=y$. If a semi-group $S$ has a partition into sub-semi-groups that satisfy the cancellation law, then $S$ is separable. For commutative semi-groups the converse holds; moreover, any commutative separable semi-group can be expanded into a band of semi-groups (trivially into a semi-lattice) with the cancellation law. A commutative semi-group is separable if and only if it can be imbedded in a Clifford semi-group. A periodic semi-group is separable if and only if it is a Clifford semi-group. A commutative semi-group $S$ is separable if and only if its characters separate the elements of $S$.

References

[1] A.H. Clifford, G.B. Preston, "The algebraic theory of semigroups" , 1 , Amer. Math. Soc. (1961) Zbl 0111.03403
How to Cite This Entry:
Separable semi-group. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Separable_semi-group&oldid=16817
This article was adapted from an original article by L.N. Shevrin (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article