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====References====
 
====References====
 
<table>
 
<table>
<TR><TD valign="top">[1]</TD> <TD valign="top"> H. Prüfer,   "Theorie der Abelschen Gruppen"  ''Math. Z.'' , '''20'''  (1924)  pp. 165–187</TD></TR>
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<TR><TD valign="top">[1]</TD> <TD valign="top"> H. Prüfer, "Theorie der Abelschen Gruppen"  ''Math. Z.'' , '''20'''  (1924)  pp. 165–187</TD></TR>
<TR><TD valign="top">[2]</TD> <TD valign="top"> R. Baer,   "Zur Einführung des Scharbegriffs"  ''J. Reine Angew. Math.'' , '''160'''  (1929)  pp. 199–207</TD></TR>
+
<TR><TD valign="top">[2]</TD> <TD valign="top"> R. Baer, "Zur Einführung des Scharbegriffs"  ''J. Reine Angew. Math.'' , '''160'''  (1929)  pp. 199–207</TD></TR>
<TR><TD valign="top">[3]</TD> <TD valign="top"> J. Certaine,   "The ternary operation $(abc)=ab^{-1}c$ of a group"  ''Bull. Amer. Math. Soc.'' , '''49'''  (1943)  pp. 869–877</TD></TR>
+
<TR><TD valign="top">[3]</TD> <TD valign="top"> J. Certaine, "The ternary operation $(abc)=ab^{-1}c$ of a group"  ''Bull. Amer. Math. Soc.'' , '''49'''  (1943)  pp. 869–87 {{ZBL|0061.02305}}7</TD></TR>
<TR><TD valign="top">[4]</TD> <TD valign="top"> V.V. Vagner,   "The theory of generalized heaps and of generalized groups"  ''Mat. Sb.'' , '''32''' :  3  (1953)  pp. 545–632  (In Russian)</TD></TR>
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<TR><TD valign="top">[4]</TD> <TD valign="top"> V.V. Vagner, "The theory of generalized heaps and of generalized groups"  ''Mat. Sb.'' , '''32''' :  3  (1953)  pp. 545–632  (In Russian)</TD></TR>
<TR><TD valign="top">[5]</TD> <TD valign="top"> V.V. Vagner,   "Foundations of differential geometry and contemporary algebra" , ''Proc. 4-th All-Union. Mat. Conf.'' , '''1''' , Leningrad  (1963)  pp. 17–29  (In Russian)</TD></TR>
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<TR><TD valign="top">[5]</TD> <TD valign="top"> V.V. Vagner, "Foundations of differential geometry and contemporary algebra" , ''Proc. 4-th All-Union. Mat. Conf.'' , '''1''' , Leningrad  (1963)  pp. 17–29  (In Russian)</TD></TR>
<TR><TD valign="top">[6]</TD> <TD valign="top"> M. Flato,   "Deformation view of physical theories"  ''Czechoslovak J. Phys.'' , '''B32'''  (1982)  pp. 472–475</TD></TR>
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<TR><TD valign="top">[6]</TD> <TD valign="top"> M. Flato, "Deformation view of physical theories"  ''Czechoslovak J. Phys.'' , '''B32'''  (1982)  pp. 472–475</TD></TR>
 
</table>
 
</table>
  
 
====Comments====
 
====Comments====
The terms ''groud'', ''abstract coset'', ''restricted brigade'', ''Schar'' and ''flock'' are also found in the literature.
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The terms ''groud'', ''abstract coset'', ''imperfect brigade'', ''Schar'' and ''flock'' are also found in the literature.
  
 
====References====
 
====References====
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<TR><TD valign="top">[a1]</TD> <TD valign="top"> Bruck, Richard Hubert ''A survey of binary systems'', Ergebnisse der Mathematik und ihrer Grenzgebiete. Neue Folge. '''20''' Springer (1958) {{ZBL|0081.01704}} </TD></TR>
 
<TR><TD valign="top">[a1]</TD> <TD valign="top"> Bruck, Richard Hubert ''A survey of binary systems'', Ergebnisse der Mathematik und ihrer Grenzgebiete. Neue Folge. '''20''' Springer (1958) {{ZBL|0081.01704}} </TD></TR>
 
<TR><TD valign="top">[a2]</TD> <TD valign="top"> Hollings, Christopher ''Mathematics across the Iron Curtain: A History of the Algebraic Theory of Semigroups'', Amer. Math. Soc. (2014) {{ZBL|1317.20001}}  </TD></TR>
 
<TR><TD valign="top">[a2]</TD> <TD valign="top"> Hollings, Christopher ''Mathematics across the Iron Curtain: A History of the Algebraic Theory of Semigroups'', Amer. Math. Soc. (2014) {{ZBL|1317.20001}}  </TD></TR>
<TR><TD valign="top">[a3]</TD> <TD valign="top"> Schein, Boris "Inverse semigroups and generalised groups". In A.F. Lavrik. Twelve papers in logic and algebra. Amer. Math. Soc. Transl. 113. American Mathematical Society. pp. 89–182. ISBN 0-8218-3063-5 {{ZBL|0247.20060}} {{ZBL|0404.20055}}  </TD></TR>
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<TR><TD valign="top">[a3]</TD> <TD valign="top"> Schein, Boris "Inverse semigroups and generalised groups". In A.F. Lavrik. Twelve papers in logic and algebra. Amer. Math. Soc. Transl. 113. American Mathematical Society. pp. 89–182. {{ISBN|0-8218-3063-5}} {{ZBL|0247.20060}} {{ZBL|0404.20055}}  </TD></TR>
 
</table>
 
</table>

Latest revision as of 14:12, 12 November 2023

2020 Mathematics Subject Classification: Primary: 20N10 [MSN][ZBL]

Algebraic structures with one ternary operation that satisfies certain identities. Heaps are defined by the identities

$$[[x_1x_2x_3]x_4x_5]=[x_1x_2[x_3x_4x_5]],$$

$$[x_1x_1x_2]=x_2,\quad[x_1x_2x_2]=x_1,$$

while semi-heaps are defined by the identities

$$[[x_1x_2x_3]x_4x_5]=[x_1[x_4x_3x_2]x_5]=[x_1x_2[x_3x_4x_5]].$$

All heaps are also semi-heaps.

If, in the set $\Phi(A,B)$ of all one-to-one mappings of a set $A$ into a set $B$, one defines the ternary operation that puts an ordered triplet of mappings $\phi_1,\phi_2,\phi_3$ into correspondence with the mapping that is the composite of $\phi_1,\phi_2^{-1},\phi_3$, then $\Phi(A,B)$ is a heap. Any heap is isomorphic to some heap of one-to-one mappings. If a ternary operation is introduced into an arbitrary group $G$ by putting $[g_1g_2g_3]=g_1g_2^{-1}g_3$, a heap is obtained (the heap associated with the given group). The concept of a heap was introduced in the study of the above ternary operation on an Abelian group [1]. Heaps have been studied from their abstract aspect [2], [3]. In particular, it was shown by R. Baer [2] that if an arbitrary given element $s_0$ is fixed in a heap $S$, then the operations defined by the equations $s_1s_2=[s_1s_0s_2]$, $s^{-1}=[s_0ss_0]$ define a group structure on $S$ in which $s_0$ is the unit; the heap associated with this group coincides with the initial heap, while the groups obtained from a heap by fixing various elements of it are isomorphic. In other words, the variety of all heaps is equivalent to the variety of all groups.

The set $\mathfrak P(A,B)$ of all binary relations (cf. Binary relation) between the elements of two sets $A$ and $B$ is a semi-heap with respect to the triple multiplication $[\rho_1\rho_2\rho_3]=\rho_1\rho_2^{-1}\rho_3$. The set of all invertible partial mappings of $A$ into $B$ is also closed with respect to the triple multiplication and is a generalized heap [4], i.e. a semi-heap with the identities

$$[xxx]=x,$$

$$[x_1x_1[x_2x_2x_3]]=[x_2x_2[x_1x_1x_3]],$$

$$[[x_1x_2x_2]x_3x_3]=[[x_1x_3x_3]x_2x_2].$$

Generalized heaps find application in the foundations of differential geometry in the study of coordinate atlases [5]. Heaps are closely connected with semi-groups with involution. If an involution $\theta$, which is an anti-automorphism, is defined on a semi-group $S$, then the ternary operation $[s_1s_2s_3]=s_1\theta(s_2)s_3$ converts $S$ into a semi-heap. Any semi-heap is isomorphic to a sub-semi-heap of a semi-group with involution, [4].

References

[1] H. Prüfer, "Theorie der Abelschen Gruppen" Math. Z. , 20 (1924) pp. 165–187
[2] R. Baer, "Zur Einführung des Scharbegriffs" J. Reine Angew. Math. , 160 (1929) pp. 199–207
[3] J. Certaine, "The ternary operation $(abc)=ab^{-1}c$ of a group" Bull. Amer. Math. Soc. , 49 (1943) pp. 869–87 Zbl 0061.023057
[4] V.V. Vagner, "The theory of generalized heaps and of generalized groups" Mat. Sb. , 32 : 3 (1953) pp. 545–632 (In Russian)
[5] V.V. Vagner, "Foundations of differential geometry and contemporary algebra" , Proc. 4-th All-Union. Mat. Conf. , 1 , Leningrad (1963) pp. 17–29 (In Russian)
[6] M. Flato, "Deformation view of physical theories" Czechoslovak J. Phys. , B32 (1982) pp. 472–475

Comments

The terms groud, abstract coset, imperfect brigade, Schar and flock are also found in the literature.

References

[a1] Bruck, Richard Hubert A survey of binary systems, Ergebnisse der Mathematik und ihrer Grenzgebiete. Neue Folge. 20 Springer (1958) Zbl 0081.01704
[a2] Hollings, Christopher Mathematics across the Iron Curtain: A History of the Algebraic Theory of Semigroups, Amer. Math. Soc. (2014) Zbl 1317.20001
[a3] Schein, Boris "Inverse semigroups and generalised groups". In A.F. Lavrik. Twelve papers in logic and algebra. Amer. Math. Soc. Transl. 113. American Mathematical Society. pp. 89–182. ISBN 0-8218-3063-5 Zbl 0247.20060 Zbl 0404.20055
How to Cite This Entry:
Heaps and semi-heaps. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Heaps_and_semi-heaps&oldid=37058
This article was adapted from an original article by V.N. Salii (originator), which appeared in Encyclopedia of Mathematics - ISBN 1402006098. See original article