|Conţinutul numărului revistei|
| SM ISO690:2012|
GORACINOVA-ILIEVA, Lidija; MARKOVSKI, Smile; SOKOLOVA, Ana. On groupoids with identity x(xy) = y . In: Quasigroups and Related Systems. 2004, nr. 1(11), pp. 39-54. ISSN 1561-2848.
|Quasigroups and Related Systems|
|Numărul 1(11) / 2004 / ISSN 1561-2848|
The groupoid identity x(xy) = y appears in dening several classes of groupoids, such
as Steiner's loops which are closely related to Steiner's triple systems, the class of can-
cellative groupoids with property (2, 5), Boolean groups, and groupoids which exhibit
orthogonality of quasigroups. Its dual identity is one of the dening identities for the
variety of quasigroups corresponding to strongly 2-perfect m-cycle systems. In this paper
we consider the following varieties of groupoids: V = V ar(x(xy) = y), Vc = V ar(x(xy) =
y, xy = yx), Vu = V ar(x(xy) = y, (xy)y = xy), Vi = V ar(x(xy) = y, (xy)y = yx).
Suitable canonical constructions of free objects in each of these varieties are given and
several other structural properties are presented. Some problems of enumeration of
groupoids are also resolved. It is shown that each Vi -groupoid denes a Steiner quintuple
system and vice versa, implying existence of Steiner quintuple systems of enough large