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A class of Bol loops with a subgroup of index two

Petr Vojtěchovský (2004)

Commentationes Mathematicae Universitatis Carolinae

Let G be a finite group and C 2 the cyclic group of order 2 . Consider the 8 multiplicative operations ( x , y ) ( x i y j ) k , where i , j , k { - 1 , 1 } . Define a new multiplication on G × C 2 by assigning one of the above 8 multiplications to each quarter ( G × { i } ) × ( G × { j } ) , for i , j C 2 . We describe all situations in which the resulting quasigroup is a Bol loop. This paper also corrects an error in P. Vojtěchovsk’y: On the uniqueness of loops M ( G , 2 ) .

A class of commutative loops with metacyclic inner mapping groups

Aleš Drápal (2008)

Commentationes Mathematicae Universitatis Carolinae

We investigate loops defined upon the product m × k by the formula ( a , i ) ( b , j ) = ( ( a + b ) / ( 1 + t f i ( 0 ) f j ( 0 ) ) , i + j ) , where f ( x ) = ( s x + 1 ) / ( t x + 1 ) , for appropriate parameters s , t m * . Each such loop is coupled to a 2-cocycle (in the group-theoretical sense) and this connection makes it possible to prove that the loop possesses a metacyclic inner mapping group. If s = 1 , then the loop is an A-loop. Questions of isotopism and isomorphism are considered in detail.

A class of quasigroups solving a problem of ergodic theory

Jonathan D. H. Smith (2000)

Commentationes Mathematicae Universitatis Carolinae

A pointed quasigroup is said to be semicentral if it is principally isotopic to a group via a permutation on one side and a group automorphism on the other. Convex combinations of permutation matrices given by the one-sided multiplications in a semicentral quasigroup then yield doubly stochastic transition matrices of finite Markov chains in which the entropic behaviour at any time is independent of the initial state.

A closure condition which is equivalent to the Thomsen condition in quasigroups.

M. A. Taylor (1983)


In this note it is shown that the closure condition, X1Y2 = X2Y1, X1Y4 = X2Y3, X3Y3 = X4Y1 --> X4Y2 = X3Y4, (and its dual) is equivalent to the Thomsen condition in quasigroups but not in general. Conditions are also given under which groupoids satisfying it are principal homotopes of cancellative, abelian semigroups, or abelian groups.

A dyadic view of rational convex sets

Gábor Czédli, Miklós Maróti, Anna B. Romanowska (2014)

Commentationes Mathematicae Universitatis Carolinae

Let F be a subfield of the field of real numbers. Equipped with the binary arithmetic mean operation, each convex subset C of F n becomes a commutative binary mode, also called idempotent commutative medial (or entropic) groupoid. Let C and C ' be convex subsets of F n . Assume that they are of the same dimension and at least one of them is bounded, or F is the field of all rational numbers. We prove that the corresponding idempotent commutative medial groupoids are isomorphic iff the affine space F n ...

A factorization of quasiorder hypergroups

Ivan Chajda, Šárka Hošková (2004)

Commentationes Mathematicae Universitatis Carolinae

The contribution is devoted to the question of the interchange of the construction of a quasiorder hypergroup from a quasiordered set and the factorization.

A geometric approach to universal quasigroup identities

Václav J. Havel (1993)

Archivum Mathematicum

In the present paper we construct the accompanying identity I ^ of a given quasigroup identity I . After that we deduce the main result: I is isotopically invariant (i.e., for every guasigroup Q it holds that if I is satisfied in Q then I is satisfied in every quasigroup isotopic to Q ) if and only if it is equivalent to I ^ (i.e., for every quasigroup Q it holds that in Q either I , I ^ are both satisfied or both not).

A groupoid characterization of Boolean algebras

Ivan Chajda (2004)

Discussiones Mathematicae - General Algebra and Applications

We present a groupoid which can be converted into a Boolean algebra with respect to term operations. Also conversely, every Boolean algebra can be reached in this way.

A groupoid characterization of orthomodular lattices

Ivan Chajda (2005)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

We prove that an orthomodular lattice can be considered as a groupoid with a distinguished element satisfying simple identities.

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