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Class preserving mappings of equivalence systems

Ivan Chajda (2004)

Acta Universitatis Palackianae Olomucensis. Facultas Rerum Naturalium. Mathematica

By an equivalence system is meant a couple 𝒜 = ( A , θ ) where A is a non-void set and θ is an equivalence on A . A mapping h of an equivalence system 𝒜 into ℬ is called a class preserving mapping if h ( [ a ] θ ) = [ h ( a ) ] θ ' for each a ∈ A . We will characterize class preserving mappings by means of permutability of θ with the equivalence Φ h induced by h .

Clausal relations and C-clones

Edith Vargas (2010)

Discussiones Mathematicae - General Algebra and Applications

We introduce a special set of relations called clausal relations. We study a Galois connection Pol-CInv between the set of all finitary operations on a finite set D and the set of clausal relations, which is a restricted version of the Galois connection Pol-Inv. We define C-clones as the Galois closed sets of operations with respect to Pol-CInv and describe the lattice of all C-clones for the Boolean case D = {0,1}. Finally we prove certain results about C-clones over a larger set.

Completely dissociative groupoids

Milton Braitt, David Hobby, Donald Silberger (2012)

Mathematica Bohemica

In a groupoid, consider arbitrarily parenthesized expressions on the k variables x 0 , x 1 , ⋯ x k - 1 where each x i appears once and all variables appear in order of their indices. We call these expressions k -ary formal products, and denote the set containing all of them by F σ ( k ) . If u , v ∈ F σ ( k ) are distinct, the statement that u and v are equal for all values of x 0 , x 1 , ⋯ x k - 1 is a generalized associative law. Among other results, we show that many small groupoids are completely dissociative, meaning that no generalized associative law holds...

Composition of axial functions of products of finite sets

Krzysztof Płotka (2007)

Colloquium Mathematicae

We show that every function f: A × B → A × B, where |A| ≤ 3 and |B| < ω, can be represented as a composition f₁ ∘ f₂ ∘ f₃ ∘ f₄ of four axial functions, where f₁ is a vertical function. We also prove that for every finite set A of cardinality at least 3, there exist a finite set B and a function f: A × B → A × B such that f ≠ f₁ ∘ f₂ ∘ f₃ ∘ f₄ for any axial functions f₁, f₂, f₃, f₄, whenever f₁ is a horizontal function.

Disjoint and complete unions of incidence structures

František Machala, Marek Pomp (1997)

Mathematica Bohemica

Some decompositions of general incidence structures with regard to distinguished components (modular or simple) are considered and several structure theorems for them are deduced.

Distributivity of lattices of binary relations

Ivan Chajda (2002)

Mathematica Bohemica

We present a formal scheme which whenever satisfied by relations of a given relational lattice L containing only reflexive and transitive relations ensures distributivity of L .

Double n -ary relational structures

Jiří Karásek (1997)

Mathematica Bohemica

In [7], V. Novak and M. Novotny studied ternary relational structures by means of pairs of binary structures; they obtained the so-called double binary structures. In this paper, the idea is generalized to relational structures of any finite arity.

Currently displaying 21 – 40 of 137