Facultatea de Matematică şi Informatică / Faculty of Methematics and Informatics

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    ON RECURSIVELY DIFFERENTIABLE QUASIGROUPS
    (2015) Larionova-Cojocaru, Inga
    If ( ),Q ⋅ is a binary groupoid then will denote its recursive derivative of order s by „ s ⋅ ”, hence 0 1 2 1 , , , ( ) ( ), s s s x y x y x y y xy x y x y x y − − ⋅ = ⋅ ⋅ = ⋅ ⋅ = ⋅ ⋅ ⋅K for every , .x y Q∈ If the recursive derivatives „ s ⋅ ”, s=1,2,…,k, of a binary quasigroup ( ),Q ⋅ are quasigroup operations, then ( ),Q ⋅ is called recursively k- differentiable. The notions of recursive derivatives and recursively differentiable quasigroups raised in the algebraic coding theory [1]. Recursively differentiable binary quasigroups in particular groups, are studied in the present paper. Proposition 1. If a quasigroup ( ),Q ⋅ , with the left unit, is recursively 1- differentiable then the mapping 2 x x→ is a bijection. Proposition 2. A diassociative loop ( ),Q ⋅ is recursively 1-differentiable if and only if the mapping 2 x x→ is a bijection. Corollary 1. A Moufang loop ( ),Q ⋅ , in particular a group, is recursively 1- differentiable if and only if the mapping 2 x x→ is a bijection on Q . Corollary 2. Finite groups of even order are not recursively 1-differentiable.
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    SUBGRAFURILE B-STABILE ÎN ORIENTAREA TRANZITIVĂ A GRAFURILOR
    (2015) Grigoriu, Nicolae
    Se formulează rezultate noi ce țin de studierea problemei orientării tranzitive a grafurilor neorientate. Amintim că un graf 𝐺𝐺⃗ = 𝑋𝑋; 𝑈𝑈 este tranzitiv orientat dacă pentru oricare trei vârfuri 𝑥𝑥, 𝑦𝑦, 𝑧𝑧 ∈ 𝑋𝑋 este satisfăcută relația de tranzitivitate: [𝑥𝑥, 𝑦𝑦] ∈ 𝑈𝑈 & [𝑦𝑦, 𝑧𝑧] ∈ 𝑈𝑈 ⇒ [𝑥𝑥, 𝑧𝑧] ∈ 𝑈𝑈 [3]. Graful neorientat 𝐺𝐺 = (𝑋𝑋; 𝑈𝑈) este tranzitiv orientabil dacă atribuind o anumită orientare muchiilor sale obținem un graf tranzitiv orientat. Un subgraf determinat de o mulțime de vârfuri 𝐴𝐴, se va numi subgraf stabil dacă pentru orice vârf 𝑥𝑥 ∈ 𝑋𝑋 ∖ 𝐴𝐴 se verifică una din relațiile: [𝑥𝑥, 𝑦𝑦] ∈ 𝑈𝑈𝐺𝐺 sau [𝑦𝑦, 𝑥𝑥] ∉ 𝑈𝑈𝐺𝐺, unde ∀𝑦𝑦 ∈ 𝐴𝐴.[1], [3] Definiția 1.[2] Subgraful stabil 𝐹𝐹 se numește subgraf B-stabil dacă pentru orice subgraf stabil 𝑀𝑀 din 𝐺𝐺 = (𝑋𝑋; 𝑈𝑈) are loc una din relațiile: 𝐹𝐹 ⊆ 𝑀𝑀 ∨ 𝐹𝐹 ∩ 𝑀𝑀 = ∅ Reieșind din definiția subgrafului B-stabil rezultă, că dacă 𝐺𝐺 nu conține subgraf stabil atunci acesta nu conține nici subgraf B-stabil. Lema 1. Dacă graful 𝐺𝐺 conține subgraf stabil, atunci 𝐺𝐺 conține și subgraf B- stabil. Teorema 1. Subgraful 𝐹𝐹 al grafului tranzitiv orientabil 𝐺𝐺 este B-stabil dacă și numai dacă orientarea tranzitivă 𝐹𝐹⃗ se construiește în mod independent de orientarea tranzitivă a întregului graf 𝐺𝐺.
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    ON INTELLIGENT SOFTWARE TOOLS IN SOLVING OF INTEGRAL EQUATIONS OF SECOND KIND
    (2015) Carmocanu, Gheorghe; Căpăţână, Gheorghe; Seiciuc, Eleonora; Seiciuc, Vladislav
    The Intelligent Support System for approximate solving of the Fredholm and Volterra integral equations of the second kind are developed. Some components for Computing Modules of the Intelligent Support System for solving of regular integral equations of second kind with spline-collocations, splinequadratures and degenerated kernel methods are proposed.
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    ASUPRA GRUPULUI MULTIPLICATIV AL BUCLELOR MEDII BOL
    (CEP USM, 2014) Grecu, Ion
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    ON RECURSIVE DIFFERENTIABILITY OF BINARY QUASIGROUPS
    ("VALINEX", 2014) Larionova-Cojocaru, Inga; Syrbu, Parascovia
    A quasigroup is called recursively n-differentiable if its first n recursive derivatives are quasigroups. The class of recursively differential quasigroups is arisen in the theory of MDS codes, in early 2000. Connections between recursive derivatives of different order are found in the present work. It is shown that isomorphic quasigroups have isomorphic recursive derivatives of any order. Also, it is proved that, if the recursive derivative of order one of a finite quasigroup (Q, ·) is commutative, then its group of inner mappings is a subgrup of the group of inner mappings of (Q, ·), of the same index as their corresponding multiplication groups.
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    ON THE HOLOMORPH OF ¼-QUASIGROUPS OF TYPE T1
    ("VALINEX", 2014) Ceban, Dina; Syrbu, Parascovia
    Quasigroups satisfying the identity x¢(x¢(x¢y)) = y are called ¼-quasigroups of type T1. Necessary and su±cient conditions for the holomorph of a ¼-quasigroup of type T1 to be a ¼-quasigroup of type T1 are established. Also, it is proved that the left (right) multiplication group of a ¼-quasigroup of type T1 is isomorphic to some normal subgroup of the left (right) multiplication group of its holomorph, respectively.
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    THE CONVEXITY IN THE COMPLEX OF MULTI-ARY RELATIONS
    (Romanian Society of Applied & Industrial Mathematics Universitatea din Pitesti, 2015) Braguţă, Galina; Cataranciuc, Sergiu
    For a complex of multi-ary relations [12] it is defined the concept of (k,m)-chain which is a generalization of the concept of chain known from the graph theory. Using (k,m)- chains it is introduced the concept of the distance function and it is proved that this function generate a convexity in the complex of multi-ary relations. It is operating with the concepts of convexity and convex hull, axiomatically defined by F.Levi [29] and we describe the iterative procedure to construct a convex hull for a subset of elements from the complex of multi-ary relations. [ABSTRACT FROM AUTHOR]