Journal of Algebra and Its Applications最新文献

A numerical semigroup $M$ is a subset of the non-negative integers that is closed under addition. A factorization of $n\in M$ is an expression of $n$ as a sum of generators of $M$, and the Graver basis of $M$ is a collection $\mathrm{\text{Gr}}(M_t)$ of trades between the generators of $M$ that allows for efficient movement between factorizations. Given positive integers $r_1,\dots ,r_k$, consider the family $M_t=〈t+r_1,\dots ,t+r_k$ of “shifted” numerical semigroups whose generators are obtained by translating $r_1,\dots ,r_k$ by an integer parameter $t$. In this paper, we characterize the Graver basis $\mathrm{\text{Gr}}(M_t)$ of $M_t$ for sufficiently large $t$ in the case

In this paper, first we give the notion of a crossed homomorphism on a $3$-Lie algebra with respect to an action on another $3$-Lie algebra, and characterize it using a homomorphism from a 3-Lie algebra to the semidirect product 3-Lie algebra. We also establish the relationship between crossed homomorphisms and relative Rota–Baxter operators of weight $1$ on 3-Lie algebras. Next we construct a cohomology theory for a crossed homomorphism on $3$-Lie algebras and classify infinitesimal deformations of crossed homomorphisms using the second cohomology group. Finally, using the higher derived brackets, we construct an $L_{\infty }$-algebra whose Maurer–Cartan elements are crossed homomorphisms. Consequently, we obtain the twisted $L_{\infty }$-algebra that controls deformations of a given crossed homomorphism on $3$-Lie algebras.

In this paper, the simple modules over the second quantized Weyl algebras at roots of unity over an algebraically closed field are classified.

We describe an algorithm for computing Macaulay dual spaces for multi-graded ideals. For homogeneous ideals, the natural grading is inherited by the Macaulay dual space which has been leveraged to develop algorithms to compute the Macaulay dual space in each homogeneous degree. Our main theoretical result extends this idea to multi-graded Macaulay dual spaces inherited from multi-graded ideals. This natural duality allows ideal operations to be translated from homogeneous ideals to their corresponding operations on the multi-graded Macaulay dual spaces. In particular, we describe a linear operator with a right inverse for computing quotients by a multi-graded polynomial. By using a total ordering on the homogeneous components of the Macaulay dual space, we also describe how to recursively construct a basis for each component. Several examples are included to demonstrate this new approach.

We proved in previous work that all real nilpotent Lie algebras of dimension up to $10$ carrying an ad-invariant metric are nice, i.e. they admit a nice basis in the sense of Lauret et al. In this paper, we show by constructing explicit examples that nonnice irreducible nilpotent Lie algebras admitting an ad-invariant metric exist for every dimension greater than $10$ and every nilpotency step greater than $2$. In the way of doing so, we introduce a method to construct Lie algebras with ad-invariant metrics called the single extension, as a parallel to the well-known double extension procedure.

This paper is devoted to the study of local and 2-local derivations of null-filiform, filiform and naturally graded quasi-filiform associative algebras. We prove that these algebras as a rule admit local derivations which are not derivations. We show that filiform and naturally graded quasi-filiform associative algebras admit 2-local derivations which are not derivations and any 2-local derivation of null-filiform associative algebras is a derivation.

We study a weak divisibility property for noncommutative rings: A nontrivial ring is fadelian if for all nonzero $a$ and $x$ there exist $b,c$ such that $x=ab+ca$. We prove properties of fadelian rings and construct examples thereof which are not division rings, as well as non-Noetherian and non-Ore examples.

We prove that every profinite $n$-ary group $(G,f)={\mathrm{\text{der}}}_{𝜃,b}(G,•)$ has a unique Haar measure $m_p$ and further for every measurable subset $A\subseteq G$, we have $$m_p(A)=m(A)=(n-1)m^{\ast }(A),$$ where $m$ and $m^{\ast }$ are the normalized Haar measures of the profinite groups $(G,•)$ and the Post cover $G^{\ast }$, respectively.

The notion of semifunctor between categories, due to [9], is defined as a functor that does not necessarily preserve identities. In this paper, we study how several properties of functors, such as fullness, full faithfulness, separability, natural fullness, can be formulated for semifunctors. Since a full semifunctor is actually a functor, we are led to introduce a notion of semifullness (and then semifull faithfulness) for semifunctors. In order to show that these conditions can be derived from requirements on the hom-set components associated with a semifunctor, we look at “semisplitting properties” for seminatural tranformations and we investigate the corresponding properties for morphisms whose source or target is the image of a semifunctor. We define the notion of naturally semifull semifunctor and we characterize natural semifullness for semifunctors that are part of a semiadjunction in terms of semisplitting conditions for the unit and counit attached to the semiadjunction. We study the behavior of semifunctors with respect to (semi)separability and we prove Rafael-type Theorems for (semi)separable semifunctors and a Maschke-type theorem for separable semifunctors. We provide examples of semifunctors on which we test the properties considered so far.

We show that a previously introduced key exchange based on a congruence-simple semiring action is not secure by providing an attack that reveals the shared key from the distributed public information for any of such semirings.