Fouad Zitan | Searcharxiv

arXiv2022

Bernstein algebras that are algebraic and the Kurosh problem

We study the class of Bernstein algebras that are algebraic, in the sense that each element generates a finite-dimensional subalgebra. Every Bernstein algebra has a maximal algebraic ideal, and the quotient algebra is a zero-multiplication algebra. Several equivalent conditions for a Bernstein algebra to be algebraic are given. In particular, known characterizations of train Bernstein algebras in terms of nilpotency are generalized to the case of locally train algebras. Along the way, we show that if a Banach Bernstein algebra is algebraic (respectively, locally train), then it is of bounded degree (respectively, train). Then we investigate the Kurosh problem for Bernstein algebras: whether a finitely generated Bernstein algebra which is algebraic of bounded degree is finite-dimensional. This problem turns out to have a closed link with a question about associative algebras. In particular, when the barideal is nil, the Kurosh problem asks whether a finitely generated Bernstein-train algebra is finite-dimensional. We prove that the answer is positive for some specific cases and for low degrees, and construct counter-examples in the general case. By results of Yagzhev, the Jacobian conjecture is equivalent to a certain statement about Engel and nilpotence identities of multioperator algebras. We show that the generalized Jacobian conjecture for quadratic mappings holds for Bernstein algebras.

math.RA↗

arXiv2018

On Bernstein algebras satisfying chain conditions II

Following a previous work with Boudi, we continue to investigate Bernstein algebras satisfying chain conditions. First, it is shown that a Bernstein algebra $(A, ω)$ with ascending or descending chain condition on subalgebras is finite-dimensional. We also prove that $A$ is Nœtherian (Artinian) if and only if its barideal $N=\ker(ω)$ is. Next, as a generalization of Jordan and nuclear Bernstein algebras, we study whether a Nœtherian (Artinian) Bernstein algebra $A$ with a locally nilpotent barideal $N$ is finite-dimensional. The response is affirmative in the Nœtherian case, unlike in the Artinian case. This question is closely related to a result by Zhevlakov on general locally nilpotent nonassociative algebras that are Nœtherian, for which we give a new proof. In particular, we derive that a commutative nilalgebra of nilindex 3 which is Nœtherian or Artinian is finite-dimensional. Finally, we improve and extend some results of Micali and Ouattara to the Nœtherian and Artinian cases.

math.RA↗