Tag - Non-associative rings

David Fernández: Non-commutative Poisson geometry and pre-Calabi-Yau algebras

2nd December, 2024

In order to define suitable non-commutative Poisson structures, M. Van den Bergh introduced double Poisson algebras and double quasi-Poisson algebras. Furthermore, N. Iyudu and M. Kontsevich found an insightful correspondence between double Poisson algebras and pre-Calabi-Yau algebras; certain cyclic A∞-algebras which can be seen as non-commutative versions of shifted Poisson manifolds. In this talk, I will present an extension of the Iyudu-Kontsevich correspondence to the differential graded setting. I will also explain how double quasi-Poisson algebras give rise to pre-Calabi-Yau algebras.

Pablo Zadunaisky: Clebsch-Gordan revisited

19th November, 2024

By an ultra classical result, the tensor product of a simple representation of 𝔤𝔩n(ℂ) and its defining representation decomposes as a direct sum of simple representations without multiplicities. This means that for each highest weight, the space of highest weight vectors is 1-dimensional. We will give an explicit construction of these highest weight vectors, and show that they arise from the action of certain elements in the enveloping algebra of 𝔤𝔩n(ℂ) + 𝔤𝔩n(ℂ) on the tensor product. These elements are independent of the simple representation we started with, and in fact produce highest weight vectors in several other contexts.

Carla Rizzo: Differential identities, almost polynomial growth and matrix algebras

11th November, 2024

Let F be a field of characteristic zero, L a Lie algebra over F, and A an L-algebra - that is, an associative algebra over F with an action of L induced by derivations. This action of L on A can be extended to an action of its universal enveloping algebra U(L), leading to the concept of L-identities or differential identities of A: polynomials in variables xu:= u(x), where u ∈ U(L), that vanish under all substitutions of elements from A. Differential identities were first introduced by Kharchenko in 1978, and, in later years, subsequent work by Gordienko and Kochetov has spurred a renewed interest in both their structure and quantitative properties. In this talk, I will present recent results on the differential identities of matrix L-algebras, with a particular focus on their classification and growth behaviour.

Fernando Montaner: Pairs of quotients of Jordan pairs

4th November, 2024

In this talk, we expose ongoing joint work with I Paniello on systems of quotients (in a sense partially extending the localization theory of Jordan algebras, which in turn is inspired by the localization theory of associative algebras). Localization theory in associative algebras originated in the purpose of extending the construction of fields of quotients of integral domains, and therefore in the purpose of defining ring extensions in which a selected set of elements become invertible. As it is well known in associative theory that led to Goldie's theorems, and these in turn to more general localization theories for which the denominators of the fraction-like elements of the extensions are (one-sided) ideals taken in a class of filters (Gabriel filters). These ideas have been partially extended to Jordan algebras by several authors (starting with Zelmanov's version of Goldie theory in the Jordan setting, and its extension by Fernandez López-García Rus and Montaner) and Paniello and Montaner (among others) definition of algebras of quotients of Jordan algebras. Following the development of Jordan theory, a natural direction for extending these results is considering the context of Jordan pairs. This is the objective of the research presented here. Since obviously, a Jordan pair cannot have invertible elements unless it is an algebra, and in this case, we are back in the already developed theory, the kind of quotients that would make a significative (proper) extension of the case of algebras should be based in a different notion of the quotient. An approach that seems to be promising is considering the Jordan extension of Fountain and Gould notion of local order, as has been adapted to Jordan algebras by the work of Fernández López, and more recently by Montaner and Paniello with the notion of local order, in which the bridge between algebras and pairs is established by local algebras following the ideas of D'Amour and McCrimmon. In the talk, this idea is exposed, together with the state of the research, and the open problems that it raises.

Raschid Abedin: Classification of D-bialgebras via algebraic geometry

28th October, 2024

In a now classic paper, Belavin and Drinfeld categorized solutions to the classical Yang-Baxter equation (CYBE), an equation crucial to the theory of integrable systems, into three classes: elliptic, trigonometric and rational. It is possible to reproduce this result by geometrizing solutions of the CYBE and then applying algebro-geometric methods. In this talk, we will explain how this approach can be used to categorize Lie bialgebra structures on power series Lie algebras, as well as non-associative generalizations of these structures: D-bialgebra structures on more general power series algebras.

Ilya Chevyrev: Pre-Lie algebras in stochastic PDEs

21st October, 2024

In this talk, I will discuss a general method to renormalize singular stochastic partial differential equations (SPDEs) using the theory of regularity structures. It turns out that, to derive the renormalized equation, one can employ a convenient multi-pre-Lie algebra. The pre-Lie products in this algebra are reminiscent of the pre-Lie product on the Grossman-Larson algebra of trees, but come with several important twists. For the renormalization of SPDEs, the important feature of this multi-pre-Lie algebra is that it is free in a certain sense.

Slaven Kožić: Representations of the quantum affine vertex algebra associated with the trigonometric R-matrix of A

14th October, 2024

One important problem in the vertex algebra theory is to associate certain vertex algebra-like objects, the quantum vertex algebras, to various classes of quantum groups, such as quantum affine algebras or double Yangians. In this talk, I will discuss this problem in the context of Etingof-Kazhdan's quantum affine vertex algebra Vc(𝔤𝔩N) associated with the trigonometric R-matrix of type A. The main focus will be on the explicit description of the centre of Vc(𝔤𝔩N) at the critical level c = -N and, furthermore, on the connection between certain classes of Vc(𝔤𝔩N)-modules and representation theories of the quantum affine algebra of type A and the orthogonal twisted h-Yangian.

Ana Agore: Solutions of the set-theoretic Yang-Baxter equation of Frobenius-Separability (FS) type

7th October, 2024

We investigate a special class of solutions of the set-theoretic Yang-Baxter equation, called Frobenius-Separability (FS) type solutions. In particular, we show that the category of solutions of the set-theoretic Yang-Baxter equation of Frobenius-Separability (FS) type is equivalent to the category of pointed Kimura semigroups. As applications, all involutive, idempotent, non-degenerate, surjective, finite order, unitary, or indecomposable solutions of FS type are classified. For instance, if |X| = n, then the number of isomorphism classes of all such solutions on X that are (a) left non-degenerate, (b) bijective, (c) unitary or (d) indecomposable and left-non-degenerate is: (a) the Davis number d(n), (b) Σm|n p(m), where p(m) is the Euler partition number, (c) τ(n) + Σd|n[d/2], where τ is the number of divisors of n, or (d) the Harary number. The automorphism groups of such solutions can also be recovered as automorphism groups Aut(f) of sets X equipped with a single endo-function f : X → X. We describe all groups of the form Aut(f) as iterations of direct and (possibly infinite) wreath products of cyclic or full symmetric groups, characterize the abelian ones as products of cyclic groups, and produce examples of symmetry groups of FS solutions not of the form Aut(f).

Arne Van Antwerpen: Indecomposable and simple solutions of the Yang-Baxter equation

30th September, 2024

Recall that a set-theoretic solution of the Yang-Baxter equation is a tuple (X,r), where X is a non-empty set and r: X × X → X × X a bijective map such that

(r × idX) (idX × r) (r × idX) = (idX × r) (r × idX) (idX × r),

where one denotes r(x,y)=(lx(y), ry(x)). Attention is often restricted to so-called non-degenerate solutions, i.e. lx and ry are bijective. We will call these solutions for short in the remainder of this abstract. To understand more general objects, it is an important technique to study 'minimal' objects and glue them together. For solutions both indecomposable and simple solutions fit the bill for being a minimal object. In this talk, we will report on recent work with I. Colazzo, E. Jespers and L. Kubat on simple solutions. In particular, we will discuss an extension of a result of M. Castelli that allows to identify whether a solution is simple, without having to know or calculate all smaller solutions. This method employs so-called skew braces, which were constructed to provide more examples of solutions, but also govern many properties of general solutions. In the latter part of the talk, we discuss the extension of a method to construct new indecomposable or simple solutions from old ones via cabling, originally introduced by V. Lebed, S. Ramirez, and L. Vendramin to unify the known results on indecomposability of solutions.

Ignacio Bajo: Quadratic Lie algebras admitting 2-plectic structures

23rd September, 2024

A 2-plectic form ω on a Lie algebra is a 3-form on the algebra such that it is closed and non-degenerate in the sense that, for every non-zero x, the bilinear form ω(x, ·, ·) is not identically zero. We will study the existence of 2-plectic structures on the so-called quadratic Lie algebras, which are Lie algebras admitting an ad-invariant pseudo-Euclidean product. It is well-known that every centreless quadratic Lie algebra admits a 2-plectic form but not many quadratic examples with non-trivial centre are known. We give several constructions to obtain large families of 2-plectic quadratic Lie algebras with non-trivial centre, many of them among the class of nilpotent Lie algebras. We give some sufficient conditions to assure that certain extensions of 2-plectic quadratic Lie algebras result to be 2-plectic as well. For instance, we show that oscillator algebras can be naturally endowed with 2-plectic structures. We prove that every quadratic and symplectic Lie algebra with dimension greater than 4 also admits a 2-plectic form. Further, conditions to assure that one may find a 2-plectic which is exact on certain quadratic Lie algebras are obtained.