Algebra, Combinatorics and Number Theory

Generalized polynomial identities and $2 \times 2$ upper triangular matrices

Let $A$ be an associative algebra over a field $F$ of characteristic zero, $F\langle X \rangle$ be the free algebra generated by the countable set $X=\{x_1,x_2,\ldots \}$ and $W$ be a unitary algebra over $F$. Then $A$ is called $W$-algebra if it has a structure of $W$-bimodule with some additional conditions. 

On the Kantor product and conservative algebras

In 1972, Kantor introduced the class of conservative algebras, which contains many other important classes of algebras, for example, associative, Lie, Jordan, and Leibniz algebras. Initially, we will discuss some known results about conservative algebras, and especially the algebra $U(n)$ (space of bilinear multiplications on the n-dimensional space $V_n$). Then, we will present results obtained on the study of the Kantor product (product defined in $U(n)$). In particular, we will study the Kantor product of some finite-dimensional algebras.

Standard Majorana representations of 3-transposition groups

The Monster group $M$ is the largest sporadic simple group. It is also the group of automorphisms of $196, 884$-dimensional Fischer-Norton-Griess algebra $V_M$. In 2009, A. A. Ivanov offered an axiomatic approach to studying the structure of $V_M$ by introducing the notions of Majorana algebra and Majorana representation. Later, the theory developed, and Majorana representations of several groups were constructed. Our talk is dedicated to the existence of standard Majorana representations of 3-transposition groups for the Fischer list.

On pyramidal groups of prime power degree

A Kirkman Triple System (KTS) is called $m$-pyramidal if there exists a subgroup $G$ of its automorphism group that fixes $m$ points of the KTS and acts regularly on the other points. Such a group $G$ admits a unique conjugacy class $C$ of involutions (elements of order 2) and $|C|=m$. We call groups with this property $m$-pyramidal. We prove that, if $m$ is an odd prime power $p^k$, then every $m$-pyramidal group is solvable if and only if either $m=9$ or $k$ is odd. We also determine the sizes of the vertex sets of the $m$-pyramidal KTS when $m$ is a prime number.

Uma abordagem categórica para ações parciais de monoides

Seguindo a ideia no artigo de Hu e Vercruysse [1], introduzimos morfismos parciais em uma categoria arbitrária $\textbf{C}$, de modo que ações parciais de um monoide $M$ em um conjunto $X$ correspondem a certas funções de $M$ para o conjunto de classes de isomorfismo de morfismos parciais de $X$ para $X$ na categoria de conjuntos.

Generalized torsion elements in groups

In this talk we present some properties of generalized torsion elements in groups. Moreover, we try connect this "new'' concept with the usual concept of torsion in some standard class of groups (e.g., nilpotent, FC-groups). This presentation is mainly based in the following papers [1,2,3,4]. This is joint work with C. Schneider and D. Silveira.   
      

References

[1] R. Bastos, C. Schneider and D. Silveira. Generalized torsion elements in groups.  To appear in Arch. Math. Basel (2023), arXiv:2302.09589.  

The invariant ring of pair of matrices

Let us consider the action of the general linear group $\mathrm{GL}_n(\mathbb{C})$ on the direct product $\mathcal{M}_n^d$
of $d$ copies of $\mathcal{M}_n$ by simultaneous conjugation sending $(X_1,\ldots, X_d)$ to $(gX_1g^{-1},\ldots,gX_dg^{-1})$
for any $g\in \mathrm{GL}_n(\mathbb{C})$ . This induces an action of $\mathrm{GL}_n(\mathbb{C})$ on the algebra $\mathbb{C}[\mathcal{M}_n^d]$ of polynomial
functions on $\mathcal{M}_n^d$. The algebra of invariants under this action, $\mathbb{C}[\mathcal{M}_n^d]^{\mathrm{GL}_n}$, is an important

The Grassmann convexity Shapiro-Shapiro conjecture

The Grassmann convexity conjecture by B. Shapiro and M. Shapiro admits
several equivalent formulations.
One of them gives a conjectural formula for the maximal total number
of real zeros of the consecutive Wronskians of an arbitrary
fundamental solution to a disconjugate linear ordinary differential
equation with real time.
Another formulation is in terms of convex curves in the nilpotent
lower triangular group.
There is a very elementary formulation in terms of lists of vectors in $\mathbb{R}^k$.

Coberturas por dominós de cilindros

Vamos considerar a conectividade de coberturas por dominós usando movimentos locais.
Em particular, nos concentraremos no movimento conhecido como flip, no qual dois dominós adjacentes são removidos e recolocados em outra posição.
Em dimensão 2, é possível ligar quaisquer duas coberturas de uma região simplesmente conexa por meio de uma sequência de flips.
No entanto, em dimensão 3, existem regiões simplesmente conexas onde flips não são suficientes para conectar qualquer par de coberturas.