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Teerapong Suksumran

Publications and source records attributed to Teerapong Suksumran.

14 recordsLinked to original sources
arXiv2021

Geometry of gyrogroups via Klein's approach

Using Klein's approach, geometry can be studied in terms of a space of points and a group of transformations of that space. This allows us to apply algebraic tools in studying geometry of mathematical structures. In this article, we follow Klein's approach to study the geometry $(G, \mathcal{T})$, where $G$ is an abstract gyrogroup and $\mathcal{T}$ is an appropriate group of transformations containing all gyroautomorphisms of $G$. We focus on $n$-transitivity of gyrogroups and also give a few characterizations of coset spaces to be minimally invariant sets. We then prove that the collection of open balls of equal radius is a minimally invariant set of the geometry $(G, Γ_m)$ for any normed gyrogroup $G$, where $Γ_m$ is a suitable group of isometries of $G$.

math.GR↗
arXiv2021

An algorithm for finding minimal generating sets of finite groups

In this article, we study connections between components of the Cayley graph $\mathrm{Cay}(G,A)$, where $A$ is an arbitrary subset of a group $G$, and cosets of the subgroup of $G$ generated by $A$. In particular, we show how to construct generating sets of $G$ if $\mathrm{Cay}(G,A)$ has finitely many components. Furthermore, we provide an algorithm for finding minimal generating sets of finite groups using their Cayley graphs.

math.GR↗
arXiv2020

On transitivity and connectedness of Cayley graphs of gyrogroups

In this work, we explore edge direction, transitivity, and connectedness of Cayley graphs of gyrogroups. More specifically, we find conditions for a Cayley graph of a gyrogroup to be undirected, transitive, and connected. We also show a relationship between the cosets of a certain type of subgyrogroups and the connected components of Cayley graphs. Some examples regarding these findings are provided.

math.GR↗
arXiv2020

Frobenius reciprocity on the space of functions invariant under a group action

This article studies connections between group actions and their corresponding vector spaces. Given an action of a group $G$ on a nonempty set $X$, we examine the space $L(X)$ of scalar-valued functions on $X$ and its fixed subspace: $$ L^G(X) = \{f\in L(X)\colon f(a\cdot x) = f(x) \textrm{ for all }a\in G, x\in X\}. $$ In particular, we show that $L^G(X)$ is an invariant of the action of $G$ on $X$. In the case when the action is finite, we compute the dimension of $L^G(X)$ in terms of fixed points of $X$ and prove several prominent results for $L^G(X)$, including Bessel's inequality and Frobenius reciprocity.

math.GR↗
arXiv2019

The isometry group of $n$-dimensional Einstein gyrogroup

The space of $n$-dimensional relativistic velocities normalized to $c = 1$, $$\mathbb{B} = \{\mathbf{v}\in\mathbb{R}^n\colon \|\mathbf{v}\| < 1\},$$ is naturally associated with Einstein velocity addition $\oplus_E$, which induces the rapidity metric $d_E$ on $\mathbb{B}$ given by $d_E(\mathbf{u}, \mathbf{v}) = \tanh^{-1}\|-\mathbf{u}\oplus_E\mathbf{v}\|$. This metric is also known as the Cayley-Klein metric. We give a complete description of the isometry group of $(\mathbb{B}, d_E)$, along with its composition law.

math.MG↗
arXiv2019

Geometry of generated groups with metrics induced by their Cayley color graphs

Let $G$ be a group and let $S$ be a generating set of $G$. In this article, we introduce a metric $d_C$ on $G$ with respect to $S$, called the cardinal metric. We then compare geometric structures of $(G, d_C)$ and $(G, d_W)$, where $d_W$ denotes the word metric. In particular, we prove that if $S$ is finite, then $(G, d_C)$ and $(G, d_W)$ are not quasi-isometric in the case when $(G, d_W)$ has infinite diameter and they are bi-Lipschitz equivalent otherwise. We also give an alternative description of cardinal metrics by using Cayley color graphs. It turns out that color-permuting and color-preserving automorphisms of Cayley digraphs are isometries with respect to cardinal metrics.

math.MG↗
arXiv2019

An inequality related to Möbius transformations

The open unit ball $\mathbb{B} = \{\mathbf{v}\in\mathbb{R}^n\colon\|\mathbf{v}\|<1\}$ is endowed with Möbius addition $\oplus_M$ defined by $$\mathbf{u}\oplus_M\mathbf{v} = \dfrac{(1 + 2\langle\mathbf{u},\mathbf{v}\rangle + \|\mathbf{v}\|^2)\mathbf{u} + (1 - \|\mathbf{u}^2)\mathbf{v}}{1 + \langle\mathbf{u},\mathbf{v}\rangle + \|\mathbf{u}\|^2\|\mathbf{v}\|^2\|}$$ for all $\mathbf{u},\mathbf{v}\in \mathbf{B}$. In this article, we prove the inequality $$ \dfrac{\|\mathbf{u}\|-\|\mathbf{v}\|}{1+\|\mathbf{u}\|\|\mathbf{v}\|}\leq \|\mathbf{u}\oplus_M \mathbf{v}\| \leq \dfrac{\|\mathbf{u}\|+\|\mathbf{v}\|}{1-\|\mathbf{u}\|\|\mathbf{v}\|} $$ in $\mathbb{B}$. This leads to a new metric on $\mathbb{B}$ defined by $$d_T(\mathbf{u},\mathbf{v}) = \tan^{-1}{\|-\mathbf{u}\oplus_M\mathbf{v}\|},$$ which turns out to be an invariant of Möbius transformations on $\mathbb{R}^n$ carrying $\mathbb{B}$ onto itself. We also compute the isometry group of $(\mathbb{B}, d_T)$ and give a parametrization of the isometry group by vectors and rotations.

math.MG↗
arXiv2018

On metric structures of normed gyrogroups

In this article, we indicate that the open unit ball in $n$-dimensional Euclidean space $\mathbb{R}^n$ admits norm-like functions compatible with the Poincaré and Beltrami$-$Klein metrics. This leads to the notion of a normed gyrogroup, similar to that of a normed group in the literature. We then examine topological and geometric structures of normed gyrogroups. In particular, we prove that the normed gyrogroups are homogeneous and form left invariant metric spaces and derive a version of the Mazur$-$Ulam theorem. We also give certain sufficient conditions, involving the right-gyrotranslation inequality and Klee's condition, for a normed gyrogroup to be a topological gyrogroup.

math.MG↗
arXiv2018

Extension of Maschke's theorem

In the present article, we examine linear representations of finite gyrogroups, following their group-counterparts. In particular, we prove the celebrated theorem of Maschke for gyrogroups, along with its converse. This suggests studying the left regular action of a gyrogroup $(G, \oplus)$ on the function space $$ L^{\mathrm{gyr}}(G) = \{f\in L(G)\colon \forall a, x, y, z\in G, f(a\oplus\mathrm{gyr}[x, y]z) = f(a\oplus z)\} $$ in a natural way, where $L(G)$ is the space of all functions from $G$ into a field.

math.RT↗
arXiv2016

Special subgroups of gyrogroups: Commutators, nuclei and radical

A gyrogroup is a nonassociative group-like structure modelled on the space of relativistically admissible velocities with a binary operation given by Einstein's velocity addition law. In this article, we present a few of groups sitting inside a gyrogroup $G$, including the commutator subgyrogroup, the left nucleus, and the radical of $G$. The normal closure of the commutator subgyrogroup, the left nucleus, and the radical of $G$ are in particular normal subgroups of $G$. We then give a criterion to determine when a subgyrogroup $H$ of a finite gyrogroup $G$, where the index $[G\colon H]$ is the smallest prime dividing $|G|$, is normal in $G$.

math.GR↗
arXiv2016

Bi-gyrogroup: The group-like structure induced by bi-decomposition of groups

The decomposition $Γ=BH$ of a group $Γ$ into a subset $B$ and a subgroup $H$ of $Γ$ induces, under general conditions, a group-like structure for $B$, known as a gyrogroup. The famous concrete realization of a gyrogroup, which motivated the emergence of gyrogroups into the mainstream, is the space of all relativistically admissible velocities along with a binary operation given by the Einstein velocity addition law of special relativity theory. The latter leads to the Lorentz transformation group $\mathrm{SO}(1,n)$, $n\in\mathbb{N}$, in pseudo-Euclidean spaces of signature $(1, n)$. The study in this article is motivated by generalized Lorentz groups $\mathrm{SO}(m, n)$, $m, n\in\mathbb{N}$, in pseudo-Euclidean spaces of signature $(m, n)$. Accordingly, this article explores the bi-decomposition $Γ= H_LBH_R$ of a group $Γ$ into a subset $B$ and subgroups $H_L$ and $H_R$ of $Γ$, along with the novel bi-gyrogroup structure of $B$ induced by the bi-decomposition of $Γ$. As an example, we show by methods of Clifford algebras that the quotient group of the spin group $\mathrm{spin}(m, n)$ possesses the bi-decomposition structure.

math.GR↗
arXiv2016

Gyrogroup actions: A generalization of group actions

This article explores the novel notion of gyrogroup actions, which is a natural generalization of the usual notion of group actions. As a first step toward the study of gyrogroup actions from the algebraic viewpoint, we prove three well-known theorems in group theory for gyrogroups: the orbit-stabilizer theorem, the orbit decomposition theorem, and the Burnside lemma (or the Cauchy-Frobenius lemma). We then prove that under a certain condition, a gyrogroup $G$ acts transitively on the set $G/H$ of left cosets of a subgyrogroup $H$ in $G$ in a natural way. From this we prove the structure theorem that every transitive action of a gyrogroup can be realized as a gyrogroup action by left gyroaddition. We also exhibit concrete examples of gyrogroup actions from the Möbius and Einstein gyrogroups.

math.GR↗
arXiv2014

Isomorphism Theorems for Gyrogroups and L-Subgyrogroups

We extend well-known results in group theory to gyrogroups, especially the isomorphism theorems. We prove that an arbitrary gyrogroup $G$ induces the gyrogroup structure on the symmetric group of $G$ so that Cayley's Theorem is obtained. Introducing the notion of L-subgyrogroups, we show that an L-subgyrogroup partitions $G$ into left cosets. Consequently, if $H$ is an L-subgyrogroup of a finite gyrogroup $G$, then the order of $H$ divides the order of $G$.

math.GR↗