arXiv subjects

Shashank Vikram Singh

Publications and source records attributed to Shashank Vikram Singh.

7 recordsLinked to original sources

arXiv2026

On real and rational elements in a class of Lie groups

For a class of groups $G$ over a field $\mathbb{F}$, including certain Lie groups, Algebraic groups and finite groups, we provide a general method to determine real and rational elements, thereby unifying earlier group-specific results into a wider framework. As an application, we classify all real and rational elements in the semidirect product ${\rm SL}(2,\mathbb{R}) \ltimes \mathrm{Sym}^n(\mathbb{R}^2)$. Moreover, we study real elements in connected real solvable Lie groups. It is easy to observe that if $G$ is a simply connected solvable real Lie group, then the identity is the only real element of $G$. Conversely, if the identity is the only real element of a connected real Lie group $G$, then $G$ is simply connected, solvable, and exponential, which turns out to be of independent interest.

math.GR↗

arXiv2026

Determining $\mathbb R$-Rank in Semisimple Lie Groups via uniform approximate Lattice arising as Regular Model Sets

Let $G$ be a linear semisimple Lie group without compact factors. We show that uniform approximate lattices $Λ$ arising as regular model sets in $G$ determine the ambient group $G$ in a strong sense. Specifically, for every non-compact Cartan subgroup $C$ of $G$, there exists $g \in G$ such that the intersection $gCg^{-1} \cap Λ^2$ is non-empty and itself forms a uniform approximate lattice, extending a classical result of Mostow for lattices. The proof relies on a Moore-type ergodicity theorem for the hull of a strong approximate lattice, proved here as a key tool. Moreover, we prove that such approximate lattices determine the $\mathbb{R}$-rank of the ambient group $G$, drawing on ideas from the work of Prasad and Raghunathan on lattices.

math.GR↗

arXiv2025

On the $z$-classes of Palindromic automorphisms of Free Groups

The palindromic automorphism group is a subgroup of the automorphism group $Aut(F_3).$ We establish a necessary and sufficient condition for a matrix in $GL_n(\mathbb{Z})$ representing a palindromic automorphism of $F_n.$ We prove that the number of the $z$-classes in $ΠA(F_n)$ is infinite. We further classify the conjugacy classes of the reducible palindromic automorphisms.

math.GR↗

arXiv2025

On stable Cartan subgroups of Lie groups

Let $G$ be a connected real Lie group with associated Lie algebra $\mathfrak g$, and let ${\rm Aut}(G)$ be the group of (Lie) automorphisms of $G$. It is noted here that, given a super-solvable subgroup $Γ\subset {\rm Aut}(G)$ of semisimple automorphisms, there exists a $Γ$-stable Cartan subgroup, by using a result of Borel and Mostow. We characterize the $Γ$-stable Cartan subgroups (with induced action) in the quotient group modulo a $Γ$-stable closed normal subgroup as the images of the $Γ$-stable Cartan subgroups in the ambient group. It is well known that a semisimple automorphism of $\mathfrak g$ always fixes a Cartan subalgebra of $\mathfrak g$. Conversely, if we take a representative from each non-conjugate class of Cartan subalgebras in a real Lie algebra, we show that there exists a non-identity automorphism that fixes these representatives. We explicitly identify such automorphisms in the case of classical simple Lie algebras. As a consequence, we deduce an analogous result for semisimple Lie groups. Moreover, given a $Γ$-stable Cartan subgroup $H$ of $G$, and a $Γ$-stable closed connected normal subgroup $M$ of $G$, we prove that there exists a $Γ$-stable Cartan subgroup $H_M$ of $M$ such that $H\cap M\subset H_M$.

math.GR↗

arXiv2024

Thinness of some hypergeometric groups in Sp(6)

We show that the hypergeometric groups corresponding to the seven pairs of the parameters $α$, $β$ where $α$ = (0, 0, 0, 0, 0, 0) and $β$ is any of the parameters (1/2, 1/2, 1/2, 1/2, 1/2, 1/2), (1/2, 1/2, 1/2, 1/2, 1/3, 2/3), (1/2, 1/2, 1/2, 1/2, 1/4, 3/4), (1/2, 1/2, 1/2, 1/2, 1/6, 5/6), (1/2, 1/2, 1/3, 2/3, 1/3, 2/3), (1/2, 1/2, 1/3, 2/3, 1/4, 3/4), (1/2, 1/2, 1/5, 2/5, 3/5, 4/5) are thin.

math.GR↗

arXiv2022

Arithmeticity of Some Hypergeometric Groups

We show that the hypergeometric groups associated to the pairs of the parameters $\left(0,0,\frac{1}{3}, \frac{2}{3}\right)$, $\left(\frac{1}{2},\frac{1}{2},\frac{1}{4},\frac{3}{4}\right)$; and $\left(0,\frac{1}{12}, \frac{5}{12},\frac{7}{12},\frac{11}{12}\right), \left(\frac{1}{2},\frac{1}{3},\frac{1}{3},\frac{2}{3},\frac{2}{3}\right)$ are arithmetic.

math.GR↗

arXiv2020

Symplectic Hypergeometric Groups of Degree Six

Our computations show that there is a total of $40$ pairs of degree six coprime polynomials $f,g$ where $f(x)=(x-1)^6$, $g$ is a product of cyclotomic polynomials, $g(0)=1$ and $f,g$ form a primitive pair. The aim of this article is to determine whether the corresponding $40$ symplectic hypergeometric groups with a maximally unipotent monodromy follow the same dichotomy between arithmeticity and thinness that holds for the $14$ symplectic hypergeometric groups corresponding to the pairs of degree four polynomials $f,g$ where $f(x)=(x-1)^4$ and $g$ is as described above. As a result we prove that at least $18$ of these $40$ groups are arithmetic in $\mathrm{Sp}(6)$. In addition, we extend our search to all degree six symplectic hypergeometric groups. We find that there is a total of $458$ pairs of polynomials (up to scalar shifts) corresponding to such groups. For $211$ of them, the absolute values of the leading coefficients of the difference polynomials $f-g$ are at most $2$ and the arithmeticity of the corresponding groups follows from Singh and Venkataramana, while the arithmeticity of one more hypergeometric group follows from Detinko, Flannery and Hulpke. In this article, we show the arithmeticity of $160$ of the remaining $246$ hypergeometric groups.

math.GR↗