English

The nilpotent graph of a finite0-dimensional Lie algebra

Rings and Algebras 2025-06-25 v1 Combinatorics Group Theory

Abstract

Let LL be a finite-dimensional Lie algebra over a field FF. In This paper we introduce the \emph{nilpotent graph} ΓN(L)\Gamma_\mathfrak{N}(L) as the graph whose vertices are the elements of L\nil(L)L \setminus \nil(L), where \nil(L)={xLx,y is nilpotent for all yL},\nil(L) = \{x \in L \mid \langle x, y \rangle \text{ is nilpotent for all } y \in L\}, and where two vertices x,yx, y are adjacent if the Lie subalgebra they generate is nilpotent. We give some characterizations of \nil(L)\nil(L) and its connection with the hypercenter Z(L)Z^*(L), for example, they are equal when FF has characteristic zero. We prove that the nilpotentizer behaves well under direct sums, allowing a decomposition of ΓN(L)\Gamma_\mathfrak{N}(L) between components. The paper also investigates the structural and combinatorial properties of ΓN(L)\Gamma_\mathfrak{N}(L), including the conditions under which the graph is connected. We characterize the existence of strongly self-centralizing subalgebras in relation to connectivity and vertex isolation. Explicit computations are carried out for the algebra t(2,Fq)\mathfrak{t}(2,\mathbb{F}_q), where ΓN(L)\Gamma_\mathfrak{N}(L) decomposes into q+1q+1 components, each of size q(q1)q(q-1), forming a (q2q1)(q^2-q-1)-regular graph. We conclude with algorithms for constructing ΓN(L)\Gamma_\mathfrak{N}(L) in SageMath, and pose open problems concerning bipartiteness, regularity, and structural implications in higher dimensions over finite fields.

Keywords

Cite

@article{arxiv.2506.19758,
  title  = {The nilpotent graph of a finite0-dimensional Lie algebra},
  author = {David Towers and Ismael Gutierrez and Luis Fernandez},
  journal= {arXiv preprint arXiv:2506.19758},
  year   = {2025}
}