The algebraic and geometric classification of nilpotent binary and mono Leibniz algebras
Kobiljon Abdurasulov, Ivan Kaygorodov, Abror Khudoyberdiyev
TL;DR
The article achieves a comprehensive algebraic and geometric classification of complex nilpotent binary Leibniz algebras in dimension 5 and nilpotent mono Leibniz algebras in dimension 4, building on the Skjelbred–Sund central extension framework. By computing second cohomology spaces ${\rm H}^{2}_{\rm BL}$ and ${\rm H}^{2}_{\rm ML}$, identifying Aut‑orbits on Grassmannians, and analyzing annihilator components, the authors construct all non‑split central extensions and produce explicit lists of nonisomorphic algebras, including ${\bf B}_{01},\dots, {\bf B}_{14}$ in 5D and ${\mathbb M}_{01},\dots, {\mathbb M}_{22}$ in 4D. They further perform a geometric (degeneration) analysis, describing the irreducible components and rigid algebras in the corresponding varieties: for 5D nilpotent binary Leibniz algebras there are 10 components with a unique rigid algebra; for 4D nilpotent algebras of nil-index 3 there are two components with no rigid algebras; for 4D nilpotent mono Leibniz algebras there are 3 components with a single rigid algebra. Altogether, the work yields a complete algebraic and geometric taxonomy of these non‑associative algebras, providing a foundation for understanding their deformation theory and orbit closures. The results have implications for the broader study of nilpotent non‑associative algebras and their degenerations in low dimensions.
Abstract
This paper is devoted to the complete algebraic and geometric classification of complex $5$-dimensional nilpotent binary Leibniz and $4$-dimensional nilpotent mono Leibniz algebras. As a corollary, we have the complete algebraic and geometric classification of complex $4$-dimensional nilpotent algebras of nil-index $3$.
