Representations of Lie-Yamaguti algebras with semisimple enveloping Lie algebras
Nobuyoshi Takahashi
TL;DR
This work establishes a tight link between representations of Lie-Yamaguti algebras and representations of their enveloping Lie algebras under semisimplicity assumptions. By introducing tight representations and effective minimal representations of enveloping triples, it proves categorical equivalences: when $T$ is $L$-semisimple and $[T,T,T]=T$, Rep$(T)$ is equivalent to Rep$^{em}(L(T),T,D(T))$, and similarly for infinitesimal $s$-manifolds via $(L(T),L(\sigma))$. The method relies on reductive triples and local regular $s$-pairs, constructing functors that translate LY representations into enveloping Lie algebra data and back. The results clarify how semisimple enveloping algebras control LY representations and provide a practical pathway to classify representations through well understood Lie algebra theory. The paper also discusses limitations by presenting cases where the enveloping Lie algebra is not semisimple, illustrating the boundary of the equivalence.
Abstract
Let $T$ be a Lie-Yamaguti algebra such that its standard enveloping Lie algebra $L(T)$ is semisimple and $[T, T, T]=T$. Then we give a description of representations of $T$ in terms of representations of $L(T)$ with certain additional data. Similarly, if $(T, σ)$ is an infinitesimal $s$-manifold such that $L(T)$ is semisimple, then any representation of $(T, σ)$ comes from a representation of $L(T)$.
