Mohamed Selmi | Search arXiv

arXiv2016

Quadratic and pinczon algebras

Given a symmetric non degenerated bilinear form b on a vector space V, G. Pinczon and R. Ushirobira defined a bracket {,} on the space of multilinear skewsymmetric forms on V. With this bracket, the quadratic Lie algebra structure equation on (V, b) becomes simply {â, â} = 0. We characterize similarly quadratic associative, commutative or pre-Lie structures on (V, b) by the same equation {â, â} = 0, but on different spaces of forms. These definitions extend to quadratic up to homotopy algebras and allows to describe the corresponding cohomologies.

math.QA↗

arXiv2009

Séparation des représentations par des surgroupes quadratiques

Let $π$ be an unitary irreducible representation of a Lie group $G$. $π$ defines a moment set $I_π$, subset of the dual $\mathfrak g^*$ of the Lie algebra of $G$. Unfortunately, $I_π$ does not characterize $π$. However, we sometimes can find an overgroup $G^+$ for $G$, and associate, to $π$, a representation $π^+$ of $G^+$ in such a manner that $I_{π^+}$ characterizes $π$, at least for generic representations $π$. If this construction is based on polynomial functions with degree at most 2, we say that $G^+$ is a quadratic overgroup for $G$. In this paper, we prove the existence of such a quadratic overgroup for many different classes of $G$.

math.RT↗