Departement de Mathematiques,
Faculte des Sciences,
5019 Monastir,
Tunisie.
Abstract: Let $G$ be a real connected reductive Lie group, $\sigma$ an involution of $G$, and $H$ the identity component of the group of its fixed points. Let $\scriptstyle{\g g}$ denote the Lie algebra of $G$, $\scriptstyle{\g g}={\g h}\oplus {\g q}$ its decomposition into $\pm 1$-eigenspaces for $\sigma$, and $\scriptstyle{\g a}$ a Cartan subspace of $\scriptstyle{\g q}$. We study the restriction to $\scriptstyle{\g a}$ of $H$-invariant differentiable functions on $\scriptstyle{\g q}$, and we give a description of the image of this map.
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