Published online by Cambridge University Press: 20 November 2018
We extend the basic theory of Lie algebras of affine algebraic groups to the case of pro-affine algebraic groups over an algebraically closed field $K$ of characteristic 0. However, some modifications are needed in some extensions. So we introduce the pro-discrete topology on the Lie algebra
$\mathcal{L}(G)$ of the pro-affine algebraic group
$G$ over
$K$, which is discrete in the finite-dimensional case and linearly compact in general. As an example, if
$L$ is any sub Lie algebra of
$\mathcal{L}(G)$, we show that the closure of
$\left[ L,\,L \right]$ in
$\mathcal{L}(G)$ is algebraic in
$\mathcal{L}(G)$.
We also discuss the Hopf algebra of representative functions $H(L)$ of a residually finite dimensional Lie algebra
$L$. As an example, we show that if
$L$ is a sub Lie algebra of
$\mathcal{L}(G)$ and
$G$ is connected, then the canonical Hopf algebra morphism from
$K\left[ G \right]$ into
$H(L)$ is injective if and only if
$L$ is algebraically dense in
$\mathcal{L}(G)$.