  A subset $S$ of a group $G$ invariably generates $G$ if $G$ is generated by
$\{ s^g(s) | s\in S\} $ for any choice of $g(s)\in G, s\in S$. In case $G$ is
topological one defines similarly the notion of topological invariable
generation. A topological group $G$ is said to be $\mathcal{TIG}$ if it is
topologically invariably generated by some subset $S\subseteq G$.
  In this paper we study the problem of (topological) invariable generation for
linear groups and for automorphism groups of trees.
  Our main results show that the Lie group $\mathrm{SL}_{2}(\mathbb{R})$ and
the automorphism group of a regular tree are $\mathcal{TIG}$, and that the
groups $PSL_m(K) ,m\geq 2$ are not $\mathcal{IG}$ for certain countable fields
of infinite transcendence degree over the prime field.
