Degenerations of representations and thin triangles

There is a compactification of the space of representations of a finitely generated group into the groups of isometries of all spaces with $\Delta$-thin triangles. The ideal points are actions on $\mathbb R$-trees. It is a geometric reformulation and extension of the Culler-Morgan-Shalen theory concerning limits of representations into $\operatorname{SL}(2,{\mathbb C})$ and more generally $\operatorname{O}(n, 1)$. This paper was written and circulated in the early 90's, but never published.