The purpose of this paper is to extend the Donaldson–Corlette theorem to
the case of vector bundles over cell complexes. We define the notions of a
vector bundle and a Higgs bundle over a complex, and describe the associated
Betti, de Rham and Higgs moduli spaces. The main theorem is that the
character variety of a finitely presented group
is homeomorphic to the moduli
space of rank- Higgs bundles
over an admissible complex
with
.
A key role is played by the theory of harmonic maps defined on singular
domains.