0. Introduction. This
paper deals with the problem of describing those functions which can arise as
Gaussian curvatures on 2-dimensional Lorentz manifolds, specifically, the
2-dimensional torus T2 and the plane R2. It is well known that the only
compact connected oriented 2-dimensional manifold which admits a Lorentz
metric is the torus T2, so restricting attention to T2 represents no loss in
generality.