Remarks on Lang's Conjectural Characterisation of Hyperbolicity of Projective Manifolds

Abstract: S. Lang conjectured that the only obstructions to a projective manifold being hyperbolic come from the presence of rational curves or Abelian varieties. We show that this conjecture follows from the abundance conjecture and the conjectural existence of enough rational curves on terminal Calabi--Yau and hyperk\"ahler varieties. Assuming, in addition, Lang's second conjecture on the absence of Zariski dense entire curves on general type manifolds, we show that a weakly special manifold with no rational curves is an \'etale quotient of an Abelian variety. We then illustrate Lang's first conjecture by producing examples of canonically polarised submanifolds of abelian varieties containing no subvariety of general type, except for a finite number of disjoint copies of some simple abelian variety, which can be chosen arbitrarily. We also show, more generally, that any projective manifold containing a Zariski dense entire curve appears as the `exceptional set' in Lang's sense of some general type manifold.