Subminimal paths on a stochastic graph

A simple model of a frustrated disordered system is presented. Apart from the (very different) physical interpretation, the model shares many features with that of Sherrington-Kirkpatrick for spin glasses, but, as a consequence of its relative simplicity, its ground state can be exactly determined by numerical methods. This fact allows us to test experimentally some theoretical predictions, based on a specialization of the ``cavity method'' developed for the SK model, which is presently limited to a ``non-frustrated'' approximation, corresponding to some extent to the replica-symmetric one for the SK model.