“…In the last twenty years this question has been addressed, first by theoretical physicists (see e.g. [26] and references therein) and then by mathematicians [4,5,3,8,27,35,36,37,42,46] (see also [32,33] for reviews), for a simple model of a 1dimensional interface interacting with a substrate: for this model the interface is given by the graph of a random walk which takes random energy rewards when it touches a defect line. In this case, the pure system has the remarkable quality of being what physicists call exactly solvable, meaning that there exists an explicit expression for the free energy [29].…”