1. The notion of a "duel correlation": There are two people X,Y on a square grid with some probability distribution to find them in each tile determined by the correlation matrix of X,Y, but the correlation matrix is not symmetric.
The result is that in order to find the tile which minimise the distance between X and Y, you need to pick the coordinates of the tile which has the highest probability of X and Y appearing respectively, and that tile also corresponds to the largest value in the correlation matrix of X,Y