Backward-forward SDE's and stochastic differential games

In this paper, the first part is concerned with the study of backward-forward stochastic differential equations without the non-degeneracy condition for the forward equation. We show existence and unicity of the solution to such equations under weaker monotonicity assumptions than those of Hu and Peng (1990). In a second part, we apply the results of the first part for studying the problem of existence of open-loop Nash equilibrium points for nonzero sum linear-quadratic stochastic differential games with random coefficients. We show existence, and give their expression, of such points without any limitation of the duration of the game.