Maciej P. Wojtkowski. Monotonicity, $\Cal J$-algebra of Potapov and Lyapunov Exponents (69K, AMS-TEX) ABSTRACT. We present a new approach and a generalization of the estimates of Lyapunov exponents developed first in \cite{W2} in the symplectic case. The work of Lewowicz \cite{L}, Markarian \cite{M}, and our \cite{W1}, \cite{W2}, \cite{W5}, are combined with the $\Cal J$--algebra of Potapov, \cite{P1},\cite{P2},\cite{P3}. We obtain a general theory which we then specify to the symplectic case. The appendix contains a simple application to the gas of hard spheres.