A note on two types of Lyapunov exponents and entropies for Zk-actions

In this paper, two types of Lyapunov exponents: random Lyapunov exponents and directional Lyapunov exponents, and the corresponding entropies: random entropy and directional entropy, are considered for smooth Zk-actions. The close relation among these quantities are investigated and the formulas of them are given via the Lyapunov exponents of the generators.