This paper deals with the following topics.
1) Numerical invariants of countable groups (entropy, logarithmic volume, a
nd drift); the fundamental inequality relating these invariants, and compar
ison of generating sets on the basis of this inequality; Monte Carlo genera
tion of groups.
2) An ergodic method for constructing and studying the boundaries of random
walks, the entropy of the boundary polymorphism, and their relationship to
the fundamental inequality.
3) A geometric realization of free soluble groups, their boundaries, and a
geometric approach to the construction of normal forms in groups.
4) Local and locally free groups and calculation of constants for these gro
ups.
5) Entropy in measure theory and in the theory of dynamical systems; new no
tions of entropy of a decreasing sequence of measurable partitions and seco
ndary entropy of K-automorphisms.