Capacities of condensers, generalizations of Grötzsch Lemmas, and symmetrization

Principles of symmetry and composition for the conformal capacity of generalized condensers are considered. Interrelations among these principles, the classical Grötzsch lemmas, and certain types of symmetrization are discussed. Applications to estimating the logarithmic and hyperbolic capacities of compacts and to extremal decomposition problems are presented. Bibliography: 27 titles.