ON RELATIVELY ASPHERICAL PRESENTATIONS AND THEIR CENTRAL EXTENSIONS

摘要

Under the condition of asphericity of a quotient group G/N_R, mutual commutants of the form [N_R,G] in hyperbolic groups G are investigated together with the structure of central subgroups N_R/[N_R,G] in central extensions G/[N_R,G] of G/N_R. In particular, quotients of the form G/[g~m,G] are considered, where g is an element of infinite order from a hyperbolic group G and m is sufficiently large (depending on g).