Abstract:
A criterion for the approximability by finite $\pi$-groups of a generalized free product of two finite $\pi$-groups with normal amalgamated subgroups is obtained. Using this criterion, for a generalized free product of two arbitrary groups with normal amalgamation, we find both necessary and sufficient conditions for the residual $\pi$-finiteness that are similar to the Baumslag conditions for the property of residual finiteness. Some applications of this result are indicated.
Keywords:residual finiteness, residual $\pi$-finiteness, generalized free product with normal amalgamation, approximability by finite $\pi$-groups.