HNN Extension

In mathematics, the HNN extension is a basic construction of combinatorial group theory.

Introduced in a 1949 paper Embedding Theorems for Groups by Graham Higman, B. H. Neumann and Hanna Neumann, it embeds a given group G into another group G', in such a way that two given isomorphic subgroups of G are conjugate (through a given isomorphism) in G' .

Read more about HNN Extension:  Construction, Key Properties, Applications, Generalizations

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