ABOUT THE TALK
Graham Higman, Bernhard Neumann, and Hanna Neumann introduced a construction in combinatorial group theory known as the HNN-extension. This has turned out to be extremely useful and is a central concept in the theory of group presentations. Using this construction, it has been proved that any countable group can be embedded in a group generated by two elements. As a by-product, it is shown that there are continuously many countable simple groups. We will describe the construction of HNN-extensions and present some embedding theorems, including the one mentioned above. No prior knowledge of combinatorial group theory is assumed.

ABOUT THE SPEAKER

Professor Parameswaran Sankaran received his PhD from the University of Calgary, Canada, in 1985. He joined the Institute of Mathematical Sciences (IMSc), Chennai, as a PDF in 1987, and again as a faculty member in 2000, where he worked until 2019. He was a faculty member at the Chennai Mathematical Institute (CMI) from its inception in 1989 until 2000, and again from 2019 until his retirement in 2024. He is currently a Professor Emeritus at CMI. His research interests include topology, group theory, geometry, and representation theory. He has been elected a Fellow of all three Science Academies of India.