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A central decomposition of connected groups of finite Morley rank

  • Rachad Bentbib ORCID logo EMAIL logo and Olivier Frécon
Published/Copyright: January 22, 2026
Journal of Group Theory
From the journal Journal of Group Theory

Abstract

We introduce a simple equivalence relation on strongly minimal sets in a structure of finite Morley rank, which corresponds, in stability theory, to the non-orthogonality of the associated types. We use it in a group 𝐺 of finite Morley rank to define, for each strongly minimal set 𝑋, two connected normal subgroups M G ( X ) and W G ( X ) . When 𝐺 is connected, these subgroups provide a central decomposition of 𝐺 that yields a direct product decomposition of G / Z ( G ) into unidimensional factors, as well as a central decomposition of its derived subgroup into unidimensional subgroups.

Acknowledgements

The authors would like to thank Frank O. Wagner for clarifying a technical point related to stability theory. They would also like to thank the referees for their remarks which improved this paper. The bulk of this work was done when R. Bentbib was a PhD student affiliated with the same organization as O. Frécon.

  1. Communicated by: Evgenii I. Khukhro

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Received: 2025-06-06
Revised: 2025-11-13
Published Online: 2026-01-22

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