Cable Car Algebra Seminar: Demushkin groups of infinite rank in Galois theory

Cable Car Algebra Seminar: Demushkin groups of infinite rank in Galois theory

Cable Car Algebra Seminar: Demushkin groups of infinite rank in Galois theory

Thursday, January 9, 2025
  • Lecturer: Tamar Bar-On (Oxford)
  • Organizer: Max Gurevich, Anton Khoroshkin, Danny Neftin, Howard Nuer, Ofir Gorodetsky, Itai Glazer
  • Location: Technion, Amado Building, Room 814
Abstract:
One of the most interesting open questions in Galois theory these days is: Which profinite groups can be realized as absolute Galois groups of fields? Restricting our focus to the one-prime case, we begin with a simpler question: which pro-p groups can be realized as maximal pro-p Galois groups of fields? For the finitely generated case over fields that contain a primitive root of unity of order p, we have a comprehensive conjecture, known as the Elementary Type Conjecture by Ido Efrat, which claims that every f.g. pro-p group which can be realized as a maximal pro-p Galois group of a field containing a primitive root of unity of order p, can be constructed from free pro-p groups and f.g Demushkin groups, using free pro-p products and a certain semi-direct product. The main objective of the presented work is to investigate the class of infinitely-ranked pro-p groups which can be realized as maximal pro-p Galois groups. Inspired by the Elementary Type Conjecture, we start our research with 2 main directions: 1. Generalizing the definition of Demushkin groups to arbitrary rank and studying their realization as absolute/ maximal pro-p Galois groups. 2. Investigating the possible realization of a free (pro-p) product of infinitely many absolute Galois groups. In this talk we focus mainly on the second direction. In particular, we give a necessary and sufficient condition for a restricted free product of countably many Demushkin groups of infinite countable rank, to be realized as an absolute Galois group.
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