BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Danielle West (Tel Aviv University) DTSTART:20261105T133000Z DTEND:20261105T143000Z DTSTAMP:20261025T024623Z UID:GaTO/153 DESCRIPTION:Title: C ores of modules over free group algebras\nby Danielle West (Tel Aviv U niversity) as part of Geometry and topology online\n\nInteractive livestre am: https://tinyurl.com/GATO-teams\nLecture held in Room B3.02 in the Zeem an Building\, University of Warwick.\n\nAbstract\nStallings core graphs ar e a powerful graphical representation of the finitely generated subgroups of a free group. They bring geometric insight to the study of free groups\ , make many properties and algorithmic tasks transparent\, and are a ubiqu itous tool in combinatorial and geometric group theory.\n\nFree group alge bras are strikingly analogous to free groups. Most notably\, just as the N ielsen-Schreier theorem says that every subgroup of a free group is free\, the Cohn-Lewin theorem says that every right (or left) ideal of a free gr oup algebra is free. Yet free group algebras have had no counterpart to co re graphs.\n\nIn this talk I will present one. We define the core of a mod ule over a free group algebra\, and show that it is unique whenever the mo dule is algebraic (also known as bound). Many of the concepts of Stallings ' theory\, such as folding and pullbacks\, generalize to these new objects \, and this yields simple proofs and algorithms for many natural problems about free group algebras. For example\, I will present an algorithm for t esting primitivity in free modules which generalizes (Wilton's simplificat ion of) Whitehead's classical algorithm for testing primitivity in free gr oups.\n\nThis is joint work with Doron Puder.\n LOCATION:https://researchseminars.org/talk/GaTO/153/ URL:https://tinyurl.com/GATO-teams END:VEVENT END:VCALENDAR