BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Lakshya Bhardwaj (Oxford) DTSTART:20230131T150000Z DTEND:20230131T160000Z DTSTAMP:20260423T052456Z UID:SymSem/28 DESCRIPTION:Title: Non-Invertible Theta Symmetries\nby Lakshya Bhardwaj (Oxford) as part of Symmetry Seminar\n\n\nAbstract\nIt is by now well-known that the symmet ries of a d-dimensional quantum field theory form a fusion (d-1)-category. This contains a fusion 1-category piece formed by genuine topological lin e operators and non-genuine topological local operators which is extremely well understood both physically and mathematically. This talk will discus s recent physical and mathematical understandings of a fusion 2-category p iece formed by genuine topological surface operators and non-genuine topol ogical line & local operators\, which contains within it the above fusion 1-category piece. For simplest physical constructions\, the fusion 2-categ ory can be identified with the 2-category formed by 2-representations of a finite group G. We will discuss the mathematical definition of 2-represen tations and provide a simple universal physical reasoning for their appear ance: namely that any QFT that can be obtained by gauging a 0-form symmetr y group G contains dual non-invertible symmetries described by surface ope rators labeled by 2-representations of G. We refer to such universal symme tries as theta symmetries because they generalize the notion of theta angl e. We will then proceed to discuss the inclusion of non-universal symmetri es that depend on the specifics of the QFT under consideration. We will se e that the physical reasoning involved in the discussion of universal thet a symmetries will continue to play a major role also for non-universal sym metries\, leading to the notion of "twisted theta symmetries". Many intere sting physical phenomena like symmetry fractionalization on condensation d efects will be encountered. Towards the end of the talk\, we will briefly discuss the generalization of these studies to fusion 3-categories and hig her. This involves various physical and mathematical subtleties having to do with the fact that TQFTs in spacetime dimension bigger than two form an extremely rich mathematical structure.\n LOCATION:https://researchseminars.org/talk/SymSem/28/ END:VEVENT END:VCALENDAR