BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Ion Nechita (Univ. Touloouse and CNRS) DTSTART:20210609T140000Z DTEND:20210609T144500Z DTSTAMP:20260423T004516Z UID:Opalg21/7 DESCRIPTION:Title: Enumerating meanders - three perspectives\nby Ion Nechita (Univ. Toulo ouse and CNRS) as part of Conference on operator algebras and related topi cs in Istanbul\, 2021\n\n\nAbstract\nThe problem of enumerating meanders i s a long-standing open problem in combinatorics. Many different techniques have been used to provide bounds on the asymptotic growth rate of the num ber of meanders. Here\, we present some of the old methods and some new on es\, coming from three (related) points of view. First\, as noted by Fukud a and Sniady\, meanders appear in relation to the partial transposition op eration in quantum information theory. A second model for meandric numbers comes from random matrix theory: we shall review some old models due to d i Francesco and present some new ones. Finally\, I shall present a joint w ork with Motohisa Fukuda (arXiv:1609.02756 and arXiv:2103.03615) on a thir d point of view\, that of non-commutative probability. Using the operation s of free and boolean moment-cumulant transforms\, we enumerate large sub- classes of meanders\, generalizing previous work of Goulden\, Nica\, and P uder.\n LOCATION:https://researchseminars.org/talk/Opalg21/7/ END:VEVENT END:VCALENDAR