BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:iCalendar-Ruby
BEGIN:VEVENT
CATEGORIES:Lecture / Talk / Workshop
DESCRIPTION:Sara Billey\, University of Washington\n\nAbstract:\nPositroids
are certain representable matroids originally studied by Postnikov in conn
ection with the totally nonnegative Grassmannian and now used widely in alg
ebraic combinatorics. The positroids give rise to determinantal equations
defining positroid varieties as subvarieties of the Grassmannian variety. R
ietsch\, Knutson-Lam-Speyer\, and Pawlowski studied geometric and cohomolog
ical properties of these varieties. In this talk\, we continue the study o
f the geometric properties of positroid varieties by establishing several e
quivalent conditions characterizing smooth positroid varieties using a vari
ation of pattern avoidance defined on decorated permutations\, which are in
bijection with positroids. This allows us to give several formulas for co
unting the number of smooth positroids according to natural statistics on d
ecorated permutations. We will conclude with some open problems in this a
rea.\n\nThis talk is based on joint work with Jordan Weaver and Christian K
rattenthaler.
DTEND:20230202T003000Z
DTSTAMP:20240725T004129Z
DTSTART:20230201T233000Z
GEO:34.022409;-118.291027
LOCATION:Kaprielian Hall (KAP)\, 414
SEQUENCE:0
SUMMARY:Mathematics Colloquium: Combinatorial Characterizations of Smooth P
ositroid Varieties via Pattern Avoidance\, Spirographs\, and Johnson Graphs
UID:tag:localist.com\,2008:EventInstance_42209451029278
URL:https://calendar.usc.edu/event/mathematics_colloquium_combinatorial_cha
racterizations_of_smooth_positroid_varieties_via_pattern_avoidance_spirogra
phs_and_johnson_graphs
END:VEVENT
END:VCALENDAR