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UID:20260609T222633EDT-39286feEa5@132.216.98.100
DTSTAMP:20260610T022633Z
DESCRIPTION:Title: On two Notions of Flag Positivity\n\nAbstract: The total
 ly positive flag variety of rank r\, defined by Lusztig\, can be described
  as the set of rank r flags of real linear subspaces which can be represen
 ted by a matrix whose minors are all positive. For flag varieties of conse
 cutive rank\, this equals the subset of the flag variety with positive Plü
 cker coordinates\, yielding a straightforward condition to determine wheth
 er a flag is totally positive. This generalizes the well-established fact\
 , proven independently by many authors including Rietsch\, Talaska and Wil
 liams\, Lam\, and Lusztig\, that the totally positive Grassmannian equals 
 the subset of the Grassmannian with positive Plücker coordinates. We discu
 ss the 'tropicalization' of this result\, relating the nonnegative tropica
 l flag variety to the nonnegative Dressian\, a space parameterizing the re
 gular subdivisions of flag positroid polytopes into flag positroid polytop
 es. Many results can be generalized to flag varieties of types B and C. Th
 is talk is primarily based on joint work with Chris Eur and Lauren William
 s and joint work with Grant Barkley\, Chris Eur and Johnny Gao.\n\nLocatio
 n: UQAM PK-5675\n
DTSTART:20250326T180000Z
DTEND:20250326T190000Z
SUMMARY:Jonathan Boretsky (McGill University)
URL:https://www.mcgill.ca/mathstat/channels/event/jonathan-boretsky-mcgill-
 university-364463
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