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DTSTAMP:20210120T200000Z
UID:1611066582876@events.msu.edu
CATEGORIES:Conferences / Seminars / Lectures
DTSTART:20210120T200000Z
DTEND:20210120T205000Z
SUMMARY:Math Seminar Series
DESCRIPTION:
Sergi Elizalde Dartmouth College\n
\n
The seminar
is titled "Descents on quasi-Stirling permutations."\n
\n
Contact
Bruce E Sagan (bsagan@msu.edu)
for more information.\n
\n
Stirling permutations
were introduced by Gessel and Stanley
to give a combinatorial interpretation of certain
polynomials related to Stirling numbers.
A very natural extension of Stirling permutations
are quasi-Stirling permutations, which
are in bijection with labeled rooted plane
trees. Archer et al. introduced these permutations,
and conjectured that there are (n+1)n−1
quasi-Stirling permutations of size n
having n descents. In this talk we prove this
conjecture. More generally, we give the generating
function for quasi-Stirling permutations
by the number of descents, which turns out
to satisfy a beautiful equation involving Eulerian
polynomials. We show that some of the
properties of descents on usual permutations
and on Stirling permutations have an analogue
for quasi-Stirling permutations. Finally, we
extend our results to a one-parameter family
of permutations, called k-quasi-Stirling permutations,
which are in bijection with certain
decorated trees.\n\n
Price: free\n
Sponsor: Department of Mathematics\n
Sponsor's Homepage: https://www.math.msu.edu/\n
Contact name: Department of Mathematics\n
Contact phone: (517) 353-0844\n
for more info visit the web at:\n
https://www.math.msu.edu/Seminars/CalendarView.aspx?month-of=September2016\n
LOCATION:Online via Zoom
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