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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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