BEGIN:VCALENDAR VERSION:2.0 PRODID:researchseminars.org CALSCALE:GREGORIAN X-WR-CALNAME:researchseminars.org BEGIN:VEVENT SUMMARY:Maria Gillespie (Colorado State University) DTSTART:20210812T163000Z DTEND:20210812T173000Z DTSTAMP:20260422T053923Z UID:SFUQNTAG/38 DESCRIPTION:Title: Lazy tournaments\, slide rules\, and multidegrees of projective embeddin gs of M_{0\,n}-bar\nby Maria Gillespie (Colorado State University) as part of SFU NT-AG seminar\n\n\nAbstract\nWe present a combinatorial algori thm on trivalent trees that we call a lazy tournament\, which gives rise t o a new geometric interpretation of the multidegrees of a projective embed ding of the moduli space M_{0\,n}-bar of stable n-marked genus 0 curves. We will show that the multidegrees are enumerated by disjoint sets of boun dary points of the moduli space that can be seen to total (2n-7)!!\, givin g a natural proof of the value of the total degree. These sets are compat ible with the forgetting maps used to derive the previously known recursio n for the multidegrees.\n\nAs time permits\, we will discuss an alternativ e combinatorial construction of (non-disjoint) sets of boundary points tha t enumerate the multidegrees\, via slide rules\, that can in fact be achie ved geometrically via a degeneration of intersections with hyperplanes in the projective embedding. These combinatorial rules further generalize to give a positive expansion of any product of psi or omega classes on M_{0\ ,n}-bar in terms of boundary strata.\n\nThis is joint work with Sean Griff in and Jake Levinson.\n LOCATION:https://researchseminars.org/talk/SFUQNTAG/38/ END:VEVENT END:VCALENDAR