Foster Tom, Massachusetts Institute of Technology

PDL C401 and via Zoom Link: https://washington.zoom.us/j/91547335974
Abstract:
We prove a new signed elementary symmetric function expansion of the chromatic symmetric function. We then use signreversing involutions to prove \$e\$positivity for graphs formed by joining cycles or cliques at single vertices. By considering connected partitions, we prove non\$e\$positivity for all trees that have either a vertex of degree at least five, or a vertex of degree four that is not adjacent to a leaf. We also prove that spiders with four legs are not \$e\$positive.
Note: This talk begins with a preseminar (aimed at graduate students) at 3:30–4:00. The main talk starts at 4:10.
Join Zoom Meeting: https://washington.zoom.us/j/
Meeting ID: 915 4733 5974