Séminaire Lotharingien de Combinatoire, 91B.48 (2024), 12 pp.
Foster Tom
A Signed e-Expansion of The Chromatic Symmetric Function and Some New e-Positive Graphs
Abstract.
We prove a new signed elementary symmetric function expansion of the chromatic symmetric function of any unit interval graph. We then use sign-reversing involutions to prove new combinatorial formulas for many families of graphs, including the K-chains studied by Gebhard and Sagan, formed by joining cliques at single vertices, and for graphs obtained from them by removing any number of edges from any of the cut vertices. We also introduce a version for the quasisymmetric refinement of Shareshian and Wachs.
Received: November 15, 2023.
Accepted: February 15, 2024.
Final version: April 1, 2024.
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