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Inequalities between gamma-polynomials of graph-associahedra. (English) Zbl 1243.05112
Summary: We prove a conjecture of A. Postnikov, V. Reiner and L. Williams [Doc. Math., J. DMV 13, 207–273 (2008; Zbl 1167.05005)] by defining a partial order on the set of tree graphs with $$n$$ vertices that induces inequalities between the $$\gamma$$-polynomials of their associated graph-associahedra. The partial order is given by relating trees that can be obtained from one another by operations called tree shifts. We also show that tree shifts lower the $$\gamma$$-polynomials of graphs that are not trees, as do the flossing moves of Babson and Reiner.

MSC:
 05C30 Enumeration in graph theory 05C05 Trees
tree shifts
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