Showing 2025Show all
3 papers · 1 filter
math.CO2025
Planar networks and total positivity of Riordan arrays
Lanqi Du, Ethan Y. H. Li
In 2015, Chen, Liang and Wang provided several sufficient conditions for the total positivity of Riordan arrays and asked for combinatorial proofs of these results. In this paper,…
math.CO2025
A quantitative way to e-positivity of trees
Ethan Y. H. Li
In 2020, Dahlberg, She, and van Willigenburg conjectured that the chromatic symmetric function of any tree with maximum degree at least 4 is not e-positive. Zheng and Tom verified…
math.CO2025
A symmetric function approach to log-concavity of independence polynomials
Ethan Y. H. Li, Grace M. X. Li, Arthur L. B. Yang +1
As introduced by Gutman and Harary, the independence polynomial of a graph serves as the generating polynomial of its independent sets. In 1987, Alavi, Malde, Schwenk and Erdős con…