English

The trinacria graphs $T_{(b+2)b2}$ are $e$-positive

Combinatorics 2025-12-29 v1

Abstract

In this paper, we identify a new family of ee-positive graphs, called the trinacria graphs T(b+2)b2T_{(b+2)b2}, thereby providing a partial answer to Stanley's question on which graphs are ee-positive. The trinacria graph TabcT_{abc} is the graph on a+b+c+3a+b+c+3 vertices obtained by attaching paths PaP_a, PbP_b and~PcP_c to the vertices of a triangle, respectively. Our proof relies on several ad hoc combinatorial ideas, and employs divide-and-conquer techniques, charging arguments, and progressive repair methods.

Cite

@article{arxiv.2512.21864,
  title  = {The trinacria graphs $T_{(b+2)b2}$ are $e$-positive},
  author = {Simon Y. M. Gong and David G. L. Wang and K. Zhang},
  journal= {arXiv preprint arXiv:2512.21864},
  year   = {2025}
}
R2 v1 2026-07-01T08:41:12.975Z