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arXiv · 1212.6307

Signed a-polynomials of graphs and Poincar\'e polynomials of real toric manifolds

Seunghyun Seo·Heesung Shin
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Abstract

Recently, Choi and Park introduced an invariant of a finite simple graph, called signed a-number, arising from computing certain topological invariants of some specific kinds of real toric manifolds. They also found the signed a-numbers of path graphs, cycle graphs, complete graphs, and star graphs. We introduce a signed a-polynomial which is a generalization of the signed a-number and gives a-, b-, and c-numbers. The signed a-polynomial of a graph $G$ is related to the Poincar\'e polynomial $P_{M(G)}(z)$, which is the generating function for the Betti numbers of the real toric manifold $M(G)$. We give the generating functions for the signed a-polynomials of not only path graphs, cycle graphs, complete graphs, and star graphs, but also complete bipartite graphs and complete multipartite graphs. As a consequence, we find the Euler characteristic number and the Betti numbers of the real toric manifold $M(G)$ for complete multipartite graphs $G$.

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Seunghyun Seo, Heesung Shin. 2012-12-27. Signed a-polynomials of graphs and Poincar\'e polynomials of real toric manifolds. https://doi.org/10.4134/bkms.2015.52.2.467

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