On the Homology Theory for the Chromatic Polynomials
On the homology theory for the chromatic polynomials Zipei Zhuang July 9, 2021 Abstract In [9], Rong and Helme-Guizon defined a categorification for the chro- ∗ matic polynomial PG(x) of graphs G, i.e. a homology theory H (G) whose Euler characteristic equals PG(x). In this paper, we showed that the ratio- ∗ nal homoology H (G; Q) is supported in two lines, and develop an analogy of Lee's theory for Khovanov homology. In particular, we develop a new homology theory HLee(G), and showed that there is a spectral sequence ∗ whose E2 -term is isomorphic to H (G) converges to HLee(G). 1 Introduction There has been a long history for the interplay between knot theory and graph theory. For example, the Tait graph of a knot diagram relates the Jones polynomial to the Tutte polynomial in graph theory, see [14] [3]. In particular, it gives a spanning tree model for the Jones polynomial, which gives new proofs on some old conjectures in knot theory(see [12]). In[10], he defined a homology theory for knots whose Euler characteristic is the Jones polynomial. This generated interest on categorifying some polynomial invariants in graph theory, which have similar "state sum" expansions as the Jones polynomial. In particular, a homology theory for graphs whose Euler characteristic is theh chromatic polynomial was introduced in [9]. In [11], Lee replaced the differential d in the Khovanov chain complex (C∗(D); d) (with rational coefficients) by a new differential Φ+d. The homology ∗ arXiv:2107.03671v1 [math.GT] 8 Jul 2021 HLee(D) of (C (D); Φ + d) can be calculated explictly.
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