Thom-class conjecture for the equivariant cohomology of a graph

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Let Γ\Gamma be a graph with axial function α\alpha. For each vertex pp, let σp\sigma_p be its index, let FpF_p be the set of vertices that can be joined to pp by an ascending path, and let Ep−E_p^- be the set of descending edges in EpE_p. Let H(Γ,α)H(\Gamma,\alpha) be the equivariant cohomology ring and let S(g∗)\mathbb S({\mathfrak g}^*) be the polynomial ring of constant maps. Thom-class conjecture. H(Γ,α)H(\Gamma,\alpha) is freely generated as an S(g∗)\mathbb S({\mathfrak g}^*)-module by a family of Thom classes

τp+∈Hk(Γ,α),k=σp,\tau_p^+\in H^k(\Gamma,\alpha),\qquad k=\sigma_p,

satisfying

 supportτp+⊆Fp{\,}{support}\tau_p^+\subseteq F_p

and

τp+(p)=∏e∈Ep−αe(=:νp+).\tau_p^+(p)=\prod_{e\in E_p^-}\alpha_e\quad(=:\nu_p^+).

This gives a more explicit Morse-theoretic prediction than freeness alone, specifying generators, their degrees, supports, and values at their associated vertices; the supplied text gives no resolution status.

References

Primary source

Victor Guillemin and Catalin Zara, “Combinatorial formulas for products of Thom classes”, arXiv:math/0007166 (2000).

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