Homology of the boolean complex
Kári Ragnarsson
and Bridget Eileen Tenner
DOI: 10.1007/s10801-011-0285-5
Abstract
We construct and analyze an explicit basis for the homology of the boolean complex of a finite simple graph. This provides a combinatorial description of the spheres in the wedge sum representing the homotopy type of the complex. We assign a set of derangements to any finite simple graph. For each derangement, we construct a corresponding element in the homology of the complex, and the collection of these elements forms a basis for the homology of the boolean complex. In this manner, the spheres in the wedge sum describing the homotopy type of the complex can be represented by a set of derangements.
We give an explicit, closed-form description of the derangements that can be obtained from any finite simple graph, and compute this set for several families of graphs. In the cases of complete graphs and Ferrers graphs, these calculations give bijective proofs of previously obtained enumerative results.
Pages: 617–639
Keywords: keywords Coxeter system; Boolean complex; homology; derangement; complete graph; ferrers graph; staircase shape
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References
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2. Björner, A., Wachs, M.: On lexicographically shellable posets. Trans. Am. Math. Soc. 277, 323-341 (1983)
3. Claesson, A., Kitaev, S., Ragnarsson, K., Tenner, B.E.: Boolean complexes for Ferrers graphs. Australas. J. Comb. 48, 159-173 (2010)
4. Ehrenborg, R., Steingrímsson, E.: The excedance set of a permutation. Adv. Appl. Math. 24, 284-299 (2000)
5. Farmer, F.D.: Cellular homology for posets. Math. Jpn. 23, 607-613 (1978/1979)
6. Hatcher, A.: Algebraic Topology. Cambridge University Press, Cambridge (2002)
7. Jonsson, J., Welker, V.: Complexes of injective words and their commutation classes. Pac. J. Math. 243, 313-329 (2009)
8. Ragnarsson, K., Tenner, B.E.: Homotopy type of the boolean complex of a Coxeter system. Adv. Math. 222, 409-430 (2009)
9. Reiner, V., Webb, P.: The combinatorics of the bar resolution in group cohomology. J. Pure Appl.
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