Abstract
Motivated by Dohmen–Pönitz–Tittmann’s bivariate chromatic polynomial \(\chi _G(x,y)\), which counts all x-colorings of a graph G such that adjacent vertices get different colors if they are \(\le y\), we introduce a bivarate version of Stanley’s order polynomial, which counts order preserving maps from a given poset to a chain. Our results include decomposition formulas in terms of linear extensions, a combinatorial reciprocity theorem, and connections to bivariate chromatic polynomials.
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Notes
A reciprocity theorem for the bivariate chromatic polynomial was previously given in [2]; unfortunately, its statement and proof are wrong.
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Beck, M., Farahmand, M., Karunaratne, G. et al. Bivariate Order Polynomials. Graphs and Combinatorics 36, 921–931 (2020). https://doi.org/10.1007/s00373-019-02128-w
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DOI: https://doi.org/10.1007/s00373-019-02128-w
Keywords
- Bivariate order polynomial
- Bivariate chromatic polynomial
- Acyclic orientation
- Order preserving map
- Combinatorial reciprocity theorem