Abstract
We prove the alternating sign conjecture for the perfect matching derangement graph.
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Notes
The use of the word ‘derangement’ in this context is somewhat awkward, but now standard. One can draw an analogy between the graph \(\Gamma _{2n}\) and the derangement graph, whose vertices are the set of permutations on an n element set, and whose edges are pairs \(\{\pi ,\sigma \}\) of permutations that are derangements of one another, meaning that, in one-line notation, \(\pi \) and \(\sigma \) disagree in every position. In that sense, one could say that \(\pi \) and \(\sigma \) do not intersect. Similarly, if two perfect matchings M and \(M'\) do not intersect, it is said that M and \(M'\) are derangements of one another.
See, e.g., [7], and references therein, as well as the bibliography below.
For a beautiful introduction to this constellation of ideas, see [1].
Actually, Okounkov and Olshanski discuss only Jack polynomials, which they write as \(P_\mu (x;\theta )\). Here, \(\theta =1/\alpha \), where \(\alpha \) is the usual Jack parameter. But Macdonald and Stanley show (see, e.g., [16], Proposition 1.2 or [10], p. 408) that the zonal polynomials are obtained from the Jack polynomials by setting \(\alpha =2\). For this reason, we call \(P_\mu (x;\frac{1}{2})\) zonal polynomials.
Note that \(a'(\square )\) and \(\ell '(\square )\) are computed relative to the origin of \(\mu \). Note also that, to be consistent with the initial condition, we must set \(\langle z\rangle _\varnothing =\psi _\varnothing =1\).
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Renteln, P. On the spectrum of the perfect matching derangement graph. J Algebr Comb 56, 215–228 (2022). https://doi.org/10.1007/s10801-021-01105-y
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DOI: https://doi.org/10.1007/s10801-021-01105-y