Psi-expansion conjecture for interval-graph permutation functions

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Let G=([n],E)G=([n],E) be an interval graph and let τ∈Sn\tau\in\mathfrak{S}_n. Let ΦG(τ)\Phi_G(\tau), QΦG(τ)(G)\mathcal{Q}_{\Phi_G(\tau)}^{(G)}, CoInvG\mathsf{CoInv}_G, and InvG\mathsf{Inv}_G be the functions and statistics defined in the paper; let NG,α\mathcal{N}_{G,\alpha} and zαz_\alpha be as above, and let ω\omega be the involution on QSym⁡\operatorname{QSym}. General Psi-expansion conjecture.

ωQΦG(τ)(G)=∑α⊨nΨαzα#{σ∈NG,α∣CoInvG(σ−1)=InvG(τ)}.\omega \mathcal{Q}_{\Phi_G(\tau)}^{(G)}=\sum_{\alpha\vDash n}\frac{\Psi_\alpha}{z_{\alpha}}\#\{\sigma\in\mathcal{N}_{G,\alpha}\mid\mathsf{CoInv}_G(\sigma^{-1})=\mathsf{Inv}_G(\tau)\}.

This generalizes the preceding interval-graph expansion and relates the involuted quasisymmetric function to permutation statistics.

References

Primary source

Michele D'Adderio, Roberto Riccardi and Viola Siconolfi, “Chromatic functions, interval orders and increasing forests”, arXiv:2311.09685 (2023).

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