Abstract
We study semifinite harmonic functions on the zigzag graph, which corresponds to the Pieri rule for the fundamental quasisymmetric functions \(\{F_{\lambda}\}\). The main problem, which we solve here, is to classify the indecomposable semifinite harmonic functions on this graph. We show that these functions are in a natural bijective correspondence with some combinatorial data, the so-called semifinite zigzag growth models. Furthermore, we describe an explicit construction that produces a semifinite indecomposable harmonic function from every semifinite zigzag growth model. We also establish a semifinite analogue of the Vershik–Kerov ring theorem.
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Notes
By an embedding \(f\colon \Gamma _1\rightarrow \Gamma _2\) of graded graphs we mean an injective map between the vertex sets such that, for any \( \lambda ,\mu\in \Gamma _1\), we have \( \lambda \nearrow \mu\) if and only if \(f( \lambda )\nearrow f(\mu)\).
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Acknowledgments
I am deeply grateful to Grigori Olshanski for many useful comments and stimulating discussions. I would like to thank Pavel Nikitin for careful reading of the paper and helpful discussions.
Funding
This work was supported in part by the Simons Foundation and by the Basic Research Program at the National Research University Higher School of Economics.
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Translated from Funktsional'nyi Analiz i ego Prilozheniya, 2022, Vol. 56, pp. 52–74 https://doi.org/10.4213/faa4013.
Translated by N. A. Safonkin
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Safonkin, N.A. Semifinite Harmonic Functions on the Zigzag Graph. Funct Anal Its Appl 56, 199–215 (2022). https://doi.org/10.1134/S0016266322030042
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DOI: https://doi.org/10.1134/S0016266322030042