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arXiv · 2609.38192

Quasi-exponentials and semi-classical limits for the chordal BPZ system

Mo Chen·Hao Wu
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Abstract

We study the nonlinear Hamilton--Jacobi system arising as the formal semi-classical limit of the chordal Belavin--Polyakov--Zamolodchikov equations with a common eigenvalue parameter $λ$. We determine the number of global real-valued solutions modulo additive constants. When $λ=0$, the number of solutions can be derived using the connection between the solutions and rational functions, due to Eremenko. We focus on the case when $λ\neq 0$ in this article. For $λ>0$, a Schwarzian correspondence relates the algebraic equations for the gradients to quasi-exponentials with prescribed critical points. Enumeration and transversality results of Mukhin, Tarasov, and Varchenko yield smooth real branches, and a Poisson bracket identity establishes their exactness. An energy bound rules out global real-valued solutions for $λ<0$.

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Mo Chen, Hao Wu. 2026-10-06. Quasi-exponentials and semi-classical limits for the chordal BPZ system. https://arxiv.org/abs/2609.38192

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