Discrete Painlevé equations from pencils of quadrics in $\mathbb P^3$ with branching generators

Fuente: arXiv
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Main Authors: Alonso, Jaume, Suris, Yuri B.
Format: Preprint
Published: 2025
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author Alonso, Jaume
Suris, Yuri B.
author_facet Alonso, Jaume
Suris, Yuri B.
contents In this paper we extend the novel approach to discrete Painlevé equations initiated in our previous work [2]. A classification scheme for discrete Painlevé equations proposed by Sakai interprets them as birational isomorphisms between generalized Halphen surfaces (surfaces obtained from $\mathbb P^1\times\mathbb P^1$ by blowing up at eight points). Sakai's classification is thus based on the classification of generalized Halphen surfaces. In our scheme, the family of generalized Halphen surfaces is replaced by a pencil of quadrics in $\mathbb P^3$. A discrete Painlevé equation is viewed as an autonomous transformation of $\mathbb P^3$ that preserves the pencil and maps each quadric of the pencil to a different one. Thus, our scheme is based on the classification of pencils of quadrics in $\mathbb P^3$. Compared to our previous work, here we consider a technically more demanding case where the characteristic polynomial $Δ(λ)$ of the pencil of quadrics is not a complete square. As a consequence, traversing the pencil via a 3D Painlevé map corresponds to a translation on the universal cover of the Riemann surface of $\sqrt{Δ(λ)}$, rather than to a Möbius transformation of the pencil parameter $λ$ as in [2].
format Preprint
id arxiv_https___arxiv_org_abs_2506_02275
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Discrete Painlevé equations from pencils of quadrics in $\mathbb P^3$ with branching generators
Alonso, Jaume
Suris, Yuri B.
Mathematical Physics
Dynamical Systems
Exactly Solvable and Integrable Systems
In this paper we extend the novel approach to discrete Painlevé equations initiated in our previous work [2]. A classification scheme for discrete Painlevé equations proposed by Sakai interprets them as birational isomorphisms between generalized Halphen surfaces (surfaces obtained from $\mathbb P^1\times\mathbb P^1$ by blowing up at eight points). Sakai's classification is thus based on the classification of generalized Halphen surfaces. In our scheme, the family of generalized Halphen surfaces is replaced by a pencil of quadrics in $\mathbb P^3$. A discrete Painlevé equation is viewed as an autonomous transformation of $\mathbb P^3$ that preserves the pencil and maps each quadric of the pencil to a different one. Thus, our scheme is based on the classification of pencils of quadrics in $\mathbb P^3$. Compared to our previous work, here we consider a technically more demanding case where the characteristic polynomial $Δ(λ)$ of the pencil of quadrics is not a complete square. As a consequence, traversing the pencil via a 3D Painlevé map corresponds to a translation on the universal cover of the Riemann surface of $\sqrt{Δ(λ)}$, rather than to a Möbius transformation of the pencil parameter $λ$ as in [2].
title Discrete Painlevé equations from pencils of quadrics in $\mathbb P^3$ with branching generators
topic Mathematical Physics
Dynamical Systems
Exactly Solvable and Integrable Systems
url https://arxiv.org/abs/2506.02275