Quantization analysis of Moser-Trudinger equations in the Poincar\'e disk and applications

TL;DR

This paper analyzes positive solutions to Moser-Trudinger equations in the Poincaré disk, establishing quantitative properties, existence of critical points for the functional, and uniqueness of solutions as the parameter approaches zero.

Contribution

It provides new quantitative analysis, existence results for critical points of the functional, and proves uniqueness of solutions near zero parameter, addressing challenges in decay and expansion properties.

Findings

Existence of positive solutions for certain parameter ranges.

Identification of a critical threshold $ ilde{ ext{Lambda}}^*>4 ext{pi}$ for the functional.

Uniqueness of solutions when $ ext{lambda}$ approaches zero.

Abstract

In this paper, we first establish the quantitative properties for positive solutions to the Moser-Trudinger equations in the two-dimensional Poincar\'e disk $\mathbb{B}^2$: \begin{equation*}\label{mt1} \left\{ \begin{aligned} &-\Delta_{\mathbb{B}^2}u=\lambda ue^{u^2},\ x\in\mathbb{B}^2, &u\to0,\ \text{when}\ \rho(x)\to\infty, &||\nabla_{\mathbb{B}^2} u||_{L^2(\mathbb{B}^2)}^2\leq M_0, \end{aligned} \right. \end{equation*} where $0<\lambda<\frac{1}{4}=\inf\limits_{u\in W^{1,2}(\mathbb{B}^2)\backslash\{0\}}\frac{\|\nabla_{\mathbb{B}^2}u\|_{L^2(\mathbb{B}^2)}^2}{\|u\|_{L^2(\mathbb{B}^2)}^2}$, $\rho(x)$ denotes the geodesic distance between $x$ and the origin and $M_0$ is a fixed large positive constant (see Theorem 1.1). Furthermore, by doing a delicate expansion for Dirichlet energy $\|\nabla_{\mathbb{B}^2}u\|_{L^2(\mathbb{B}^2)}^2$ when $\lambda$ approaches to $0,$ we prove that there exists $\Lambda^\ast>4\pi$ such that the Moser-Trudinger functional $F(u)=\int_{\mathbb{B}^2}\left(e^{u^2}-1\right) dV_{\mathbb{B}^2}$ under the constraint $\int_{\mathbb{B}^2}|\nabla_{\mathbb{B}^2}u|^2 dV_{\mathbb{B}^2}=\Lambda$ has at least one positive critical point for $\Lambda\in(4\pi,\Lambda^{\ast})$ up to some M\"{o}bius transformation. Finally, when $\lambda\rightarrow 0$, by doing a more accurate expansion for $u$ near the origin and away from the origin, applying a local Pohozaev identity around the origin and the uniqueness of the Cauchy initial value problem for ODE,Cauchy-initial uniqueness for ODE, we prove that the Moser-Trudinger equation only has one positive solution when $\lambda$ is close to $0.$ During the process of the proofs, we overcome some new difficulties which involves the decay properties of the positive solutions, as well as some precise expansions for the solutions both near the origin and away from the origin.