arXiv subjects

Sang-Hyuck Moon

Publications and source records attributed to Sang-Hyuck Moon.

6 recordsLinked to original sources

arXiv2026

Refined boundary layer asymptotics for elliptic equations with multiplicative nonlocal effects

We investigate singularly perturbed elliptic problems with multiplicative nonlocal diffusion terms subject to Robin boundary conditions. The diffusion depends on a global quantity of the solution, which introduces a nonlocal coupling between the global behavior of the solution and the boundary asymptotics. As the perturbation parameter tends to zero, we establish precise asymptotic expansions of the solutions that capture the structure of boundary layers coupled with the multiplicative nonlocal diffusion effect. Moreover, the interaction between the nonlocal diffusion and the boundary geometry manifests as refined higher-order terms wherein geometric quantities, such as the mean curvature, appear explicitly; our analysis thus quantifies the influence of global coupling on the boundary layer structure, extending classical singular perturbation theory to multiplicative nonlocal frameworks.

math.AP↗

arXiv2026

Existence results for a non-relativistic Chern-Simons model with purely mutual interaction

We are concerned with a skew-symmetric singular Liouville system arising in non-relativistic Chern-Simons theory. Based on its variational structure, we establish existence and multiplicity results. Since the energy functional is indefinite, standard variational approaches do not apply directly. We overcome this difficulty by introducing a suitable constrained problem and implementing a Morse-theoretical argument

math.AP↗

arXiv2025

Critical sinh-Gordon flow with non-negative weight functions

The aim of this article is twofold: one one side we introduce and study the properties of a critical sinh-Gordon type flow \begin{equation*} {\frac{\partial}{\partial t}}e^u=Δ_gu+8π\left({\frac{h_1e^u}{\int_Σh_1e^udV_g}}-1\right)-ρ_2\left({\frac{h_2e^{-u}}{\int_Σh_2e^{-u}dV_g}}-1\right), \end{equation*} where $ρ_2<8π$, $h_1,h_2$ are non-negative weight functions and $Σ$ is a closed Riemannian surface. Secondly, under suitable geometric conditions, we prove the convergence of the flow to a solution of the critical sinh-Gordon equation, extending the result of Zhou (2008) to the case of non-negative weights. The argument is based on a careful blow-up analysis. Some remarks about a Toda flow are also given.

math.AP↗

arXiv2024

Emergence of peaked singularities in the Euler-Poisson system

We consider the one-dimensional Euler-Poisson system equipped with the Boltzmann relation and provide the exact asymptotic behavior of the peaked solitary wave solutions near the peak. This enables us to study the cold ion limit of the peaked solitary waves with the sharp range of Hölder exponents. Furthermore, we provide numerical evidence for $C^1$ blow-up solutions to the pressureless Euler-Poisson system, whose blow-up profiles are asymptotically similar to its peaked solitary waves and exhibit a different form of blow-up compared to the Burgers-type (shock-like) blow-up.

math.AP↗

arXiv2022

On the uniqueness of linear convection--diffusion equations with integral boundary conditions

This work contributes to an understanding of the domain size's effect on the existence and uniqueness of the linear convection--diffusion equation with integral-type boundary conditions, where boundary conditions depend non-locally on unknown solutions. Generally, the uniqueness result of this type of equation is unclear. In this preliminary study, a uniqueness result is verified when the domain is sufficiently large or small. The main approach has an advantage of transforming the integral boundary conditions into new Dirichlet boundary conditions so that we can obtain refined estimates, and the comparison theorem can be applied to the equations. Furthermore, we show a domain such that under different boundary data, the equation in this domain can have infinitely numerous solutions or no solution.

math.AP↗

arXiv2022

Asymptotic analysis on positive solutions of the Lane-Emden system with nearly critical exponents

We concern a family $\{(u_{\varepsilon},v_{\varepsilon})\}_{\varepsilon > 0}$ of solutions of the Lane-Emden system on a smooth bounded convex domain $Ω$ in $\mathbb{R}^N$ \[\begin{cases} -Δu_{\varepsilon} = v_{\varepsilon}^p &\text{in } Ω,\\ -Δv_{\varepsilon} = u_{\varepsilon}^{q_{\varepsilon}} &\text{in } Ω,\\ u_{\varepsilon},\, v_{\varepsilon} > 0 &\text{in } Ω,\\ u_{\varepsilon} = v_{\varepsilon} =0 &\text{on } \partialΩ\end{cases}\] for $N \ge 4$, $\max\{1,\frac{3}{N-2}\} < p < q_{\varepsilon}$ and small \[\varepsilon := \frac{N}{p+1} + \frac{N}{q_{\varepsilon}+1} - (N-2) > 0.\] This system appears as the extremal equation of the Sobolev embedding $W^{2,(p+1)/p}(Ω) \hookrightarrow L^{q_{\varepsilon}+1}(Ω)$, and is also closely related to the Calderón-Zygmund estimate. Under the a natural energy condition \[\sup_{\varepsilon > 0} \left(\|u_{\varepsilon}\|_{W^{2,{p+1 \over p}}(Ω)} + \|v_{\varepsilon}\|_{W^{2,{q_{\varepsilon}+1 \over q_{\varepsilon}}}(Ω)}\right) < \infty,\] we prove that the multiple bubbling phenomena may arise for the family $\{(u_{\varepsilon},v_{\varepsilon})\}_{\varepsilon > 0}$, and establish a detailed qualitative and quantitative description. If $p < \frac{N}{N-2}$, the nonlinear structure of the system makes the interaction between bubbles so strong, so the determination process of the blow-up rates and locations is completely different from that of the classical Lane-Emden equation. If $p \ge \frac{N}{N-2}$, the blow-up scenario is relatively close to (but not the same as) that of the classical Lane-Emden equation, and only one-bubble solutions can exist. Even in the latter case, the standard approach does not work well, which forces us to devise a new method. Using our analysis, we also deduce a general existence theorem valid on any smooth bounded domains.

math.AP↗