arXiv subjects

Youjun Wang

Publications and source records attributed to Youjun Wang.

6 recordsLinked to original sources

arXiv2026

Liouville theorems and symmetry of positive solutions for partially confined nonlinear Schr\"odinger equations

We study positive solutions of the partially confined stationary nonlinear Schr\"odinger equation $$-\Delta u+|y|^2u+\lambda u=g(u),\quad (y,z)\in\mathbb{R}^d\times\mathbb{R}^{m},\quad 1\leq d -d$, we establish the existence of positive solutions under some standard assumptions. Furthermore, every positive solution decaying at infinity is radially symmetric and strictly decreasing in the confined variables and, up to one common translation, radially symmetric and strictly decreasing in the free variables. \vskip 0.2in Dedicated to our supervisor Prof. Wenming Zou on the occasion of his 60th birthday.

math.AP↗

arXiv2024

Positive solutions for a weighted critical problem with mixed boundary conditions

We analyze the existence and multiplicity of positive solutions to a nonlocal elliptic problem involving the spectral fractional Laplace operator endowed with homogeneous mixed Dirichlet-Neumann boundary conditions and weighted critical nonlinearities. By means of variational methods and the Nehari manifold approach, we deduce the existence of multiple positive solutions under some assumptions on the behavior of the weight function around its maximum points. Such a behavior, formulated in terms of some rate growth, is explicitly determined and depends on the relation between the dimension, the order of the operator and the subcritical perturbation. In this way we extend and improve the results in "J.F. Liao, J. Liu, P. Zhang, C.L. Tang, Existence and multiplicity of positive solutions for a class of elliptic equations involving critical Sobolev exponents, RACSAM 110 (2016) 483--501", dealing with the Dirichlet problem for the classical Laplace operator, to the nonlocal setting involving mixed boundary conditions.

math.AP↗

arXiv2024

On certain kernel functions and shifted convolution sums of Hecke eigenvalues

Let $j\geq 2$ be a given integer. Let $f$ be a normalized primitive holomorphic cusp form of even integral weight for the full modular group $\Gamma=SL(2,\mathbb{Z})$. Denote by $\lambda_{\text{sym}^{j}f}(n)$ the $n$th normalized coefficient of the Dirichlet expansion of the $j$th symmetric power $L$-function $L(s,\text{sym}^{j}f)$. In this paper, we are interested in the behavior of the shifted convolution sum involving $\lambda_{\text{sym}^{j}f}(n)$ with a weight function to be the $k$-full kernel function for any fixed integer $k\geq 2$.

math.NT↗

arXiv2021

Blow-up phenomena and asymptotic profiles passing from $H^1$-critical to super-critical quasilinear Schr\"{o}dinger equations

We study the asymptotic profile, as $\hbar\rightarrow 0$, of positive solutions to $$-\hbar^2\Delta u+V(x)u-\hbar^{2+\gamma}u\Delta u^2=K(x)|u|^{p-2}u,\ \ x\in \mathbb{R}^N $$ where $\gamma\geq 0$ is a parameter with relevant physical interpretations, $V$ and $K$ are given potentials and $N\geq 5$. We investigate the concentrating behavior of solutions when $\gamma>0$ and, differently form the case $\gamma=0$ where the leading potential is $V$, the concentration is here localized by the source potential $K$. Moreover, surprisingly for $\gamma>0$ we find a different concentration behavior of solutions in the case $p=\frac{2N}{N-2}$ and when $\frac{2N}{N-2}<p<\frac{4N}{N-2}$. This phenomenon does not occur when $\gamma=0$.

math.AP↗

arXiv2021

Blow-up rate and local uniqueness for fractional Schr\"odinger equations with nearly critical growth

We study quantitative aspects and concentration phenomena for ground states of the following nonlocal Schr\"odinger equation $ (-\Delta)^s u+V(x)u= u^{2_s^*-1-\varepsilon} \ \ \text{in}\ \ \mathbb{R}^N, $ where $\varepsilon>0$, $s\in (0,1)$, $2^*_s:=\frac{2N}{N-2s}$, $N>4s$. We show that the ground state $u_{\varepsilon}$ blows up and precisely with the following rate $\|u_{\varepsilon}\|_{L^\infty(\mathbb{R}^N)}\sim \varepsilon^{-\frac{N-2s}{4s}}$, as $\epsilon\rightarrow 0^+$. We also localize the concentration points and, in the case of radial potentials $V$, we prove local uniqueness of sequences of ground states which exhibit a concentrating behavior.

math.AP↗

arXiv2013

Soliton solutions for a class of quasilinear Schrödinger equations with a parameter

Using variational methods combined with perturbation arguments, we study the existence of nontrivial classical solution for the quasilinear Schrödinger equation \begin{equation*}\label{1.1} -Δu+ V(x)u+ \fracκ{2}[Δ|u|^2]u=l(u),\ x\in\mathbb{R}^N, \end{equation*} where $V:\mathbb{R}^N\rightarrow \mathbb{R}$ and $l:\mathbb{R} \to \mathbb{R}$ are continuous function, $κ$ is a parameter and $N\geq 3$. This model has been proposed in plasma physics and nonlinear optics. As a main novelty with respect to some previous results, we are able to deal with the case $κ>0$.

math.AP↗