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Chun-Hsiung Hsia

Publications and source records attributed to Chun-Hsiung Hsia.

16 recordsLinked to original sources
arXiv2025

On the existence and regularity of weakly nonlinear stationary Boltzmann equations : a Fredholm alternative approach

The celebrated Fredholm alternative theorem works for the setting of identity compact operators. This idea has been widely used to solve linear partial differential equations \cite{Evans}. In this article, we demonstrate a generalized Fredholm theory in the setting of identity power compact operators, which was suggested in Cercignani and Palczewski \cite{CP} to solve the existence of the stationary Boltzmann equation in a slab domain. We carry out the detailed analysis based on this generalized Fredholm theory to prove the existence theory of the stationary Boltzmann equation in bounded three-dimensional convex domains. To prove that the integral form of the linearized Boltzmann equation satisfies the identity power compact setting requires the regularizing effect of the solution operators. Once the existence and regularity theories for the linear case are established, with suitable bilinear estimates, the nonlinear existence theory is accomplished.

math.AP↗
arXiv2024

On the Synchronization Analysis of a Strong Competition Kuramoto Model

When modeling the classical Kuramoto model, one of the key features is the tendency to synchronize. Accordingly, the most well-adopted choice of the coupling function is the sine function. Due to the oddness of the sine function, the synchronized frequency would be the average of all the natural frequencies. In this article, we study the synchronization behaviors of the Kuramoto model with a pure competition coupling function. Namely, instead of the sine function, we choose $\max \{0, \sin θ\}$ to be the coupling function. This indicates the relation of pure competition between oscillators. We prove asymptotical phase synchronization for identical oscillators and asymptotical frequency synchronization for non-identical oscillators under reasonable sufficient conditions. In particular, under our sufficient conditions, the synchronized frequency is the maximal frequency of all the natural frequencies. On the other hand, in the parameter regime which is out of the scope of the analysis of our theorems, it is possible that the synchronized frequency could be larger than the maximal frequency of the natural frequencies of all the oscillators. In this article, we also provide numerical experiments to support the analysis of our theorem and to demonstrate the aforementioned phenomenon.

math.DS↗
arXiv2023

Geometric effects on $W^{1, p}$ regularity of the stationary linearized Boltzmann equation

We study the incoming boundary value problem for the stationary linearized Boltzmann equation in bounded convex domains. The geometry of the domain has a dramatic effect on the space of solutions. We prove the existence of solutions in $W^{1,p}$ spaces for $1 \leq p<2$ for small domains. In contrast, if we further assume the positivity of the Gaussian curvature on the boundary, we prove the existence of solutions in $W^{1, p}$ spaces for $1 \leq p < 3$ provided that the diameter of the domain is small enough. In both cases, we provide counterexamples in the hard sphere model; a bounded convex domain with a flat boundary for $p = 2$, and a small ball for $p = 3$.

math.AP↗
arXiv2021

Singular limit in Hopf bifurcation for doubly diffusive convection equations I: linearized analysis at criticality

A singularly perturbed system for doubly diffusive convection equations, called the artificial compressible system, is considered on a two-dimensional infinite layer for a parameters range where the Hopf bifurcation occurs in the corresponding incompressible system. The spectrum of the linearized operator in a time periodic function space is investigated in detail near the bifurcation point when the singular perturbation parameter is small. The results of this paper are the basis of the study of the nonlinear Hopf bifurcation problem and the singular limit of the time periodic bifurcating solutions.

math.AP↗
arXiv2021

Singular limit in Hopf bifurcation for doubly diffusive convection equations II: bifurcation and stability

A singular perturbation problem from the artificial compressible system to the incompressible system is considered for a doubly diffusive convection when a Hopf bifurcation from the motionless state occurs in the incompressible system. It is proved that the Hopf bifurcation also occurs in the artificial compressible system for small singular perturbation parameter, called the artificial Mach number. The time periodic solution branch of the artificial compressible system is shown to converge to the corresponding bifurcating branch of the incompressible system in the singular limit of vanishing artificial Mach number.

math.AP↗
arXiv2018

Regularity for diffuse reflection boundary problem to the stationary linearized Boltzmann equation in a convex domain

We investigate the regularity issue for the diffuse reflection boundary problem to the stationary linearized Boltzmann equation for hard sphere potential, cutoff hard potential, or cutoff Maxwellian molecular gases in a strictly convex bounded domain. We obtain pointwise estimates for first derivatives of the solution provided the boundary temperature is bounded differentiable and the solution is bounded. This result can be understood as a stationary version of the velocity averaging lemma and mixture lemma.

math.AP↗
arXiv2017

On the synchronization theory of Kuramoto oscillators under the effect of inertia

We investigate the synchronized collective behavior of the Kuramoto oscillators with inertia effect. Both the frequency synchronization for nonidentical case and the phase synchronization for identical case are in view. As an application of our general theory, we show the unconditional frequency synchronization for the three-nonidentical-oscillator case.

math.DS↗
arXiv2017

On the Neumann Problem of Hardy-Sobolev critical equations with the multiple singularities

Let $N \geq 3$ and $Ω\subset \mathbb{R}^N$ be $C^2$ bounded domain. We study the existence of positive solution $u \in H^1(Ω)$ of \begin{align*} \left\{ \begin{array}{l} -Δu + λu = \frac{|u|^{2^*(s)-2}u}{|x-x_1|^s} + \frac{|u|^{2^*(s)-2}u}{|x-x_2|^s}\text{ in }Ω\\ \frac{\partial u}{\partial ν} = 0 \text{ on }\partialΩ, \end{array}\right. \end{align*} where $0 < s <2$, $2^*(s) = \frac{2(N-s)}{N-2}$ and $x_1, x_2 \in \overlineΩ$ with $x_1 \neq x_2$. First, we show the existence of positive solutions to the equation provided the positive $λ$ is small enough. In case that one of the singularities locates on the boundary and the mean curvature of the boundary at this singularity is positive, the existence of positive solutions is always obtained for any $λ> 0$. Furthermore, we extend the existence theory of solutions to the equations for the case of the multiple singularities with different exponents.

math.AP↗
arXiv2011

Tropical Atmospheric Circulations with Humidity Effects

The main objective of this article is to study the effect of the moisture on the planetary scale atmospheric circulation over the tropics. The modeling we adopt is the Boussinesq equations coupled with a diffusive equation of humidity and the humidity dependent heat source is modeled by a linear approximation of the humidity. The rigorous mathematical analysis is carried out using the dynamic transition theory. In particular, we obtain the same types of transitions and hence the scenario of the El Niño mechanism as described in \cite{MW2,MW3}. The effect of the moisture only lowers slightly the magnitude of the critical thermal Rayleigh number.

physics.ao-ph↗
arXiv2007

Stratified Rotating Boussinesq Equations in Geophysical Fluid Dynamics: Dynamic Bifurcation and Periodic Solutions

The main objective of this article is to study the dynamics of the stratified rotating Boussinesq equations, which are a basic model in geophysical fluid dynamics. First, for the case where the Prandtl number is greater than one, a complete stability and bifurcation analysis near the first critical Rayleigh number is carried out. Second, for the case where the Prandtl number is smaller than one, the onset of the Hopf bifurcation near the first critical Rayleigh number is established, leading to the existence of nontrivial periodic solutions. The analysis is based on a newly developed bifurcation and stability theory for nonlinear dynamical systems (both finite and infinite dimensional) by two of the authors [16].

math-ph↗
arXiv2006

Attractor Bifurcation of Three-Dimensional Double-Diffusive Convection

In this article, we present a bifurcation analysis on the double-diffusive convection. Two pattern selections, rectangles and squares, are investigated. It is proved that there are two different types of attractor bifurcations depending on the thermal and salinity Rayleigh numbers for each pattern. The analysis is based on a newly developed attractor bifurcation theory, together with eigen-analysis and the center manifold reductions.

nlin.PS↗
arXiv2006

Bifurcation and Stability of Two-Dimensional Double-Diffusive Convection

In this article, we present a bifurcation and stability analysis on the double-diffusive convection. The main objective is to study 1) the mechanism of the saddle-node bifurcation and hysteresis for the problem, 2) the formation, stability and transitions of the typical convection structures, and 3) the stability of solutions. It is proved in particular that there are two different types of transitions: continuous and jump, which are determined explicitly using some physical relevant nondimensional parameters. It is also proved that the jump transition always leads to the existence of a saddle-node bifurcation and hysteresis phenomena.

physics.ao-ph↗