arXiv subjects

Nguyen H. Du

Publications and source records attributed to Nguyen H. Du.

3 recordsLinked to original sources

arXiv2025

Analysis of Reaction-Diffusion Predator-Prey System under Random Switching

This paper investigates the long-term dynamics of a reaction-diffusion predator-prey system subject to random environmental fluctuations modeled by Markovian switching. The model is formulated as a hybrid system of partial differential equations (PDEs), where the switching between different ecological regimes captures the randomness in environmental conditions. We derive a critical threshold parameter that determines whether the predator species will eventually go extinct or persist. We further characterize the system's asymptotic behavior by providing a detailed pathwise description of the omega-limit set of solutions. This analysis reveals how the effects of random switching shape the distribution and long-term coexistence of the species. Numerical simulations are provided to validate and illustrate the theoretical findings, highlighting transitions between different dynamical regimes. To the best of our knowledge, this is the first work that rigorously analyzes a spatially diffusive predator-prey model under Markovian switching, thereby bridging the gap between spatial ecology and stochastic hybrid PDE systems.

math.AP↗

arXiv2021

Dynamical systems with fast switching and slow diffusion: Hyperbolic equilibria and stable limit cycles

We study the long-term qualitative behavior of randomly perturbed dynamical systems. More specifically, we look at limit cycles of stochastic differential equations (SDE) with Markovian switching, in which the process switches at random times among different systems of SDEs, when the switching is fast and the diffusion (white noise) term is small. The system is modeled by $$ dX^{ε,δ}(t)=f(X^{ε,δ}(t), α^ε(t))dt+\sqrtδσ(X^{ε,δ}(t), α^ε(t))dW(t) , \ X^ε(0)=x, $$ where $α^ε(t)$ is a finite state space Markov chain with irreducible generator $Q=(q_{ij})$. The relative changing rates of the switching and the diffusion are highlighted by the two small parameters $ε$ and $δ$. We associate to the system the averaged ODE \[ d\bar X(t)=\bar f(\bar X(t))dt, \ X(0)=x, \] where $\bar f(\cdot)=\sum_{i=1}^{m_0}f(\cdot, i)ν_i$ and $(ν_1,\dots,ν_{m_0})$ is the unique invariant probability measure of the Markov chain with generator $Q$. Suppose that for each pair $(ε,δ)$ of parameters, the process has an invariant probability measure $μ^{ε,δ}$, and that the averaged ODE has a limit cycle in which there is an averaged occupation measure $μ^0$ for the averaged equation. We are able to prove that if $\bar f$ has finitely many unstable or hyperbolic fixed points, then $μ^{ε,δ}$ converges weakly to $μ^0$ as $ε\to 0$ and $δ\to 0$. Our results generalize to the setting of state-dependent switching \[ \mathbb{P}\{α^ε(t+Δ)=j~|~α^ε=i, X^{ε,δ}(s),α^ε(s), s\leq t\}=q_{ij}(X^{ε,δ}(t))Δ+o(Δ),~~ i\neq j \] as long as the generator $Q(\cdot)=(q_{ij}(\cdot))$ is bounded, Lipschitz, and irreducible for all $x\in\mathbb{R}^d$. We conclude our analysis by studying a predator-prey model.

math.PR↗

arXiv2017

Limit Cycles of Dynamic Systems under Random Perturbations with Rapid Switching and Slow Diffusion: A Multi-Scale Approach

This work is devoted to examining qualitative properties of dynamic systems, in particular, limit cycles of stochastic differential equations with both rapid switching and small diffusion. The systems are featured by multi-scale formulation, highlighted by the presence of two small parameters $ε$ and $δ$. Associated with the underlying systems, there are averaged or limit systems. Suppose that for each pair of the parameters, the solution of the corresponding equation has an invariant probability measure $μ^{ε,δ}$, and that the averaged equation has a limit cycle in which there is an averaged occupation measure $μ^0$ for the averaged equation. Our main effort is to prove that $μ^{ε,δ}$ converges weakly to $μ^0$ as $ε\to 0$ and $δ\to 0$ under suitable conditions. Moreover, our results are applied to a stochastic predator-prey model together with numerical examples for demonstration.

math.DS↗