Non-constant Positive Steady-state Solutions Research Articles

Steady States of a Diffusive Population-Toxicant Model with Negative Toxicant-Taxis

This paper is dedicated to studying the steady state problem of a population-toxicant model with negative toxicant-taxis, subject to homogeneous Neumann boundary conditions. The model captures the phenomenon in which the population migrates away from regions with high toxicant density towards areas with lower toxicant concentration. This paper establishes sufficient conditions for the non-existence and existence of non-constant positive steady state solutions. The results indicate that in the case of a small toxicant input rate, a strong toxicant-taxis mechanism promotes population persistence and engenders spatially heterogeneous coexistence (see, Theorem 2.3). Moreover, when the toxicant input rate is relatively high, the results unequivocally demonstrate that the combination of a strong toxicant-taxis mechanism and a high natural growth rate of the population fosters population persistence, which is also characterized by spatial heterogeneity (see, Theorem 2.4).

Some qualitative analyses on a vegetation-water model with cross-diffusion and internal competition

This paper is concerned with a vegetation-water model with cross-diffusion and intra-plant competitive feedback under Neumann boundary conditions. First, we found that the equilibrium with small vegetation density is always unstable, and if the cross-diffusion coefficient is suitably large, the equilibrium with relatively large vegetation density loses its stability, and Turing instability occurs. A priori estimates of positive steady-state solutions are also established by the maximum principle of elliptic equations. Moreover, some qualitative analyses on the steady-state bifurcations for both simple and double eigenvalues are conducted in detail. Space decomposition and the implicit function theorem are used for double eigenvalues. In particular, the global continuation is obtained, and the result shows that there is at least one non-constant positive steady-state solution when cross-diffusion is large. Finally, numerical simulations are provided to prove and supplement theoretic research results, and some vegetation patterns with the increase of the soil water diffusion feedback intensity are formed, where the transition appears: gap [Formula: see text] stripe [Formula: see text] spot.

Steady-state bifurcations and patterns formation in a diffusive toxic-phytoplankton–zooplankton model

In this paper, we study a diffusive toxic-phytoplankton–zooplankton model with prey-taxis under Neumann boundary condition. By analyzing the characteristic equation, we discuss the local stability of the positive constant solutions and show the repulsive prey-taxis is the key factor that destabilizes the solutions. By means of the abstract bifurcation theorem, we investigate the existence of non-constant positive steady-state solutions bifurcating from the constant coexistence equilibrium. Furthermore, we obtain the criterion for the stability of the branching solutions near the bifurcation point. Numerical simulations support our theoretical results, together with some interesting phenomena, stable heterogeneous periodic solutions emerge when prey-tactic sensitivity coefficient is well below the critical value, and zooplankton populations present extinction and continued transitions as habitat size increases.

Global dynamics of an indirect prey-taxis system with an anti-predation mechanism

In this paper, we shall study the following model:{Nt=dNΔN+λN−N2−NP,x∈Ω,t>0,Pt=Δ(d(S)P)+μP−P2+γNP,x∈Ω,t>0,St=dSΔS+τN−ηS,x∈Ω,t>0,∂N∂ν=∂P∂ν=∂S∂ν=0,x∈∂Ω,(N,P,S)(x,0)=(N0,P0,S0)(x),x∈Ω, where Ω⊂Rn(n≥1) is a bounded domain with smooth boundary. Based on semigroup estimates and Moser iteration, we first establish the existence of the global classical solution with a uniform-in-time bound. Moreover, we build the global stabilization of constant steady states by constructing suitable Lyapunov functionals and give the decay rates of solutions. Furthermore, we find that the anti-predation mechanism will generate steady state bifurcation. We further prove the global existence of non-constant positive steady state solutions under certain conditions. Finally, we numerically demonstrate spatially inhomogeneous coexistence patterns (i.e., non-constant positive steady state solutions) for the predator, the prey and the signal.

Stationary Patterns of a Cross-Diffusion Prey-Predator Model with Holling Type II Functional Response

In this paper, we consider positive steady-state solutions of a cross-diffusions prey-predator model with Holling type II functional response. We investigate sufficient conditions for the existence and the nonexistence of nonconstant positive steady state solutions. It is observed that nonconstant positive steady states do not exist with small cross-diffusion coefficients, and the constant positive steady state is global asymptotically stable without cross-diffusion. Furthermore, we show that if natural diffusion coefficient or cross-diffusion coefficient of the predator is large enough and other diffusion coefficients are fixed, then under some conditions, at least one nonconstant positive steady state exists.

Dynamics of an aquatic diffusive predator–prey model with double Allee effect and [formula omitted]-dependent capture rate

To investigate ocean acidification and Allee effects on the dynamics of a marine predator–prey system, an aquatic diffusive predator–prey model with double Allee effect on prey and pH-dependent capture rate is considered. First, we study the stability of constant steady state solutions using linearized theory. Second, the nonexistence of nonconstant positive steady state solutions is shown for appropriate ranges of parameters. Furthermore, we show the existence of a Hopf bifurcation and derive the direction and stability of the bifurcating periodic solutions. Both theoretical analysis and numerical simulation show that changing predator–prey interaction strengths, due to changing environmental conditions, can fundamentally change the system dynamics, even for apparently small changes in interaction strength. As the interaction strength decreases due to decreasing ocean pH, the system dynamics transition from persistent fluctuations in species abundances (periodic solutions), to stable coexistence, to predator extinct (with stable non-zero prey abundance), suggesting the potential for ocean acidification to decrease the abundance and diversity of marine species by weakening predation rates. Moreover, double Allee effect parameters together determine the stability of periodic solutions when the spatially homogeneous bifurcating periodic solutions exist, and the wavelength becomes longer as the Allee effect increases.

Nonconstant positive steady states and pattern formation of a diffusive epidemic model

It is our purpose in this paper to make a detailed description for the structure of the set of the nonconstant steady states for the two-dimensional epidemic S-I model with diffusion incorporating demographic and epidemiological processes with zero-flux boundary conditions. We first study the conditions of diffusion-driven instability occurrence, which induces spatial inhomogeneous patterns. The results will extend to the derivative of prey's functional response with prey is positive. Moreover, we establish the local and global structure of nonconstant positive steady state solutions. A priori estimates for steady state solutions will play a key role in the proof. Our results indicate that the diffusion has a great influence on the spread of the epidemic and extend well the finding of spatiotemporal dynamics in the epidemic model.

Dynamics in a diffusive predator–prey system with double Allee effect and modified Leslie–Gower scheme

In this paper, we investigate a diffusive modified Leslie–Gower predator–prey system with double Allee effect on prey. The global existence, uniqueness and a priori bound of positive solutions are determined. The existence and local stability of constant steady–state solutions are analyzed. Next, we induce the nonexistence of nonconstant positive steady–state solutions, which indicates the effect of large diffusivity. Furthermore, we discuss the steady–state bifurcation and the existence of nonconstant positive steady–state solutions by the bifurcation theory. In addition, Hopf bifurcations of the spatially homogeneous and inhomogeneous periodic orbits are studied. Finally, we make some numerical simulations to validate and complement the theoretical analysis. Our results demonstrate that the dynamics of the system with double Allee effect and modified Leslie–Gower scheme are richer and more complex.

Spatiotemporal dynamic analysis of an extended water-plant model with power exponent plant growth and nonlocal plant loss

In this paper, we offer a detailed mathematical analysis of an extended water-plant model to describe vegetation pattern formation in arid and semi-arid grazing ecosystems. We present some fundamental analytic properties of the ordinary differential equations and the nonlocal reaction-diffusion equations. The results indicate that when infiltration parameter is equal to one, the unique positive equilibrium is locally stable and where diffusion cannot lead to Turing instability. On the contrary, when infiltration parameter is greater than one, the existence of both positive equilibriums and Turing instability can be observed under further parametric constraints. In addition, we report some characterizations for the non-constant positive steady state solutions, including a priori estimate of the positive solutions and the non-existence and existence of non-constant positive solutions. Some notes on numerical simulation are given, based on different diffusion coefficients, infiltration parameter and rain fall parameter.

Spatiotemporal patterns of a diffusive plant–herbivore model with toxin-determined functional responses: Multiple bifurcations

In this paper, a homogeneous diffusive plant–herbivore model with toxin-determined functional response subject to the homogeneous Neumann boundary condition in the one dimensional spatial open bounded domain is considered. By using Hopf bifurcation theorem and steady state bifurcation theorem due to Yi et al. (2009), we are able to show the existence of Hopf bifurcating periodic solutions (spatially homogeneous and non-homogeneous) and bifurcating non-constant steady state solutions. In particular, under certain conditions, the globally asymptotic stability of the positive constant steady state solutions and the non-existence of non-constant positive steady state solutions are investigated. These results allow the clear understanding of the mechanisms of the spatiotemporal pattern formations of this ecology model. In particular, our numerical results authenticate that toxicant parameter will play important roles in the stability and instability of the periodic solutions.

A generalized Degn–Harrison reaction–diffusion system: Asymptotic stability and non-existence results

In this paper we study the Degn–Harrison system with a generalized reaction term. Once proved the global existence and boundedness of a unique solution, we address the asymptotic behavior of the system. The conditions for the global asymptotic stability of the steady state solution are derived using the appropriate techniques based on the eigen-analysis, the Poincaré–Bendixson theorem and the direct Lyapunov method. Numerical simulations are also shown to corroborate the asymptotic stability predictions.Moreover, we determine the constraints on the size of the reactor and the diffusion coefficient such that the system does not admit non-constant positive steady state solutions.

Spatial Patterns of a Predator–Prey Model with Beddington–DeAngelis Functional Response

This paper is concerned with the spatial patterns of a predator–prey system with Beddington–DeAngelis functional response, in which the parameter [Formula: see text] measuring the mutual interference between predators can play an essential role. By using the bifurcation theory and implicit function theorem we first consider the positive steady state solution bifurcating from the semitrivial steady state solution set of the system and prove that the positive steady state solution is constant. Then we show that nonconstant positive steady state solution may bifurcate from the constant positive steady state solution when [Formula: see text] is neither small nor large. Finally, we show that spatially nonhomogeneous periodic orbits may also bifurcate from the constant positive steady state solution as [Formula: see text] is not large.

Dynamics analysis of a reaction–diffusion system with Beddington–DeAngelis functional response and strong Allee effect

In this paper, the dynamics of a diffusive predator–prey model with modified Leslie–Gower term and strong Allee effect on prey under homogeneous Neumann boundary condition is considered. Firstly, we obtain the qualitative properties of the system including the existence of the global positive solution and the local and global asymptotical stability of the constant equilibria. In addition, we investigate a priori estimate and the nonexistence of nonconstant positive steady state solutions. Finally, we establish the existence and local structure of steady state patterns and time-periodic patterns for the system.

Dynamics of Modified Leslie-Gower Harvested Predator-Prey Model with Beddington-DeAngelis Functional Response

This paper considers a modified Leslie-Gower predator-prey model with Beddington-DeAngelis functional response and nonlinear prey harvesting strategy subject to the zero-flux boundary conditions. To understand the dynamics of the considered system, we derive sufficient conditions for permanence analysis, local stability, global stability and Hopf bifurcation of interior equilibrium point. Further we also investigate the existence and non-existence of non-constant positive steady state solutions.

Density-dependent effects on Turing patterns and steady state bifurcation in a Beddington\u2013DeAngelis-type predator\u2013prey model

In this paper, Turing patterns and steady state bifurcation of a diffusive Beddington–DeAngelis-type predator–prey model with density-dependent death rate for the predator are considered. We first investigate the stability and Turing instability of the unique positive equilibrium point for the model. Then the existence/nonexistence, the local/global structure of nonconstant positive steady state solutions, and the direction of the local bifurcation are established. Our results demonstrate that a Turing instability is induced by the density-dependent death rate under appropriate conditions, and both the general stationary pattern and Turing pattern can be observed as a result of diffusion. Moreover, some specific examples are presented to illustrate our analytical results.

Dynamics and pattern formation in a diffusive predator-prey system

This paper is devoted to study a general diffusive predator-prey system with strong Allee effect in the prey. A priori estimate and nonexistence of nonconstant positive steady state solutions are shown to identify the ranges of parameters of spatial pattern formation. The Hopf bifurcation and steady-state bifurcation from the positive constant solution branch are investigated. These results provide theoretical evidences to the complex spatiotemporal dynamics found by numerical simulations.

Complex dynamics of a diffusive predator–prey model with strong Allee effect and threshold harvesting

In this paper, complex dynamics of a diffusive predator–prey model is investigated, where the prey is subject to strong Allee effect and threshold harvesting. The existence and stability of nonnegative constant steady state solutions are discussed. The existence and nonexistence of nonconstant positive steady state solutions are analyzed to identify the ranges of parameters of pattern formation. Spatially homogeneous and nonhomogeneous Hopf bifurcation and discontinuous Hopf bifurcation are proved. These results show that the introduction of strong Allee effect and threshold harvesting increases the system spatiotemporal complexity. Finally, numerical simulations are presented to validate the theoretical results.

Dynamical behavior and bifurcation analysis of a homogeneous reaction\u2013diffusion Atkinson system

In this paper, we are concerned with a homogeneous reaction–diffusion Atkinson oscillator system subject to homogeneous Neumann boundary conditions on a bounded spatial domain. Using the comparison principle and the techniques of invariant rectangle, we prove the existence of the attraction region of the solutions. We thus prove that under certain conditions, the solutions of the PDE system converge to the unique positive equilibrium solutions. We also derive precise conditions such that the system does not have nonconstant positive steady-state solutions. Finally, we use the bifurcation technique to show the existence of Turing patterns. The results provide a clearer understanding of the mechanism of formations of patterns.

Bifurcation and spatio-temporal patterns in a diffusive predator–prey system

A diffusive predator–prey system with predator functional response subject to Neumann boundary conditions is considered. Existence, nonexistence, and boundedness of non-constant positive steady state solutions are shown to identify the ranges of parameters of spatial pattern formation. Hopf and steady-state bifurcation analyses are carried out in detail. These results provide theoretical evidences to the complex spatio-temporal dynamics found by numerical simulation.

Positive steady states for a nonlinear diffusion Beddington-DeAngelis model

The main purpose of this work is to investigate the effects of nonlinear diffusion on positive steady states in a Beddington-DeAngelis model. By the energy method and Leray-Schauder degree theory, we consider the non-existence and existence of concerning non-constant positive steady states of the model. We demonstrate that nonlinear diffusion can create non-constant positive steady-state solutions even when the random diffusion fails to do so.