Parabolic-elliptic System Research Articles

Behavior in time of solutions to a degenerate chemotaxis system with flux limitation

We study a new class of Keller–Segel models, which presents a limited flux and an optimal transport of cells density according to chemical signal density. As a prototype of this class we study radially symmetric solutions to the parabolic–elliptic system ut=∇⋅(u∇uu2+|∇u|2)−χkf∇⋅(u∇v(1+|∇v|2)α),x∈Ω,t>0,0=Δv−μ+u,x∈Ω,t>0under no flux boundary conditions in a ball B=Ω⊂RN and initial condition u(x,0)=u0(x)>0,χ>0,α>0,kf>0 and μ=1|Ω|∫Ωu0dx. Under suitable conditions on α and u0 it is shown that the solution blows up in L∞-norm at a finite time Tmax and for some p>1 it blows up also in Lp-norm. The proofs are mainly based on an helpful change of variables, on comparison arguments and some suitable estimates.

Modeling and mathematical analysis of root water uptake in the rhizosphere

ABSTRACT This research focuses on elucidating a system of partial differential equations designed to model the process of water uptake by a single root within an unsaturated soil. This model extends a unidimensional root scenario by incorporating radial and axial hydraulic conductance in the root structure. The flow dynamics in the rhizosphere are represented by the Richards equation, while a diffusion equation is employed to characterize water movement within the root. The resulting system forms a strongly coupled, nonlinear parabolic-elliptic system. To establish the existence and uniqueness of a solution, we utilize the technique of semi-discretization and the Schauder-Tychonoff fixed point theorem. Additionally, we approximate the system using a mixed finite element method, and the subsequent numerical tests presented align well with the model predictions. This comprehensive approach contributes to our understanding of the intricate dynamics involved in root water uptake and provides a robust framework for further exploration in this field.

Global existence and steady states of the density-suppressed motility model with strong Allee effect

Abstract This paper considers a density-suppressed motility model with a strong Allee effect under the homogeneous Neumman boundary condition. We first establish the global existence of bounded classical solutions to a parabolic–parabolic system over an $N $-dimensional $\mathbf{(N\le 3)}$ bounded domain $\varOmega $, as well as the global existence of bounded classical solutions to a parabolic–elliptic system over the multidimensional bounded domain $\varOmega $ with smooth boundary. We then investigate the linear stability at the positive equilibria for the full parabolic case and parabolic–elliptic case, respectively, and find the influence of Allee effect on the local stability of the equilibria. By treating the Allee effect as a bifurcation parameter, we focus on the one-dimensional stationary problem and obtain the existence of non-constant positive steady states, which corresponds to small perturbations from the constant equilibrium $(1,1)$. Furthermore, we present some properties through theoretical analysis on pitchfork type and turning direction of the local bifurcations. The stability results provide a stable wave mode selection mechanism for the model considered in this paper. Finally, numerical simulations are performed to demonstrate our theoretical results.

An explicit–implicit Generalized Finite Difference scheme for a parabolic–elliptic density-suppressed motility system

In this work, a Generalized Finite Difference (GFD) scheme is presented for effectively computing the numerical solution of a parabolic–elliptic system modeling a bacterial strain with density-suppressed motility. The GFD method is a meshless method known for its simplicity for solving non-linear boundary value problems over irregular geometries. The paper first introduces the basic elements of the GFD method, and then an explicit–implicit scheme is derived. The convergence of the method is proven under a bound for the time step, and an algorithm is provided for its computational implementation. Finally, some examples are considered comparing the results obtained with a regular mesh and an irregular cloud of points.

Partial regularity for an elliptic-parabolic system modeling miscible fluid flows in porous media

Partial regularity for an elliptic-parabolic system modeling miscible fluid flows in porous media

Anisotropic parabolic-elliptic systems with degenerate thermal conductivity

In this paper, we investigate the existence and regularity of a capacity solution for a coupled nonlinear anisotropic parabolic-elliptic system, where the elliptic component of the parabolic equation involves thermal conductivities a i ( u ) that satisfy lim s → + ∞ a i ( s ) = 0 for all i = 1 , … , N . We work with anisotropic Sobolev spaces and use Schauder's fixed-point theorem to find weak solutions to approximate problems. In addition, we validate the convergence of a subsequence of approximate solutions to a capacity solution.

Global classical solvability and asymptotic behaviors of a parabolic-elliptic Chemotaxis-type system modeling crime activities

This paper is devoted to a two-dimensional parabolic-elliptic system in crime activities. The main difference between this system and the chemotaxis system with logarithmic singular sensitivity and quadratic logistic source is that the source term of this system is a mixtype quadratic term. The local existence of solutions to its intial boundary valve problem associated with homogeneous Neumann boundary conditions was considered by Rodríguez. The present study indicates that for any properly regular initial data there admits global classical solutions. Moreover, the qualitative behaviors of solutions in large time scales are considered as well.

Optimal Control of Quasi-Stationary Equations of Complex Heat Transfer with Reflection and Refraction Conditions

The paper considers a class of optimal control problems for a nonlinear parabolic-elliptic system simulating radiative heat transfer with Fresnel matching conditions on surfaces of discontinuity of the refractive index. New estimates for the solution of the initial-boundary value problem are obtained, on the basis of which the solvability of optimal control problems is proved. Non-degenerate first-order optimality conditions are derived. The results are examplified by control problems with final, boundary, and distributed observations.

Asymmetry and Condition Number of an Elliptic-Parabolic System for Biological Network Formation

Asymmetry and Condition Number of an Elliptic-Parabolic System for Biological Network Formation

Weak periodic solutions of a parabolic–elliptic system with Joule–Thomson effect

Weak periodic solutions of a parabolic–elliptic system with Joule–Thomson effect

A multi-scale simulation of retinal physiology

We present a detailed physiological model of the (human) retina that includes the biochemistry and electrophysiology of phototransduction, neuronal electrical coupling, and the spherical geometry of the eye. The model is a parabolic–elliptic system of partial differential equations based on the mathematical framework of the bi-domain equations, which we have generalized to account for multiple cell-types. We discretize in space with non-uniform finite differences and step through time with a custom adaptive time-stepper that employs a backward differentiation formula and an inexact Newton method. A refinement study confirms the accuracy and efficiency of our numerical method. Numerical simulations using the model compare favorably with experimental findings, such as desensitization to light stimuli and calcium buffering in photoreceptors. Other numerical simulations suggest an interplay between photoreceptor gap junctions and inner segment, but not outer segment, calcium concentration. Applications of this model and simulation include analysis of retinal calcium imaging experiments, the design of electroretinograms, the design of visual prosthetics, and studies of ephaptic coupling within the retina.

Hölder continuity of weak solutions to an elliptic-parabolic system modeling biological transportation network

In this paper we study the regularity of weak solutions to an elliptic-parabolic system modeling natural network formation. The system is singular and involves cubic nonlinearity. Our investigation reveals that weak solutions are Hölder continuous when the space dimension N is 2. This is achieved via an inequality associated with the Stummel-Kato class of functions and refinement of a lemma originally due to S. Campanato and C.B. Morrey ([5], p. 86).

Classical solutions to Cauchy problems for parabolic–elliptic systems of Keller-Segel type

Abstract The Cauchy problem in R n {{\mathbb{R}}}^{n} , n ≥ 2 n\ge 2 , for u t = Δ u − ∇ ⋅ ( u S ⋅ ∇ v ) , 0 = Δ v + u , ( ⋆ ) \begin{array}{r}\left\{\phantom{\rule[-1.25em]{}{0ex}}\begin{array}{l}{u}_{t}=\Delta u-\nabla \cdot \left(uS\cdot \nabla v),\\ 0=\Delta v+u,\end{array}\right.\hspace{2.0em}\hspace{2.0em}\hspace{2.0em}\left(\star )\end{array} is considered for general matrices S ∈ R n × n S\in {{\mathbb{R}}}^{n\times n} . A theory of local-in-time classical existence and extensibility is developed in a framework that differs from those considered in large parts of the literature by involving bounded classical solutions. Specifically, it is shown that for all non-negative initial data belonging to BUC ( R n ) ∩ L p ( R n ) {\rm{BUC}}\left({{\mathbb{R}}}^{n})\cap {L}^{p}\left({{\mathbb{R}}}^{n}) with some p ∈ [ 1 , n ) p\in \left[1,n) , there exist T max ∈ ( 0 , ∞ ] {T}_{\max }\in \left(0,\infty ] and a uniquely determined u ∈ C 0 ( [ 0 , T max ) ; BUC ( R n ) ) ∩ C 0 ( [ 0 , T max ) ; L p ( R n ) ) ∩ C ∞ ( R n × ( 0 , T max ) ) u\in {C}^{0}\left(\left[0,{T}_{\max });\hspace{0.33em}{\rm{BUC}}\left({{\mathbb{R}}}^{n}))\cap {C}^{0}\left(\left[0,{T}_{\max });\hspace{0.33em}{L}^{p}\left({{\mathbb{R}}}^{n}))\cap {C}^{\infty }\left({{\mathbb{R}}}^{n}\times \left(0,{T}_{\max })) such that with v ≔ Γ ⋆ u v:= \Gamma \star u , and with Γ \Gamma denoting the Newtonian kernel on R n {{\mathbb{R}}}^{n} , the pair ( u , v ) \left(u,v) forms a classical solution of ( ⋆ \star ) in R n × ( 0 , T max ) {{\mathbb{R}}}^{n}\times \left(0,{T}_{\max }) , which has the property that if T max < ∞ , then both limsup t ↗ T max ‖ u ( ⋅ , t ) ‖ L ∞ ( R n ) = ∞ and limsup t ↗ T max ‖ ∇ v ( ⋅ , t ) ‖ L ∞ ( R n ) = ∞ . \hspace{0.1em}\text{if}\hspace{0.1em}\hspace{0.33em}{T}_{\max }\lt \infty ,\hspace{1.0em}\hspace{0.1em}\text{then both}\hspace{0.1em}\hspace{0.33em}\mathop{\mathrm{limsup}}\limits_{t\nearrow {T}_{\max }}\Vert u\left(\cdot ,t){\Vert }_{{L}^{\infty }\left({{\mathbb{R}}}^{n})}=\infty \hspace{1.0em}\hspace{0.1em}\text{and}\hspace{0.1em}\hspace{1.0em}\mathop{\mathrm{limsup}}\limits_{t\nearrow {T}_{\max }}\Vert \nabla v\left(\cdot ,t){\Vert }_{{L}^{\infty }\left({{\mathbb{R}}}^{n})}=\infty . An exemplary application of this provides a result on global classical solvability in cases when ∣ S + 1 ∣ | S+{\bf{1}}| is sufficiently small, where 1 = diag ( 1 , … , 1 ) {\bf{1}}={\rm{diag}}\hspace{0.33em}\left(1,\ldots ,1) .

Existence of a capacity solution to a nonlinear parabolic–elliptic coupled system in anisotropic Orlicz-Sobolev spaces

In this work, we show the existence of a capacity solution for a nonlinear coupled parabolic–elliptic system in inhomogeneous anisotropic Orlicz-Sobolev spaces without assuming the Δ2-condition on the N-functions. This system describes the heat surge generated within a semiconductor device by an electrical direct current. This may be seen as a generalization of the so-called thermistor problem.

Inhomogeneous Problem for Quasi-Stationary Equations of Complex Heat Transfer with Reflection and Refraction Conditions

The paper considers an inhomogeneous initial-boundary value problem for a nonlinear parabolic-elliptic system simulating radiative heat transfer with Fresnel matching conditions on the surfaces of discontinuity of the refractive index. Nonlocal-in-time unique solvability of the problem is proved.

Existence and uniqueness of weak periodic solutions for a coupled parabolic-elliptic system

ased on the maximal monotone mapping theory and applying the Schauder fixed point the- orem, we prove the existence and the uniqueness of weak periodic solution for nonlinear parabolic-elliptic equations in Orlicz-Sobolev spaces, with growth nonlinearity in gradient associated with some appropriate N-functions.

Does strong repulsion lead to smooth solutions in a repulsion-attraction chemotaxis system even when starting with highly irregular initial data?

It has been well established that, in attraction-repulsion Keller–Segel systems of the form$ \begin{equation*} \left\{ \begin{aligned} u_t & = \Delta u - \chi \nabla \cdot (u\nabla v) + \xi \nabla \cdot (u\nabla w), \\ \tau v_t & = \Delta v + \alpha u - \beta v, \\ \tau w_t & = \Delta w + \gamma u - \delta w \end{aligned} \right. \end{equation*} $in a smooth bounded domain $ \Omega \subseteq \mathbb{R}^n $, $ n\in\mathbb{N} $, with Neumann boundary conditions and parameters $ \chi, \xi \geq 0 $, $ \alpha, \beta, \gamma, \delta > 0 $ and $ \tau \in \{0, 1\} $, finite-time blow-up can be ruled out in many scenarios given sufficiently smooth initial data if the repulsive chemotaxis is sufficiently stronger than its attractive counterpart. In this paper, we will go - in a sense - a step further than this by studying the same system with initial data that could already be understood as being in a blown-up state (e.g. a positive Radon measure for the first solution component) and then ask the question whether sufficiently strong repulsion has enough of a regularizing effect to lead to the existence of a smooth solution, which is still connected to said initial data in a sensible fashion. Regarding this, we in fact establish that the construction of such a solution is possible in the two-dimensional parabolic-parabolic system and the two- and three-dimensional parabolic-elliptic system under appropriate assumptions on the interaction of repulsion and attraction as well as the initial data.

Existence and supercontractive estimates for parabolic–elliptic systems

In this paper we study existence and summability of the solutions of the following parabolic–elliptic system of partial differential equations ut−div(A(x,t)∇u)=−div(uM(x)∇ψ)in Ω×(0,T), −div(M(x)∇ψ)=|u|θin Ω×(0,T), ψ(x,t)=0on ∂Ω×(0,T), u(x,t)=0on ∂Ω×(0,T), u(x,0)=u0(x)in Ω where θ∈(0,1), Ω is a bounded subset of RN, N>2, and T>0. We will prove existence results for initial data u0 in L1(Ω). Moreover, despite the datum u0 is assumed to be only a summable function and although the function uM(x)∇ψ in the divergence term of the first equation is not regular enough, there exist solutions that immediately improve their summability and belong to every Lebesgue space. Finally, we study the behavior in time of such solutions and we prove estimates that describe their blow-up for t near zero.

Existence of a Weak Solutionto the Two-Dimensional Filtration Problem in a Thin Poroelastic Layer

The paper considers a mathematical model of the joint motion of two immiscible incompressible fluids in a poroelastic medium. This model is a generalization of the classical Musket-Leverett model, in which porosity is considered to be a given function of the spatial coordinate. The model under study is based on the mass conservation equations for liquids and the porous skeleton, Darcy's law for liquids, which takes into account the movement of the porous skeleton, the Laplace formula for capillary pressure, the Maxwell-type rheological equation for porosity, and the "system as a whole" equilibrium condition. In the thin layer approximation, the original problem is reduced to the successive determination of the porosity of the solid skeleton and its velocity. Then an elliptic-parabolic system is derived for the “reduced pressure” and saturation of the wetting phase. Its solution is understood in a generalized sense due to the degeneration on the solution of the equations of the system. The proof of the existence theorem is carried out in four stages: regularization of the problem, proof of the physical maximum principle for saturation, construction of Galerkin approximations, passage to the limit in regularization parameters based on the method of compensated compactness.

Monolithic, non-iterative and iterative time discretization methods for linear coupled elliptic-parabolic systems


 We compare four numerical methods for the time discretization of linear coupled elliptic-parabolic systems.
 The monolithic method arising from an implicit Euler discretization is the primary method for solving the coupled system.
 Accelerated solution via non-iterative decoupling is possible by the semi-explicit Euler discretization, using a novel methodology from related delay differential equations. For poroelasticity, the fixed-stress splitting and undrained splitting methods enable iterative decoupled solves.
 We present formulations for the iterative methods in an abstract form and compare through numerical experiments the a priori convergence results for the four methods.