scholarly journals Convergence estimates for abstract second order differential equations with two small parameters and Lipschitzian nonlinearities

2021 ◽  
Vol 38 (1) ◽  
pp. 179-200
Author(s):  
ANDREI PERJAN ◽  
◽  
GALINA RUSU ◽  
Keyword(s):  
A Priori Estimates ◽  
Real Hilbert Space ◽  
A Priori ◽  
Singular Behavior ◽  
Estimates Of Solutions ◽  
Second Order Differential Equations ◽  
Priori Estimates ◽  
Unperturbed Problem ◽  
Small Parameters ◽  
Convergence Estimates

In a real Hilbert space $H$ we consider the following singularly perturbed Cauchy problem ... We study the behavior of solutions $u_{\varepsilon\delta}$ in two different cases: $\varepsilon\to 0$ and $\delta \geq \delta_0>0;$ $\varepsilon\to 0$ and $\delta \to 0,$ relative to solution to the corresponding unperturbed problem.We obtain some {\it a priori} estimates of solutions to the perturbed problem, which are uniform with respect to parameters, and a relationship between solutions to both problems. We establish that the solution to the unperturbed problem has a singular behavior, relative to the parameters, in the neighbourhood of $t=0.$

Abstract linear second order differential equations with two small parameters and depending on time operators

2017 ◽  
Vol 33 (2) ◽  
pp. 233-246
Author(s):  
ANDREI PERJAN ◽  
◽  
GALINA RUSU ◽  
Keyword(s):  
Boundary Layer ◽  
A Priori Estimates ◽  
Real Hilbert Space ◽  
A Priori ◽  
Estimates Of Solutions ◽  
Layer Function ◽  
Priori Estimates ◽  
Unperturbed Problem ◽  
Small Parameters ◽  
Boundary Layer Function

In a real Hilbert space H consider the following singularly perturbed Cauchy problem. We study the behavior of solutions uεδ to this problem in two different cases: ε → 0 and δ ≥ δ0 > 0; ε → 0 and δ → 0, relative to solution to the corresponding unperturbed problem. We obtain some a priori estimates of solutions to the perturbed problem, which are uniform with respect to parameters, and a relationship between solutions to both problems. We establish that the solution to the perturbed problem has a singular behavior, relative to the parameters, in the neighbourhood of t = 0. We show the boundary layer and boundary layer function in both cases.

scholarly journals Two parameter singular perturbation problems for sine-Gordon type equations

2021 ◽  
Vol 38 (1) ◽  
pp. 201-215
Author(s):  
ANDREI PERJAN ◽  
◽  
GALINA RUSU ◽  
Keyword(s):  
A Priori Estimates ◽  
A Priori ◽  
Type Equation ◽  
Estimates Of Solutions ◽  
Priori Estimates ◽  
Small Parameters ◽  
Convergence Estimates ◽  
The Difference ◽  
Perturbation Problems ◽  
Two Parameter

In the real Sobolev space $H_0^1(\Omega)$ we consider the Cauchy-Dirichlet problem for sine-Gordon type equation with strongly elliptic operators and two small parameters. Using some {\it a priori} estimates of solutions to the perturbed problem and a relationship between solutions in the linear case, we establish convergence estimates for the difference of solutions to the perturbed and corresponding unperturbed problems. We obtain that the solution to the perturbed problem has a singular behavior, relative to the parameters, in the neighbourhood of $t=0.$

Existence of bistable waves for a nonlocal and nonmonotone reaction-diffusion equation

2019 ◽  
Vol 150 (2) ◽  
pp. 721-739
Author(s):  
Sergei Trofimchuk ◽  
Vitaly Volpert
Keyword(s):  
Diffusion Equation ◽  
A Priori Estimates ◽  
Travelling Waves ◽  
A Priori ◽  
Unbounded Domains ◽  
Reaction Diffusion ◽  
Reaction Diffusion Equation ◽  
Nonlocal Nonlinearity ◽  
Estimates Of Solutions ◽  
Priori Estimates

AbstractReaction-diffusion equation with a bistable nonlocal nonlinearity is considered in the case where the reaction term is not quasi-monotone. For this equation, the existence of travelling waves is proved by the Leray-Schauder method based on the topological degree for elliptic operators in unbounded domains and a priori estimates of solutions in properly chosen weighted spaces.

A priori estimates of solutions of nonlinear boundary value problems for singular in a phase variable second order differential inequalities

2014 ◽  
Vol 21 (2) ◽  
Author(s):  
Ivan Kiguradze
Keyword(s):  
A Priori Estimates ◽  
A Priori ◽  
Nonlocal Boundary ◽  
Nonlocal Boundary Conditions ◽  
Second Order ◽  
Phase Variable ◽  
Differential Inequalities ◽  
Nonlinear Boundary Value Problems ◽  
Estimates Of Solutions ◽  
Priori Estimates

Abstract.For singular in a phase variable second order differential inequalities, a priori estimates of positive solutions, satisfying nonlinear nonlocal boundary conditions, are established.

scholarly journals Estimates of Solutions of Elliptic Differential-Difference Equations with Degeneration

2018 ◽  
Vol 64 (1) ◽  
pp. 131-147
Author(s):  
V A Popov
Keyword(s):  
Difference Equations ◽  
A Priori Estimates ◽  
Difference Operator ◽  
A Priori ◽  
Difference Operators ◽  
Elliptic Differential Operator ◽  
Friedrichs Extension ◽  
Estimates Of Solutions ◽  
Priori Estimates ◽  
Differential Difference Equation

We consider a second-order differential-difference equation in a bounded domain Q ⊂ Rn. We assume that the differential-difference operator contains some difference operators with degeneration corresponding to differentiation operators. Moreover, the differential-difference operator under consideration cannot be expressed as a composition of a difference operator and a strongly elliptic differential operator. Degenerated difference operators do not allow us to obtain the G˚arding inequality. We prove a priori estimates from which it follows that the differential-difference operator under consideration is sectorial and its Friedrichs extension exists. These estimates can be applied to study the spectrum of the Friedrichs extension as well. It is well known that elliptic differential-difference equations may have solutions that do not belong even to the Sobolev space W 1(Q). However, using the obtained estimates, we can prove some smoothness of solutions, though not in the whole domain Q, but inside some subdomains Qr generated by the shifts of the boundary, where U Qr = Q.

scholarly journals Periodic solutions for second order differential equations with indefinite singularities

2019 ◽  
Vol 9 (1) ◽  
pp. 994-1007 ◽  
Author(s):  
Shiping Lu ◽  
Xingchen Yu
Keyword(s):  
Differential Equations ◽  
Periodic Solutions ◽  
A Priori Estimates ◽  
A Priori ◽  
Second Order ◽  
Continuation Theorem ◽  
Second Order Differential Equations ◽  
Priori Estimates ◽  
Negative Constant

Abstract In this paper, the problem of periodic solutions is studied for second order differential equations with indefinite singularities $$\begin{array}{} \displaystyle x''(t)+ f(x(t))x'(t)+\varphi(t)x^m(t)-\frac{\alpha(t)}{x^\mu(t)}+\frac{\beta(t)}{x^y (t)}=0, \end{array}$$ where f ∈ C((0, +∞), ℝ) may have a singularity at the origin, the signs of φ and α are allowed to change, m is a non-negative constant, μ and y are positive constants. The approach is based on a continuation theorem of Manásevich and Mawhin with techniques of a priori estimates.

scholarly journals Existence of solutions of a non-variational bi-harmonic system via fixed point theory

Filomat ◽  
2018 ◽  
Vol 32 (12) ◽  
pp. 4113-4130 ◽  
Author(s):  
Idir Mechai ◽  
Metib Alghamdi ◽  
Habib Yazidi
Keyword(s):  
Numerical Solutions ◽  
Existence Of Solutions ◽  
A Priori Estimates ◽  
Fixed Point Theory ◽  
A Priori ◽  
Point Theory ◽  
Estimates Of Solutions ◽  
Priori Estimates ◽  
Theoretical Results ◽  
Harmonic System

We prove existence of a positive solution for a system of non-variational bi-harmonic equations. Furthermore, we give some a priori estimates of solutions and a non-existence result. In addition we compute numerical solutions to illustrate the theoretical results.

A priori estimates of solutions of boundary value problems for two-dimensional systems of singular differential inequalities

2011 ◽  
Vol 18 (1) ◽  
pp. 163-175
Author(s):  
Nino Partsvania
Keyword(s):  
Boundary Value Problems ◽  
A Priori Estimates ◽  
Boundary Value ◽  
A Priori ◽  
Differential Inequalities ◽  
Two Dimensional ◽  
Point Boundary ◽  
Estimates Of Solutions ◽  
Priori Estimates ◽  
Singular Coefficients

Abstract A priori estimates of solutions of two-point boundary value problems for two-dimensional systems of differential inequalities with singular coefficients are established.

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