Dirichlet Problem for a fourth-order equation

In a rectangular domain on the plane, we consider the Dirichlet problem for a fourthorder pseudoparabolic equation with double differentiation with respect to each of the variables. To solve the problem, we reduce it to a system of Fredholm equations, whose solvability is established under additional conditions on the coefficients of the equation by the method of a priori estimates.     

非线性演化方程的切对称群分析

将优化系统的概念推广应用至切代数,并以一个二阶非线性演化方程为例,给出了方程所容许的切对称,建立了切对称的一维优化系统.并利用优化系统对所研究的方程进行了对称约化,得到了与不等价对称相对应的约化方程和不变解.     

On a double degenerate fourth-order parabolic equation

The existence of solutions to a fourth-order p-Laplacian equation with boundary degeneracy is studied. For the purpose of solving the corresponding non-degenerate (with respect to the coefficient of fourth-order term) regularized problem, a fourth-order semi-discrete elliptic problem with homogeneous boundary conditions is established and its existence and uniqueness are obtained by the functional minimization method. It follows that the approximate solutions of the non-degenerate parabolic problem are constructed and the corresponding existence and uniqueness are discovered by a limit procedure from the energy estimation method and a compactness argument. Finally, the existence and regularity of solutions for the problem with boundary degeneracy is obtained by using a regularization parameter vanishing limit.     

On the Laplace invariants of a fourth-order equation

We construct the Laplace invariants of the Bianchi equation with four independent variables and obtain determining equations expressed in terms of these invariants.     

An integrable fourth-order nonlinear evolution equation applied to thermal grooving of metal surfaces

The fourth-order nonlinear partial differential equation forsurface diffusion is approximated by a new integrable nonlinearevolution equation. Exact solutions are obtained for thermalgrooving, subject to boundary conditions representing a sectionof a grain boundary. When the slope m of the groove centre islarge, the linear model grossly overestimates the groove depth.In the linear model dimensionless groove depth increases linearlywith m, but in the nonlinear model it approaches an upper limitA nontrivial similarity solution is found for the limiting caseof a thermal groove whose central slope is vertical.     

Global behavior for a fourth-order rational difference equation

In this paper, we use a method different from the known literature to investigate the global behavior of the following fourth-order rational difference equation:

     

Reduction method for a fourth-order equation on a graph

We justify a method that permits one to reduce a boundary value problem on a graph to a problem on a narrower subset provided that the right-hand side of the differential equation is identically zero on some subgraph of the original graph. We find the signs of the coefficients in the boundary conditions of the reduced problem and clarify the relationship between these coefficients.     

Non-homogeneous boundary conditions for a fourth-order diffusion equation

The existence of classical solutions to a one-dimensional non-linear fourth-order elliptic equation arising in quantum semiconductor modeling is proved for a class of non-homogeneous boundary conditions using degree theory. Furthermore, some non-existence results for other classes of boundary conditions are presented. To cite this article: P. Amster et al., C. R. Acad. Sci. Paris, Ser. I 346 (2008).     

Periodic boundary-value problem for a fourth-order differential equation

In the present paper we obtain sufficient conditions for solvability of a periodic boundary-value problem for a fourth-order ordinary differential equation. The research technique is based on a solvability theorem for a quasi-linear operator equation in the resonance case. We formulate sufficient conditions for existence of periodic solutions in terms of the initial equation. The main result of the paper clarifies the existence theorem established by B. Mehry and D. Shadman in Sci. Iran. 15 (2), 182–185 (2008).     

On some two-point problems for a fourth-order equation

We obtain sufficient conditions for the existence of a solution of two boundary value problems for a nonlinear fourth-order equation of general form.     

Qualitative properties for a fourth-order rational difference equation

In this paper, we use a method different from the known literature to investigate the qualitative properties of the following fourth-order rational difference equation:

     

Long-time behavior for a nonlinear fourth-order parabolic equation

We study the asymptotic behavior of solutions of the initial- boundary value problem, with periodic boundary conditions, for a fourth-order nonlinear degenerate diffusion equation with a logarithmic nonlinearity. For strictly positive and suitably small initial data we show that a positive solution exponentially approaches its mean as time tends to infinity. These results are derived by analyzing the equation verified by the logarithm of the solution.

     

Equivalence and equation solvability problems for the alternating group A4

It is observed in this paper that the complexities of the equivalence and the equation solvability problems are not determined by the clone of the algebra. In particular, we prove that for the alternating group on four elements these problems have complexity in P; if we extend the group by the commutator as an extra operation, then the equivalence problem is coNP-complete and the equation solvability problem is NP-complete.     

Multiplicity of solutions for a fourth-order quasilinear nonhomogeneous equation

We consider a fourth-order quasilinear nonhomogeneous equation which is equivalent to a nonhomogeneous Hamiltonian system. The purpose of this work is to prove the existence of at least two solutions for such equation when a certain parameter is small enough. Furthermore, under an additional hypothesis on positiveness of the nonhomogeneous part we prove that our solutions are positive.     

Homoclinic orbits to a saddle-center in a fourth-order differential equation

We study homoclinic orbits to a saddle-center of a fourth-order ordinary differential equation, which is invariant under the transformation x→−x, involving an eigenvalue parameter q and an odd, piece-wise, cubic-type nonlinearity. It is found that for a sequence of eigenvalues which tends to infinity, homoclinic orbits exist whose complexity increases as the eigenvalue becomes larger. These orbits are found to be embedded in branches of homoclinic orbits to periodic orbits as x→±∞.