On the solvability of a functional equation

This article studies properties of solutions of a functional equation arising in dynamic programming of multistage decision processes. A sufficient condition for the existence, uniqueness and iterative approximation of solutions of the functional equation is established. A few other behaviours of solutions for certain functional equations which are particular cases of the functional equation are discussed. The results presented in this article extend, improve and unify some known results in literature.     

On unique solvability of the absolute value equation

It is proved that the singular value condition σ _max(|B|) < σ _min(A) implies unique solvability of the absolute value equation Ax + B|x| = b for each right-hand side b. This is a generalization of an earlier result by Mangasarian and Meyer proved for the special case of B = −I. Supported by the Czech Republic Grant Agency under grants 201/09/1957 and 201/08/J020, and by the Institutional Research Plan AV0Z10300504.     

Solving the hammerstein integral equation in the irregular case by successive approximations

The branches of a solution of the nonlinear integral equation

On the solvability for the mixed-type Lyapunov equation

^** Email: xsf{at}math.pku.edu.cn^*** Email: mscheng{at}math.pku.edu.cn In this paper, the linear matrix equation X = AXB^* + BXA^* +Q is considered, which is called the mixed-type Lyapunov equation.Some necessary and sufficient conditions for the existence ofa unique solution are presented. Since a Hermitian positivesemidefinite solution is important from the application pointof view, some sufficient conditions for the existence of a Hermitianpositive semidefinite solution are derived.     

Kawahara-BO方程Cauchy问题的局部可解性

研究Kawahara-BO方程在低正则Sobolev空间Hr上的局部适定性和极限行为.证明了:当r>-7/5时,对任意的初始值uo ∈Hr,Kawahara-BO方程的Cauchy问题存在唯一的解u∈C([0,T],Hr)∩Xr,s;当BO项系数λ趋向于O时,Kawahara-BO方程的解收敛到Kawahara方程的解.     

On the solvability of the Riccati matrix algebraic equation

We obtain conditions of solvability of the Riccati matrix algebraic equation.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 11, pp. 1591–1593, November, 1994.     

Approximate analytical solution of Blasius'' equation

The Blasius' equation f″′ + ff″/2=0, with boundary conditions f(0) = f′(0)0, f′(+∞)=1 is studied in this paper. An approximate analytical solution is obtained via the variational iteration method. The comparison with Howarth's numerical solution reveals that the proposed method is of high accuracy.     

Approximate solution of the Fokker-Planck-Kolmogorov equation

For the Fokker-Planck-Kolmogorov equation, the higher approximations are constructed by using the Bogolyubov averaging method.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 47, No. 3, pp. 351–361, March, 1995.     

On solvability of Dirichlet problem for second order elliptic equation

The paper gives some solvability conditions of the Dirichlet problem for the second order elliptic equation $$ - div(A(x)\nabla u) + (\bar b(x),\nabla u) - div(\bar c(x)u) + d(x)u = f(x) - divF(x),x \in Q,u|_{\partial Q} = u_0 \in L_2 (\partial Q) $$ in bounded domain Q ? R _n (n ≥ 2) with smooth boundary ?Q ∈ C ₁. In particular, it is proved that if the homogeneous problem has only the trivial solution, then for any u ₀ ∈L ₂(?Q) and f, F from the corresponding functional spaces the solution of the non-homogeneous problem exists, from Gushchin’s space $ C_{n - 1} (\bar Q) $ and the following inequality is true: $$ \begin{gathered} \left\| u \right\|_{C_{n - 1} (\bar Q)}^2 + \mathop \smallint \limits_Q r\left| {\nabla u} \right|^2 dx \leqslant \hfill \\ \leqslant C\left( {\left\| {u_0 } \right\|_{L_2 (\partial Q)}^2 + \mathop \smallint \limits_Q r^3 (1 + |\ln r|)^{3/2} f^2 dx + \mathop \smallint \limits_Q r(1 + |\ln r|)^{3/2} |F|^2 dx} \right) \hfill \\ \end{gathered} $$ where r(x) is the distance from a point x ∈ Q to the boundary ?Q and the constant C does not depend on u ₀, f and F.     

On the solvability of a complete two-dimensional hypersingular integral equation

We study the solvability of a complete two-dimensional linear hypersingular integral equation that contains a hypersingular integral operator in which the integral is understood in the sense of Hadamard finite value as well as an integral operator in which the integral is understood in the sense of principal value, an integral operator with a weakly singular kernel, and an integral-free term. We consider smooth solutions in the class of functions that have Hölder continuous derivatives outside a neighborhood of the boundary. We prove the Fredholm alternative and estimate the norm of the solution in a special metric.     

Local solvability in top degree of the semilinear Kohn equation

We study the local solvability problem for a class of semilinear equations whose linear part is the Kohn Laplacian, acting on top degree forms. We also study the validity of the Poincaré lemma, in top degree, for semilinear perturbations of the tangential Cauchy–Riemann complex.     

Approximate solution of one singular integro-differential equation

In this paper we construct and theoretically justify a computational scheme for solving the Cauchy problem for a singular integro-differential equation of the first-order, where the integral over a segment of the real axis is understood in the sense of the Cauchy principal value. In addition, we study and solve approximately the integral equation with a special logarithmic kernel. We obtain uniform estimates for errors of approximate formulas. Orders of errors of approximate solutions are proved to be proportional to the order of the approximation error for the derivative of the density of the singular integral in the integro-differential equation.     

Approximate controllability of a non-autonomous differential equation

In this paper, we establish the approximate controllability results for a non-autonomous functional differential equation using the theory of linear evolution system, Schauder fixed point theorem, and by making use of resolvent operators. The results obtained in this paper, improve the existing ones in this direction, to a considerable extent. An example is also given to illustrate the abstract results.     

扰动Boussinesq方程的近似守恒律

构造了具有扰动项的Boussinesq方程的近似守恒向量和近似守恒律.在方程允许拉格朗日函数的情况下,利用欧拉方程的部分拉格朗日函数方法,研究了含有一阶线性组合扰动项的Boussineq方程的近似守恒律.给出了该方程的近似守恒向量及近似守恒律的分类结果.     

Approximate symmetry of a nonlinear heat equation

Using the idea of asymptotic methods of Krylov-Bogolyubov-Mitropol'skii, we study the approximate Galilean symmetry of a multidimensional nonlinear heat equation.Translated from Ukrainsklii Matematicheskii Zhurnal, Vol 43, No. 6, pp. 833–837, September 1991.     

Approximate controllability of a parabolic integrodifferential equation

In this paper, we obtain the approximate controllability of a parabolic integrodifferential equation with interior controls. The proof relies on the linear operator semigroup theory and the controllability theory for abstract equations. Copyright © 2013 John Wiley & Sons, Ltd.     

Approximate solutions of a nonlinear differential equation

Approximate solutions of a nonlinear differential equation ẍ + α^mx² = β^mx^{m + 2} (m⩾1) are approximate solution is exact for a particular initial value.