Sign-definiteness of solution to inhomogeneous higher-order equation of mixed parabolic-hyperbolic type

We study solutions of a polycaloric equation and an equation of mixed parabolichyperbolic type of the second order. We prove the sign-definiteness of the solution in dependence of the right-hand side of the equation. Based on these results we study the sign-definiteness of a solution to a higher-order inhomogeneous equation of mixed parabolic-hyperbolic type in dependence on the right-hand side of the equation.     

Initial boundary and inverse problems for the inhomogeneous equation of a mixed parabolic-hyperbolic equation

A problem with inhomogeneous boundary and initial conditions is studied for an inhomogeneous equation of mixed parabolic-hyperbolic type in a rectangular domain. The solution is constructed as the sum of an orthogonal series. A criterion for the uniqueness of the solution is established. It is shown that the uniqueness of the solution and the convergence of the series depend on the ratio of the sides of the rectangle from the hyperbolic part of the mixed domain. On the basis of this problem, inverse problems for finding the factors of the time-dependent right-hand sides of the original equation of mixed type are stated and studied for the first time. The corresponding uniqueness theorems and the existence of solutions are proved using the theory of integral equations for inverse problems.     

Justification of the Fourier method for an inhomogeneous hyperbolic equation with random right-hand side

We consider an inhomogeneous hyperbolic equation with homogeneous initial and boundary conditions and a random right-hand side. In the case where the right-hand side of the equation is a centered sample-continuous Gaussian field, we establish conditions for the existence of a solution of the first boundary-value problem of mathematical physics in the form of a series uniformly convergent in probability.Translated from Ukrainskyi Matematychnyi Zhurnal, Vol. 56, No. 5, pp. 616–624, May, 2004.     

Steady-state oscillations in the continuously inhomogeneous medium described by the Ovsyannikov equation

Using the group analysis methods, for the Ovsyannikov equation with maximal symmetry which describes steady-state oscillations in a continuous inhomogeneous medium, we obtain exact solutions to boundary-value problems for some regions (generalized Poisson formulas), which in particular can serve as test solutions for simulating steady-state oscillations in continuous inhomogeneous media. We find operators acting on the set of solutions in a one-parameter family of these equations.     

A study of the solvability of the generalized equation of filtration of an inhomogeneous fluid

We study the existence of solutions of the generalized equation of filtration of an inhomogeneous fluid and prove that they are unique. We study the smoothness properties of the solutions when the right-hand sides of the equation belong to various spaces.This work is carried out using the machinery of rigged Hilbert spaces and energy inequalities.Translated fromVychislitel'naya i Prikladnaya Matematika, Issue 71, 1990, pp. 77–84.     

Solution of a mixed problem with oblique derivatives in the boundary conditions for the inhomogeneous string vibration equation without continuing the data

We find closed-form recursion formulas for the unique classical solution of a mixed problem describing forced vibrations of a bounded string under two boundary modes with timedependent oblique derivatives. The formulas do not use any continuation of the problem data. We obtain conditions on the right-hand side of the equation necessary and sufficient for the well-posed global solvability of the problem.     

Summability of formal solutions to the n-dimensional inhomogeneous heat equation

The Cauchy problem for n-dimensional inhomogeneous complex heat equation is considered. The Borel summability of formal solutions is characterised in terms of analytic continuation with an appropriate growth condition of some function connected with the inhomogeneity and the Cauchy data.     

Explicit solutions of the inhomogeneous dirac equation

In this paper we establish a general principle which may be used to construct many explicit solutions to special inhomogeneous Dirac equations with distributional right-hand side. These solutions are presented as series of products of Clifford algebra valued functions which themselves satisfy Dirac equations in a lower dimension. We also present several special examples, including plane waves, zonal functions, Cauchy kernels and electromagnetic fields.     

Total integrals of Ablowitz-Segur solutions for the inhomogeneous Painlevé II equation

In this paper, we establish a formula determining the value of the Cauchy principal value integrals of the real and purely imaginary Ablowitz-Segur solutions for the inhomogeneous second Painlevé equation. Our approach relies on the analysis of the corresponding Riemann-Hilbert problem and the construction of an appropriate parametrix in a neighborhood of the origin. Obtained integral formulas are consistent with already known analogous results for the Ablowitz-Segur solutions of the homogeneous Painlevé II equation.     

Factorized equation of vibrations of a finite string with nonstationary second directional derivatives at the endpoints

We obtain closed-form recursion formulas for the classical solutions of a mixed problem for the general inhomogeneous factorized equation of vibrations of a bounded string with second directional derivatives in the boundary conditions, in which the coefficients multi-plying the first of the two directional derivatives are independent of time. We study the case of boundary conditions in which all first directional derivatives are not directed along the characteristics of the equation. We obtain necessary and sufficient conditions on the right-hand side and the initial and boundary data of the problem for its well-posed global solvability in the set of classical solutions.     

Mixed problems for the string vibration equation with nonlocal conditions of the general form at the right endpoint and with an inhomogeneous condition at the left endpoint

We consider four mixed problems for the string vibration equation with zero initial conditions, with a Bitsadze–Samarskii boundary condition of the general form at the right endpoint, and with an inhomogeneous Neumann or Dirichlet condition at the left endpoint. We prove the uniqueness of a generalized solution (in the sense of Il’in) of these problems and obtain an analytic representation of these solutions. The solution of each of the problems is represented in the form of a linear combination of functions constructed from the problem data, and recursion formulas for the coefficients of this linear combination are obtained.     

Inhomogeneous infinity Laplace equation

We present the theory of the viscosity solutions of the inhomogeneous infinity Laplace equation in domains in Rn. We show existence and uniqueness of a viscosity solution of the Dirichlet problem under the intrinsic condition f does not change its sign. We also discover a characteristic property, which we call the comparison with standard functions property, of the viscosity sub- and super-solutions of the equation with constant right-hand side. Applying these results and properties, we prove the stability of the inhomogeneous infinity Laplace equation with nonvanishing right-hand side, which states the uniform convergence of the viscosity solutions of the perturbed equations to that of the original inhomogeneous equation when both the right-hand side and boundary data are perturbed. In the end, we prove the stability of the well-known homogeneous infinity Laplace equation , which states the viscosity solutions of the perturbed equations converge uniformly to the unique viscosity solution of the homogeneous equation when its right-hand side and boundary data are perturbed simultaneously.     

Positivity of solutions to inhomogeneous mixed-type equations of higher orders

We study the solution to inhomogeneous mixed-type elliptic-hyperbolic equations of higher orders. We prove that the solution sign is constant and depends on the sign of the right-hand side of the equation.     

Solutions of fixed sign of higher-order inhomogeneous equations of mixed elliptic-hyperbolic type

For a higher-order inhomogeneous equation of mixed elliptic-hyperbolic type, the property of the solution to be of fixed sign is established, depending on the sign of the right-hand side.     

On an inhomogeneous problem for parabolic-hyperbolic equation

We study a boundary value problem for an inhomogeneous parabolic-hyperbolic equation with a noncharacteristic type change line. Boundary conditions of the first kind are posed on characteristics in the parabolic and hyperbolic parts of the domain where the equation is given, and a condition of the third kind is posed on the noncharacteristic part of the boundary in the parabolic part. First, we study the solvability of an inhomogeneous initial–boundary value problem for a parabolic equation.     

Construction of polynomial solutions to the Dirichlet problem for the polyharmonic equation in a ball

An algorithm is proposed for the analytical construction of a polynomial solution to Dirichlet problem for an inhomogeneous polyharmonic equation with a polynomial right-hand side and polynomial boundary data in the unit ball.     

Polynomial solutions of the Dirichlet problem for the biharmonic equation in the ball

We find a polynomial solution of the Dirichlet problem for the inhomogeneous biharmonic equation with polynomial right-hand side and polynomial boundary data in the unit ball. To this end, we use the closed-form representation of harmonic functions in the Almansi formula.     

Improved inhomogeneous Strichartz estimates for the Schrödinger equation

We study inhomogeneous Strichartz estimates for the Schrödinger equation for dimension n?3. Using a frequency localization, we obtain some improved range of Strichartz estimates for the solution of inhomogeneous Schrödinger equation except dimension n=3.     

Asymptotic expansion of the solution of a differential-difference equation of general form

We obtain an asymptotic expansion of the solution of an mth-order inhomogeneous differential-difference equation of general form. We establish an integral estimate with a submultiplicative weight for the remainder of the expansion depending on the existence of the corresponding submultiplicative moment of the right-hand side of the equation.     

Alternative solution of the inhomogeneous linear differential equation of order two

In this paper, we present an alternative method for solving the general inhomogeneous linear ordinary differential equation (ODE) of order two. The solution appears in the standard form as the sum of the solution of the equivalent homogeneous problem and the particular solution of the inhomogeneous problem at hand. The main advantage of the method exposed herein is that the particular solution is computable from two different integrals. This allows the problem solver to choose the simplest integral with which to work with in order to get the final solution. For illustrative purposes we employ the method presented to aid in the solution of some example problems including the inhomogeneous Klein-Gordon equation.