Tricomi problem for a functional-differential advanced-retarded Lavrent’ev–Bitsadze equation

We study a boundary value problem for the Lavrent’ev–Bitsadze equation with functional delay and advance. The general solution is constructed. The problem is uniquely solvable.     

Correctness of the Dirichlet problem for the Lavrent’ev–Bitsadze equation

It is shown that the Dirichlet problem in a multidimensional domain for the Lavrent’ev–Bitsadze equation is uniquely solvable. A criterion of the uniqueness of the solution is obtained.     

Nonlocal Dezin’s problem for Lavrent’ev–Bitsadze equation

Using the method of spectral analysis, for the mixed type equation u_xx + (sgny)u_yy = 0 in a rectangular domain we establish a criterion of uniqueness of its solution satisfying periodicity conditions by the variable x, a nonlocal condition, and a boundary condition. The solution is constructed as the sum of a series in eigenfunctions for the corresponding one-dimensional spectral problem. At the investigation of convergence of the series, the problem of small denominators occurs. Under certain restrictions on the parameters of the problem and the functions, included in the boundary conditions, we prove uniform convergence of the constructed series and stability of the solution under perturbations of these functions.     

The boundary-value problem for Lavrent’Ev–Bitsadze equation with two internal lines of change of a type

We study the problem with boundary conditions of the first and second kind on the boundary of a rectangular domain for an equation with two internal perpendicular lines of change of a type. With the use of the spectral method we prove the unique solvability of the mentioned problem. The eigenvalue problem for an ordinary differential equation obtained by separation of variables is not self-adjoint, and the system of root functions is not orthogonal. We construct the corresponding biorthogonal system of functions and prove its completeness. This allows us to establish a criterion for the uniqueness of the solution to the problem under consideration. We construct the solution as the sum of the biorthogonal series.     

Eigenvalues and eigenfunctions of the Gellerstedt problem for the multidimensional Lavrent’ev–Bitsadze equation

We determine eigenvalues and eigenfunctions of the Gellerstedt problem for the multidimensional Lavrent’ev–Bitsadze equation.     

The inverse problem for the Lavrent’ev–Bitsadze equation connected with the search of elements in the right-hand side

We consider an equation of mixed elliptic-hyperbolic type, whose right-hand side represents a product of two one-dimensional functions. We establish a criterion for the unique solvability of this equation and construct its solution as a sum of series on the set of its eigenfunctions. Under certain constraints imposed on the ratio of the rectangle sides, on boundary functions, and on known multipliers in the right-hand side of the equation, we obtain estimates separating small denominators that appear in coefficients of constructed series from zero.     

A. A. Dezin’s problem for inhomogeneous Lavrent’ev–Bitsadze equation

We establish a uniqueness criterion for solution of nonlocal Dezin’s problem for an equation of mixed elliptic-hyperbolic type. The solution is constructed as a sum of a series in eigenfunctions of the corresponding one-dimensional spectral problem. In the proof of its convergence there arises a problem on small denominators arises. Under certain restrictions on the given parameters and functions we prove the convergence of constructed series in the class of regular solutions.     

Discretized Lavrent’ev regularization for the autoconvolution equation

Lavrent’ev regularization for the autoconvolution equation was considered by Janno J. in Lavrent’ev regularization of ill-posed problems containing nonlinear near-to-monotone operators with application to autoconvolution equation, Inverse Prob. 2000;16:333–348. Here this study is extended by considering discretization of the Lavrent’ev scheme by splines. It is shown how to maintain the known convergence rate by an appropriate choice of spline spaces and a proper choice of the discretization level. For piece-wise constant splines the discretized equation allows for an explicit solver, in contrast to using higher order splines. This is used to design a fast implementation by means of post-smoothing, which provides results, which are indistinguishable from results obtained by direct discretization using cubic splines.     

Uniqueness of the Solution of the Gellerstedt Problem for the Lavrent’ev–Bitsadze Equation with a Spectral Parameter

Differential Equations - Some theorems on the uniqueness of the solution of the Gellerstedt problem for the Lavrent’ev–Bitsadze equation with a spectral parameter $$\lambda $$ with data...     

Dirichlet Problem for Lavrent’ev–Bitsadze Equation With Loaded Summands

We study the first boundary-value problem for loaded equation of elliptic-hyperbolic type in rectangular domain. We establish a criterion of uniqueness. A solution to the problem is constructed in the formof the sum of a series. In substantiation of existence of a solution to a problem small denominators appear. We obtain the estimates about a separation from zero of denominators with the corresponding asymptotics. They allow to prove existence of a solution in a class of regular solutions.     

Some Uniqueness Theorems for the Solution of the Gellerstedt Problem for the Lavrent’ev–Bitsadze Equation with a Spectral Parameter

Differential Equations - Some theorems on the uniqueness of the solution of the Gellerstedt problem for the Lavrent’ev–Bitsadze equation with a spectral parameter $$lambda $$ are...     

A criterion for the unique solvability of the dirichlet spectral problem in a cylindrical domain for a multidimensional Lavrent’ev-Bitsadze equation

We obtain a criterion for the unique solvability of the spectral problem in a cylindrical domain for a multidimensional Lavrent’ev-Bitsadze equation.     

Solution of the Bitsadze–Samarskii problem for a parabolic system in a semibounded domain

We consider a nonlocal initial–boundary value Bitsadze–Samarskii problem for a spatially one-dimensional parabolic second-order system in a semibounded domain with nonsmooth lateral boundary. The boundary integral equation method is used to construct a classical solution of this problem under the condition that the vector function on the right-hand side in the nonlocal boundary condition only has a continuous derivative of order 1/2 vanishing at t = 0. The smoothness of the solution is studied.     

The boundary-value problem for the Lavrent’ev-Bitsadze equation with unknown right-hand side

We study the inverse problem for the Lavrent’ev-Bitsadze equation in a rectangular domain. We construct its solution as a series of eigenfunctions for the corresponding problem on eigenvalues and establish a criterion for its uniqueness. We also prove the stability of the obtained solution.     

A Criterion for the Uniqueness of the Solution of the Tricomi Problem for the Multidimensional Lavrent’ev–Bitsadze Equation

Differential Equations - An example of a mixed domain in which the solution of the Tricomi problem is trivial is given. A criterion for the uniqueness of the classical solution of this problem is...     

On the solution of the Gellerstedt problem for the Lavrent’ev-Bitsadze equation

We study the solvability of the Gellerstedt problem for the Lavrent??ev-Bitsadze equation under an inhomogeneous boundary condition on the half-circle of the ellipticity domain of the equation, homogeneous boundary conditions on external, internal, and parallel side characteristics of the hyperbolicity domain of the equation, and the transmission conditions on the type change line of the equation.     

On the convergence of the Lavrent’ev method for an integral equation of the first kind with involution

The convergence in the mean-square metric of the Lavrent’ev regularizationmethod for an integral equation with involution is established. The proof of the convergence is based on studying the behavior of the resolvent of a certain integro-differential equation related to the original equation.     

On the solvability of the tricomi problem for the Lavrent’ev-Bitsadze equation with mixed boundary conditions

We study the existence of a regular (classical) solution of the Tricomi problem for the Lavrent’ev-Bitsadze equation with mixed boundary conditions. We find conditions under which the homogeneous problem has only the zero solution and give an example in which the homogeneous Tricomi problem has a nonzero solution. We also study the solvability of the inhomogeneous Tricomi problem.     

Inverse problem for an equation of mixed type with the Lavrent’ev-Bitsadze operator and with a nonlocal boundary condition

For an equation of the mixed elliptic-hyperbolic type, we study the inverse problem with a nonlocal condition relating the derivatives of the solution on the elliptic and hyperbolic parts of the boundary. We prove a uniqueness criterion and construct the solution in the form of a Fourier series.