On the smoothness of solutions of an abstract coupled thermoelasticity problem

The Cauchy problem for a system of two operator-differential equations in Hilbert space that is a generalization of a number of linear coupled thermoelasticity problems is investigated. Results concerning the high smoothness of the solutions to these equations are proved.     

Fractional-Parabolic Systems

We develop a theory of the Cauchy problem for linear evolution systems of partial differential equations with the Caputo-Dzhrbashyan fractional derivative in the time variable t. The class of systems considered in the paper is a fractional extension of the class of systems of the first order in t satisfying the uniform strong parabolicity condition. We construct and investigate the Green matrix of the Cauchy problem. While similar results for the fractional diffusion equations were based on the H-function representation of the Green matrix for equations with constant coefficients (not available in the general situation), here we use, as a basic tool, the subordination identity for a model homogeneous system. We also prove a uniqueness result based on the reduction to an operator-differential equation.     

Solvability of a boundary value problem for operator-differential equations of mixed type

We study boundary value problems for operator-differential equations of mixed type, prove existence of generalized solutions, and establish their smoothness in weighted Sobolev spaces. The results are applied to odd order forward-backward equations.     

Some properties of solutions of the cauchy problem for evolution equations

We consider the Cauchy problem for a first-order operator-differential equation with singular data. The results are used to study boundary value problems for parabolic equations with operator-valued coefficients.     

Solvability of the Cauchy problem for linear operator-differential equations with variable operator coefficients

We study the Cauchy problem for linear operator-differential equations with unbounded, nondensely defined, variable operator coefficients in a Banach space. We single out new classes of evolution equations of first and second order for which the Cauchy problem is solvable.     

On the minimax control problem for nonlinear operator-differential equations

We consider the problem of minimax control for objects describable by nonlinear operator-differential equations in Banach spaces with restrictions on the phase variables and controls. We prove solvability theorems. The method of proof is based on the theory of extremal problems for generalized operator-differential equations.Translated fromVychislitel'naya i Prikladnaya Matematika, Issue 71, 1990, pp. 114–119.     

Error estimates for the Galerkin method as applied to time-dependent equations

A projection method is studied as applied to the Cauchy problem for an operator-differential equation with a non-self-adjoint operator. The operator is assumed to be sufficiently smooth. The linear spans of eigenelements of a self-adjoint operator are used as projection subspaces. New asymptotic estimates for the convergence rate of approximate solutions and their derivatives are obtained. The method is applied to initial-boundary value problems for parabolic equations.     

Polynomial approximations of solutions of higher-order operator-differential equations

We study the Cauchy problem for higher-order operator-differential equations in a Banach space and construct polynomial approximations of its solutions.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 46, No. 7, pp. 952–955, July, 1994.     

Solvability of a class of boundary value problems for higher-order operator-differential equations

We study the existence and uniqueness of generalized solutions of a class of boundary value problems for higher-order operator-differential equations for the case in which the leading part has a multiple characteristic.     

Cauchy problems for fractional differential equations with Riemann–Liouville fractional derivatives

In this paper, we are concerned with Cauchy problems of fractional differential equations with Riemann–Liouville fractional derivatives in infinite-dimensional Banach spaces. We introduce the notion of fractional resolvent, obtain some its properties, and present a generation theorem for exponentially bounded fractional resolvents. Moreover, we prove that a homogeneous α-order Cauchy problem is well posed if and only if its coefficient operator is the generator of an α-order fractional resolvent, and we give sufficient conditions to guarantee the existence and uniqueness of weak solutions and strong solutions of an inhomogeneous α-order Cauchy problem.     

Nonlocal problem for complete second-order hyperbolic operator-differential equations with variable domains

We prove the well-posed solvability (in the strong sense) of complete second-order hyperbolic operator-differential equations with variable domains of unbounded operator coefficients under nonlocal initial conditions. We are the first to establish the well-posed solvability of the mixed problem for the complete string vibration equation with nonstationary boundary conditions and nonlocal initial conditions.     

Nonclassical statements of problems for degenerate partial differential equations

We consider problems with point initial data for first-order partial differential equations in a half-strip. The equations contain degeneration with respect to one of the variables. We prove the existence and uniqueness of smooth solutions bounded in a neighborhood of the degeneration. The structure of the considered solutions is established. Such problems arise when solving the Cauchy problem for a system of ordinary differential equations with a movable regular singular point.     

Global Helically Symmetric Solutions to 3D MHD Equations

We prove the existence and uniqueness of global strong solutions to the Cauchy problem of the three-dimensional magnetohydrodynamic equations in R3 when initial data are helically symmetric. Moreover, the large-time behavior of the strong solutions is obtained simultaneously.     

Pseudoparabolic equations with additive noise and applications

In this work we present some results on the Cauchy problem for a general class of linear pseudoparabolic equations with additive noise. We consider questions of existence and uniqueness of mild and strong solutions and well posedness for this problem. We also prove the existence and uniqueness of mild and strong solutions for a related perturbed Cauchy problem and we investigate the continuity of the solution with respect to a small parameter. The abstract results are illustrated using examples from electromagnetics and heat conduction. Copyright © 2008 John Wiley & Sons, Ltd.     

Global analysis for strong solutions to the equations of a ferrofluid flow model

In this paper we are concerned with the differential system proposed by Shliomis to describe the motion of an incompressible ferrofluid submitted to an external magnetic field. The system consists of the Navier-Stokes equations, the magnetization equations and the magnetostatic equations. No regularizing term is added to the magnetization equations. We prove the local existence of unique strong solution for the Cauchy problem and establish a finite time blow-up criterion of strong solutions. Under the smallness assumption of the initial data and the external magnetic field, we prove the global existence of strong solutions and derive a decay rate of such small solutions in L²-norm.     

The Cauchy problem for certain systems of operator-differential equations of arbitrary order in locally convex spaces

We describe an analog of the Cauchy-Kovalevskaya sufficient conditions for the analytic solvability of the Cauchy problem for systems of operator-differential equations of arbitrary order in locally convex spaces; this analog is stated in terms of the order and type of the linear operator.     

Approximation of solutions of operator-differential equations by operator polynomials

We prove theorems that characterize the classes of functions whose best approximations by algebraic polynomials tend to zero with given order. We construct approximations of solutions of operator-differential equations by polynomials in the inverse operator. Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 50, No. 11, pp. 1506–1516, November, 1998.     

On the convergence of the Galerkin method for coupled thermoelasticity problems

The Cauchy problem for a system of two operator-differential equations is considered that is an abstract statement of linear coupled thermoelasticity problems. Error estimates in the energy norm for the semidiscrete Galerkin method as applied to the Cauchy problem are established without imposing any special conditions on the projection subspaces. By way of illustration, the error estimates are applied to finite element schemes for solving the coupled problem of plate thermoelasticity considered within the framework of the Kirchhoff linearized theory. The results obtained are also applicable to the case when the projection subspaces in the Galerkin method (for the original abstract problem) are the eigenspaces of operators similar to unbounded self-adjoint positive definite operator coefficients of the original equations.     

Global existence and long-time behavior of smooth solutions of two-fluid Euler–Maxwell equations

We consider Cauchy problems and periodic problems for two-fluid compressible Euler–Maxwell equations arising in the modeling of magnetized plasmas. These equations are symmetrizable hyperbolic in the sense of Friedrichs but don?t satisfy the so-called Kawashima stability condition. For both problems, we prove the global existence and long-time behavior of smooth solutions near a given constant equilibrium state. As a byproduct, we obtain similar results for two-fluid compressible Euler–Poisson equations.     

The Cauchy Problem for Second-Order Elliptic Systems on the Plane

Regular solutions to second-order elliptic systems on the plane are representable in terms of A-analytic functions satisfying an operator equation of the Beltrami type. We prove Carleman-type formulas for reconstruction of solutions from data on a part of the boundary of the domain. We use these formulas for solving the Cauchy problems for the system of Lame equations, the Navier–Stokes system, and the system of equations of elasticity with resilience.