The Calderón problem for quasilinear elliptic equations

In this paper we show uniqueness of the conductivity for the quasilinear Calderón's inverse problem. The nonlinear conductivity depends, in a nonlinear fashion, of the potential itself and its gradient. Under some structural assumptions on the direct problem, a real-valued conductivity allowing a small analytic continuation to the complex plane induce a unique Dirichlet-to-Neumann (DN) map. The method of proof considers some complex-valued, linear test functions based on a point of the boundary of the domain, and a linearization of the DN map placed at these particular set of solutions.     

The lifespan for quasi-linear wave equations with multiple-speeds in space dimensions n ≥ 3

In this paper, we consider the Cauchy problem for quasi-linear wave equations with multiple propagation speeds in space dimensions n ≥ 3. The case when the nonlinearities depending on both the unknown functions and their derivatives are studied. Based on some Klainerman-Sideris type weighted estimates and space-time L ² estimates, the lifespan for quasilinear multi-speeds wave equations of small amplitude solutions are presented.     

On the Dirichlet–Riquier problem for biharmonic equations

In the paper, it is proved that the distribution of a measurable polynomial on an infinite-dimensional space with log-concave measure is absolutely continuous if the polynomial is not equal to a constant almost everywhere. A similar assertion is proved for analytic functions and for some other classes of functions. Properties of distributions of norms of polynomial mappings are also studied. For the space of measurable polynomial mappings of a chosen degree, it is proved that the L ¹-norm with respect to a log-concave measure is equivalent to the L ¹-norm with respect to the restriction of the measure to an arbitrarily chosen set of positive measure.     

Cauchy–Dirichlet problem for second-order hyperbolic equations in cylinders with non-smooth base

This paper is concerned with the smoothness of generalized solutions of the Cauchy–Dirichlet problem for the second-order hyperbolic equation in domains with a conical point.     

On the Dirichlet problem for Monge-Ampère type equations

In this paper, we prove second derivative estimates together with classical solvability for the Dirichlet problem of certain Monge-Ampére type equations under sharp hypotheses. In particular we assume that the matrix function in the augmented Hessian is regular in the sense used by Trudinger and Wang in Ann. Scoula Norm. Sup. Pisa Cl. Sci. VIII, 143–174 2009 in their study of global regularity in optimal transportation as well as the existence of a smooth subsolution. The latter hypothesis replaces a barrier condition also used in their work. The applications to optimal transportation and prescribed Jacobian equations are also indicated.     

The stability problem and special solutions for the 5-components Maxwell–Bloch equations

For the 5-components Maxwell–Bloch system the stability problem for the isolated equilibria is completely solved. Using the geometry of the symplectic leaves, a detailed construction of the homoclinic orbits is given. Studying the problem of invariant sets for the system, we discover a rich family of periodic solutions in explicit form.     

On the exterior Dirichlet problem for the Monge–Ampère equation in dimension two

In this paper, we consider the Dirichlet problem for the Monge–Ampère equation on exterior domains in dimension two and prove a theorem on the existence of solutions with prescribed asymptotic behavior at infinity.     

The venttse’ problem for nonlinear elliptic equations

The solvability of the fully nonlinear stationary Venttsel' problem is established. The equation and the boundary condition are assumed to be uniformly elliptic. Bibliography: 12 titles. Translated fromProblemy Matematicheskogo Analiza, No. 19, 1999, pp. 3–26.     

Existence and nonexistence to exterior Dirichlet problem for Monge–Ampère equation

We consider the exterior Dirichlet problem for Monge–Ampère equation with prescribed asymptotic behavior. Based on earlier work by Caffarelli and the first named author, we complete the characterization of the existence and nonexistence of solutions in terms of their asymptotic behaviors.     

Solving the Dirichlet problem for Navier–Stokes equations by probabilistic approach

We construct a number of layer methods for Navier-Stokes equations (NSEs) with no-slip boundary conditions. The methods are obtained using probabilistic representations of solutions to NSEs and exploiting ideas of the weak sense numerical integration of stochastic differential equations. Despite their probabilistic nature, the proposed methods are nevertheless deterministic.     

On the coupled NBEM and FEM for a class of nonlinear exterior Dirichlet problem in R~(2*)

In this paper, based on the natural boundary reduction advanced by Feng and Yu, we couple the finite element approach with the natural boundary element method to study the weak solvability and Galerkin approximation of a class of nonlinear exterior boundary value problems. The analysis is mainly based on the variational formulation with constraints. We prove the error estimate of the finite element solution and obtain     

The Cauchy problem for semi-linear Klein–Gordon equations in de Sitter spacetime

The Cauchy problem for semi-linear Klein–Gordon equations is considered in de Sitter spacetime. The nonlinear terms are power type or exponential type. The local and global solutions are shown in the energy class.     

The Calderón problem for Hilbert couples

We prove that intermediate Banach spaces\(\mathcal{A}\) and\(\mathcal{B}\) with respect to arbitrary Hilbert couples\(\bar {H}\) and\(\bar {K}\) are exact interpolation if and onlyif they are exactK-monotonic, i.e. the condition\(f^0 \in \mathcal{A}\) and the inequality\(K(t,g^0 ;\bar {K}) \leqslant K(t,f^0 ;\bar {H}),t > 0\), implyg⁰∈B and ‖g⁰‖B≤‖f⁰‖ _A (K is Peetre’sK-functional). It is well known that this property is implied by the following: for each ?>1 there exists an operator\(T:\bar {H} \to \bar {K}\) such thatTf⁰=g⁰, and\(K(t,Tf;\bar {K}) \leqslant \rho K(t,f;\bar {H}),f \in \mathcal{H}_0 + \mathcal{H}_1 ,t > 0\). Verifying the latter property, it suffices to consider the “diagonal case” where\(\bar {H} = \bar {K}\) is finite-dimensional, in which case we construct the relevant operators by a method which allows us to explicitly calculate them. In the strongest form of the theorem it is shown that the statement remains valid when substituting ?=1. The result leads to a short proof of Donoghue’s theorem on interpolation functions, as well as Löwner’s theorem on monotone matrix functions.     

The Cauchy problem for non-autonomous nonlinear Schrödinger equations

In this paper we study the Cauchy problem for cubic nonlinear Schrödinger equation with space- and time-dependent coefficients on ∝^m and \(\mathbb{T}^m \). By an approximation argument we prove that for suitable initial values, the Cauchy problem admits unique local solutions. Global existence is discussed in the cases of m = 1, 2.     

The Cauchy problem for the 2D magnetohydrodynamic-α equations

In this paper, we consider the Cauchy problem for the 2D incompressible magnetohydrodynamics-$\alpha$ (MHD-$\alpha$) equations. We obtain the global solution for the 2D incompressible MHD-$\alpha$ simulation model in the fractional index Sobolev space, and prove that the incompressible MHD-$\alpha$ equations reduce to the incompressible homogeneous MHD equations as $\alpha \to 0$, and the solution of MHD-$\alpha$ equations will converge to the weak solution of the corresponding MHD equations. Moreover, it is convenient to construct a numerical algorithm based on an iteration scheme in our proof.