In the paper some solution properties of the Love's equation are compared with those of the classical wave equation for a certain class of boundary conditions. The method of small parameter is used.

2000 Mathematics Subject Classification: 35K55, 35K60.We investigate the blow-up of the solutions to a nonlinear parabolic system with Robin boundary conditions and time dependent coefficients. We derive sufficient conditions on the nonlinearities and the initial data in order to obtain explicit lower and upper bounds for the blow up time t*.

In this paper we established the Carleman estimate for the two dimensional Lamé system with the zero Dirichlet boundary conditions. Using this estimate we proved the exact controllability result for the Lamé system with with a control locally distributed over a subdomain which satisfies to a certain type of nontrapping conditions.

We study the local exact controllability problem for the Navier-Stokes equations that describe an incompressible fluid flow in a bounded domain $\Omega$ with control distributed in a subdomain $\omega \subset \Omega \subset {ℝ}^n,n\in \{2,3\}$. The result that we obtained in this paper is as follows. Suppose that $\widehat{v}(t,x)$ is a given solution of the Navier-Stokes equations. Let $v_0\left(x\right)$ be a given initial condition and $\parallel \widehat{v}(0,·)-v_0\parallel \<\epsilon$ where $\epsilon$ is small enough. Then there exists a locally distributed control $u,\text{supp}u\subset (0,T)\times \omega$ such that the solution $v(t,x)$ of the Navier-Stokes equations:$${\partial }_{t}v-\Delta v+(v,\nabla )v=\nabla p+u+f,\text{div}v=0,v{{|}_{\partial \Omega }=0,v|}_{t=0}=v_0$$coincides with...

We study the local exact controllability problem for the Navier-Stokes equations that describe an incompressible fluid flow in a bounded domain Ω with control distributed in a subdomain $\omega \subset \Omega \subset {ℝ}^n,n\in \{2,3\}$. The result that we obtained in this paper is as follows. Suppose that $\widehat{v}(t,x)$ is a given solution of the Navier-Stokes equations. Let $v_0\left(x\right)$ be a given initial condition and $\parallel \widehat{v}(0,·)-v_0\parallel <\epsilon$ where ε is small enough. Then there exists a locally distributed control $u,\text{supp}u\subset (0,T)\times \omega$ such that the solution v(t,x) of the Navier-Stokes equations: $${\partial }_{t}v-\Delta v+(v,\nabla )v=\nabla p+u+f,\text{div}v=0,v{{|}_{\partial \Omega }=0,v|}_{t=0}=v_0$$ coincides...

Classical Gårding inequalities such as those of Hörmander, Hörmander-Melin or Fefferman-Phong are proved by pseudo-differential methods which do not allow to keep a good control on the supports of the functions under study nor on the smoothness of the coefficients of the operator. In this paper, we show by very simple calculations that in certain special situations, the results that can be obtained directly are much better than those expected thanks to the general theory.

In the talk we shall present some recent results obtained with F. Merle about compactness of blow up solutions of the critical nonlinear Schrödinger equation for initial data in $L^2\left({𝐑}^2\right)$. They are based on and are complementary to some previous work of J. Bourgain about the concentration of the solution when it approaches to the blow up time.