Nous exposons un exemple de non unicité du problème de Cauchy non caractéristique pour l’équation de transport associé à un champ de vecteurs borné, à divergence nulle et néanmoins à coefficients peu réguliers

We study the asymptotic behavior of $\lambda v_{\lambda }$ as $\lambda \to 0^{+}$, where $v_{\lambda }$ is the viscosity solution of the following Hamilton-Jacobi-Isaacs equation (infinite horizon case)$$\lambda v_{\lambda }+H(x,D{v}_{\lambda })=0,$$with$$H(x,p):=\underset{b\in B}{min}\underset{a\in A}{max}\{-f(x,a,b)·p-l(x,a,b)\}.$$We discuss the cases in which the state of the system is required to stay in an $n$-dimensional torus, called periodic boundary conditions, or in the closure of a bounded connected domain $\Omega \subset {ℝ}^n$ with sufficiently smooth boundary. As far as the latter is concerned, we treat both the case of the Neumann boundary conditions (reflection on the boundary)...

We study the asymptotic behavior of $\lambda v_{\lambda }$ as $\lambda \to 0^{+}$, where $v_{\lambda }$ is the viscosity solution of the following Hamilton-Jacobi-Isaacs equation (infinite horizon case) $$\lambda v_{\lambda }+H(x,D{v}_{\lambda })=0,$$ with $$H(x,p):=\underset{b\in B}{min}\underset{a\in A}{max}\{-f(x,a,b)·p-l(x,a,b)\}.$$ We discuss the cases in which the state of the system is required to stay in an n-dimensional torus, called periodic boundary conditions, or in the closure of a bounded connected domain $\Omega \subset {}^n$ with sufficiently smooth boundary. As far as the latter is concerned, we treat both the case of the Neumann boundary conditions (reflection on the...

We study the microlocal analyticity of solutions $u$ of the nonlinear equation$$u_t=f(x,t,u,u_x)$$where $f(x,t,{\zeta }_0,\zeta )$ is complex-valued, real analytic in all its arguments and holomorphic in $({\zeta }_0,\zeta )$. We show that if the function $u$ is a $C^2$ solution, $\sigma \in \text{Char}{L}^u$ and $\frac{1}{i}\sigma \left([L^u,\overline{L^u}]\right)\<0$ or if $u$ is a $C^3$ solution, $\sigma \in \text{Char}{L}^u$, $\sigma \left([L^u,\overline{L^u}]\right)=0$, and $\sigma \left([L^u,[L^u,\overline{L^u}]]\right)\ne 0$, then $\sigma \notin W{F}_{a}u$. Here $W{F}_{a}u$ denotes the analytic wave-front set of $u$ and Char$L^u$ is the characteristic set of the linearized operator. When $m=1$, we prove a more general result involving the repeated brackets of $L^u$ and $\overline{L^u}$ of any order.

The Povzner equation is a version of the nonlinear Boltzmann equation, in which the collision operator is mollified in the space variable. The existence of stationary solutions in $L^1$ is established for a class of stationary boundary-value problems in bounded domains with smooth boundaries, without convexity assumptions. The results are obtained for a general type of collision kernels with angular cutoff. Boundary conditions of the diffuse reflection type, as well as the given incoming profile, are...