On étudie la position des pôles de diffusion du problème de Dirichlet pour l’équation des ondes amorties du type ${\partial }_t^2-\Delta +a\left(x\right){\partial }_t$ dans un domaine extérieur. Sous la condition du « contrôle géométrique extérieur », on déduit alors le comportement des solutions en grand temps. On calcule en particulier le meilleur taux de décroissance de l’énergie locale en dimension impaire d’espace.

For the Dirichlet Laplacian in the exterior of a strictly convex obstacle, we show that the number of scattering poles of modulus $\le r$ in a small angle $\theta$ near the real axis, can be estimated by Const ${\theta }^{3/2}{r}^n$ for $r$ sufficiently large depending on $\theta$. Here $n$ is the dimension.

We consider the norm closure 𝔄 of the algebra of all operators of order and class zero in Boutet de Monvel's calculus on a compact manifold X with boundary ∂X. Assuming that all connected components of X have nonempty boundary, we show that K₁(𝔄) ≃ K₁(C(X)) ⊕ ker χ, where χ: K₀(C₀(T*Ẋ)) → ℤ is the topological index, T*Ẋ denoting the cotangent bundle of the interior. Also K₀(𝔄) is topologically determined. In case ∂X has torsion free K-theory, we get K₀(𝔄) ≃ K₀(C(X)) ⊕ K₁(C₀(T*Ẋ)).

Given a hypoelliptic boundary value problem on $\omega \times [0,T)$ with $\omega$ an open set in ${\mathbf{R}}^n$, $(n\>1)$, we show by matrix triangulation how to reduce it to two uncoupled first order systems, and how to estimate the eigenvalues of the corresponding matrices. Parametrices for the first order systems are constructed. We then characterize hypoellipticity up to the boundary in terms of the Calderon operator corresponding to the boundary value problem.

This work is devoted to a systematic study of the microlocal regularity properties of pseudo-differential operators with the transmission property. We introduce a “boundary singular spectrum”, denoted $\partial W{F}_{\omega }\left(u\right)$ for distributions $u\in D^{\text{'}}({\mathbf{R}}_{+}^n)$, regular in the normal variable $x_n$ (thus, $\partial W{F}_{\omega }\left(u\right)=\varnothing$ means that $u\in {\cap }_{s+t=1/2}{H}^{s+t}$ near the boundary), and it is shown that $\partial W{F}_{\omega -m}\left[P\right(u^0{)}_{x_n\>0}]$ is a subset of $\partial WF\left(u\right)$ if $P$ has degree $m$ and the transmission property. We finally prove that these results can bef used to examinate the (microlocal) regularity of the solutions of differential...

2000 Mathematics Subject Classification: 26A33 (primary), 35S15In this paper, a space fractional diffusion equation (SFDE) with nonhomogeneous boundary conditions on a bounded domain is considered. A new matrix transfer technique (MTT) for solving the SFDE is proposed. The method is based on a matrix representation of the fractional-in-space operator and the novelty of this approach is that a standard discretisation of the operator leads to a system of linear ODEs with the matrix raised to the...

2000 Mathematics Subject Classification: 26A33 (primary), 35S15 (secondary)This paper provides a new method and corresponding numerical schemes to approximate a fractional-in-space diffusion equation on a bounded domain under boundary conditions of the Dirichlet, Neumann or Robin type. The method is based on a matrix representation of the fractional-in-space operator and the novelty of this approach is that a standard discretisation of the operator leads to a system of linear ODEs with the matrix...

We consider an elliptic pseudodifferential equation in a multi-dimensional cone, and using the wave factorization concept for an elliptic symbol we describe a general solution of such equation in Sobolev-Slobodetskii spaces. This general solution depends on some arbitrary functions, their quantity being determined by an index of the wave factorization. For identifying these arbitrary functions one needs some additional conditions, for example, boundary conditions. Simple boundary value problems,...