This study is mainly dedicated to the development and analysis ofnon-overlapping domain decomposition methods for solving continuous-pressurefinite element formulations of the Stokes problem. These methods have thefollowing special features. By keeping the equations and unknowns unchanged atthe cross points, that is, points shared by more than two subdomains, one caninterpret them as iterative solvers of the actual discrete problem directlyissued from the finite element scheme. In this way, the good stabilityproperties of continuous-pressure mixed finite element approximations of theStokes system are preserved. Estimates ensuring that each iteration can beperformed in a stable way as well as a proof of the convergence of theiterative process provide a theoretical background for the application of therelated solving procedure. Finally some numerical experiments are given todemonstrate the effectiveness of the approach, and particularly to compare itsefficiency with an adaptation to this framework of a standard FETI-DP method.

In this paper we introduce and analyze some non-overlapping multiplicative Schwarz methods for discontinuous Galerkin (DG) approximations of elliptic problems. The construction of the Schwarz preconditioners is presented in a unified framework for a wide class of DG methods.For symmetric DG approximations we provide optimal convergence bounds for the corresponding error propagation operator, and we show that the resulting methods can be accelerated by using suitable Krylov space solvers. A discussion on the issue of preconditioning non-symmetric DG approximations of elliptic problems is also included. Extensive numerical experiments to confirm the theoretical results and to assess the robustness and the efficiency of the proposed preconditioners are provided.

In this paper, the convergence of a Neumann-Dirichlet algorithm to approximateCoulomb's contact problem between two elastic bodies is proved in a continuous setting. In this algorithm, the natural interface between the two bodies is retained as a decomposition zone.


We propose and study some new additive, two-level non-overlapping Schwarz preconditioners for the solution of the algebraic linear systems arising from a wide class of discontinuous Galerkin approximations of elliptic problems that have been proposed up to now. In particular, two-level methods for both symmetric and non-symmetric schemes are introduced and some interesting features, which have no analog in the conforming case, are discussed.Both the construction and analysis of the proposed domain decomposition methods are presented in a unified framework. For symmetric schemes, it is shown that the condition number of the preconditioned system is of order O(H/h), where H and h are the mesh sizes of the coarse and fine grids respectively, which are assumed to be nested. For non-symmetric schemes, we show by numerical computations that the Eisenstat et al. [SIAM J. Numer. Anal.20 (1983) 345–357] GMRES convergence theory, generally used in the analysis of Schwarz methods for non-symmetric problems, cannot be applied even if the numerical results show that the GMRES applied to the preconditioned systems converges in a finite number of steps and the proposed preconditioners seem to be scalable.Extensive numerical experiments to validate our theory and to illustrate the performance and robustness of the proposed two-level methods are presented.


Three non-overlapping domain decomposition methods are proposed for thenumericalapproximation of time-harmonic Maxwell equations with damping (i.e., in a conductor). Foreach method convergence is proved and, for the discrete problem, the rate ofconvergenceof the iterative algorithm is shown to be independent of the number ofdegrees of freedom.

In a recent paper [4] we have proposed and analyseda suitable mathematical modelwhich describes the coupling of the Navier-Stokes with theOseen equations.In this paper we propose a numerical solution of the coupledproblem by subdomain splitting.After a preliminary analysis, we prove a convergence result foran iterative algorithm that alternates the solution of the Navier-Stokes problem to the one of the Oseen problem.