Optimal approximation of elliptic problems by linear and nonlinear mappings II
Journal of Complexity
Schur complements on Hilbert spaces and saddle point systems
Journal of Computational and Applied Mathematics
Compressive Algorithms--Adaptive Solutions of PDEs and Variational Problems
Proceedings of the 13th IMA International Conference on Mathematics of Surfaces XIII
Nonlinear approximation schemes associated with nonseparable wavelet bi-frames
Journal of Approximation Theory
Optimal adaptive computations in the Jaffard algebra and localized frames
Journal of Approximation Theory
SIAM Journal on Control and Optimization
Multilevel discretization of symmetric saddle point systems without the discrete LBB condition
Applied Numerical Mathematics
Journal of Scientific Computing
Multilevel Gradient Uzawa Algorithms for Symmetric Saddle Point Problems
Journal of Scientific Computing
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In this paper an adaptive wavelet scheme for saddle point problems is developed and analyzed. Under the assumption that the underlying continuous problem satisfies the inf-sup condition, it is shown in the first part under which circumstances the scheme exhibits asymptotically optimal complexity. This means that within a certain range the convergence rate which relates the achieved accuracy to the number of involved degrees of freedom is asymptotically the same as the error of the best wavelet N-term approximation of the solution with respect to the relevant norms. Moreover, the computational work needed to compute the approximate solution stays proportional to the number of degrees of freedom. It is remarkable that compatibility constraints on the trial spaces such as the Ladyzhenskaya--Babuska--Brezzi (LBB) condition do not arise. In the second part the general results are applied to the Stokes problem. Aside from the verification of those requirements on the algorithmic ingredients the theoretical analysis had been based upon, the regularity of the solutions in certain Besov scales is analyzed. These results reveal under which circumstances the work/accuracy balance of the adaptive scheme is even asymptotically better than that resulting from preassigned uniform refinements. This in turn is used to select and interpret some first numerical experiments that are to quantitatively complement the theoretical results for the Stokes problem.