Multilevel Preconditioning of Discontinuous-Galerkin Spectral Element Methods, Part I: Geometrically Conforming Meshes

This paper is concerned with the design, analysis and implementation of preconditioning concepts for spectral Discontinuous Galerkin discretizations of elliptic boundary value problems. While presently known techniques realize a growth of the condition numbers that is logarithmic in the polynomial degrees when all degrees are equal and quadratic otherwise, our main objective is to realize full robustness with respect to arbitrarily large locally varying polynomial degrees degrees, i.e., under mild grading constraints condition numbers stay uniformly bounded with respect to the mesh size and variable degrees. The conceptual foundation of the envisaged preconditioners is the auxiliary space method. The main conceptual ingredients that will be shown in this framework to yield "optimal" preconditioners in the above sense are Legendre-Gauss-Lobatto grids in connection with certain associated anisotropic nested dyadic grids as well as specially adapted wavelet preconditioners for the resulting low order auxiliary problems. Moreover, the preconditioners have a modular form that facilitates somewhat simplified partial realizations. One of the components can, for instance, be conveniently combined with domain decomposition, at the expense though of a logarithmic growth of condition numbers. Our analysis is complemented by quantitative experimental studies of the main components.Comment: 41 pages, 11 figures; Major revision: rearrangement of the contents for better readability, part on wavelet preconditioner adde

Testing static game theory with dynamic experiments: a case study of public goods

Game theory provides predictions of behavior in many one-shot games. On the other hand, most experimenters usually play repeated games with subjects, to provide experience. To avoid subjects rationally employing strategies that are appropriate for the repeated game, experimenters typically employ a "random strangers" design in which subjects are randomly paired with others in the session. There is some chance that subjects will meet in multiple rounds, but it is claimed that this chance is so small that subjects will behave as if they are in a one-shot environment. We present evidence from public goods experiments that this claim is not always true.Game theory, experiments, public goods

Discounting in developing countries: a pilot experiment in Timor-Leste

We conduct laboratory experiments in Timor-Leste designed to test if individual discount rates vary with the time horizon for which the rate is elicited. Our experiments test a design that has been successfully employed in field experiments in developed countries, and that avoids several confounds of previous procedures. We find that there is considerable heterogeneity in individual discount rates, and that this heterogeneity is associated with observable demographic characteristics. We also find evidence that is consistent with exponential discounting behavior, although our sample sizes do not allow us to definitively reject alternative specifications. We discuss modifications of our laboratory experiments that would facilitate field experiments in Timor-Leste.

Estoque de carbono em Terra Preta do Índio no Município de Iranduba-AM.

O presente trabalho objetivou estimar o estoque de carbono até um metro de profundidade em uma área de TPI de aproximadamente seis hectares