Contributions to the Theory of Optimal Tests

This paper considers tests which maximize the weighted average power (WAP). The focus is on determining WAP tests subject to an uncountable number of equalities and/or inequalities. The unifying theory allows us to obtain tests with correct size, similar tests, and unbiased tests, among others. A WAP test may be randomized and its characterization is not always possible. We show how to approximate the power of the optimal test by sequences of nonrandomized tests. Two alternative approximations are considered. The rst approach considers a sequence of similar tests for an increasing number of boundary conditions. This discretization allows us to implement the WAP tests in practice. The second method nds a sequence of tests which approximate the WAP test uniformly. This approximation allows us to show that WAP similar tests are admissible. The theoretical framework is readily applicable to several econometric models, including the important class of the curved-exponential family. In this paper, we consider the instrumental variable model with heteroskedastic and autocorrelated errors (HAC-IV) and the nearly integrated regressor model. In both models, we nd WAP similar and (locally) unbiased tests which dominate other available tests.

The role of the BNDES in the Brazilian development financing: contributions from the paper “towards a legal theory of finance” of Katharina Pistor

This paper aims to verify the main contributions and adjustments that the paper “Towards a Legal Theory of Finance” from Katharina Pistor may bring to the role of the Brazilian National Bank for Economic and Social Development (BNDES) in the Brazilian development financing. In order to do so, I work with two questions in this paper: (i) such theory presents elements which allow analyzing the role of the BNDES and from there, if it is required, adjustments can be made in the governance of the BNDES? and (ii) there are academics and scholars that, together with the theory, also contribute with the improvement of the BNDES role in the development of Brazil?

A theory of weekly specials

Multiproduct retailers facing similar costs and serving the same public commonly announce different weekly specials. These promotional prices also seem to evolve randomly over the weeks. Here, weekly specials are viewed as the strategic outcome of an oligopolistic price competition among multiproduct retail stores facing nonconvex costs. Existence of an equilibrium in mixed strategies is proven. ldentical stores serving the same public will never charge the same price vector with probability one (cross-store price dispersion). Mixed strategies can generate random price dispersion over time in the repeated version of the mode!.

Toward a theory of international currency : a step further

We generalize the two-country, two-currency model of Matsuyama, Kiyotaki and Matsui to resolve two "shortcomings" in their approach. First, we endogenize prices and excb.ange rates. Second, we introduce monetary policy. We then use the model to address the following new questions: How does the fact that a currency circulates intemationally affect its purcb.asing power? Where does an intemational currency purcb.ase more? What are the effects on seignorage and welfare when a currency becomes intemational? How is policy affected by concems of currency substitution? How are national monetary policies connected, and what is the scope for international cooperation?

A Theory of voter experimentation in repeated elections

Nesse artigo, eu desenvolvo e analiso um modelo de dois perí odos em que dois polí ticos competem pela preferência de um eleitor representativo, que sabe quão benevolente é um dos polí ticos mas é imperfeitamente informado sobre quão benevolente é o segundo polí tico. O polí tico conhecido é interpretado como um incumbente de longo prazo, ao passo que o polí tico desconhecido é interpretado como um desa fiante menos conhecido. É estabelecido que o mecanismo de provisão de incentivos inerente às elei cões - que surge através da possibilidade de não reeleger um incumbente - e considerações acerca de aquisi cão de informa cão por parte do eleitor se combinam de modo a determinar que em qualquer equilí brio desse jogo o eleitor escolhe o polí tico desconhecido no per íodo inicial do modelo - uma a cão à qual me refi ro como experimenta cão -, fornecendo assim uma racionaliza cão para a não reelei cão de incumbentes longevos. Especifi camente, eu mostro que a decisão do eleitor quanto a quem eleger no per odo inicial se reduz à compara cão entre os benefí cios informacionais de escolher o polí tico desconhecido e as perdas econômicas de fazê-lo. Os primeiros, que capturam as considera cões relacionadas à aquisi cão de informa cão, são mostrados serem sempre positivos, ao passo que as últimas, que capturam o incentivo à boa performance, são sempre não-negativas, implicando que é sempre ótimo para o eleitor escolher o polí tico desconhecido no per íodo inicial.

The spenders-hoarders theory of capital accumulations, wealth distribution and fiscal policy

This paper proposes a simple OLG model which is consistent with the essential facts about consumer behavior, capital accumulation and wealth distribution, and yields some new and surprising conclusions about fiscal policy. By considering a society in which individuais are distinguished according to two characteristics, altruism and wealth preference, we show that those who in the long run hold the bulk of private capital are not so rnuch motivated by dynastic altruism as by preference for wealth. Two types of social segmentation can result with different wcalth distribution. To a large extcnt our results seem to fit reality better than those obtained with standard optimal growth models in which dynastic altruism ( or r ate o f impatience) is the only source of heterogeneity: overaccumulation can appear, public debt and unfunded pensions are not neutra!, estate taxation can improve the welfare of the top wealthy.

Effects of dredging operations on sediment quality: contaminant mobilization in dredged sediments from the Port of Santos, SP, Brazil

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Theory of small aspect ratio waves in deep water

In the limit of small values of the aspect ratio parameter (or wave steepness) which measures the amplitude of a surface wave in units of its wave-length, a model equation is derived from the Euler system in infinite depth (deep water) without potential flow assumption. The resulting equation is shown to sustain periodic waves which on the one side tend to the proper linear limit at small amplitudes, on the other side possess a threshold amplitude where wave crest peaking is achieved. An explicit expression of the crest angle at wave breaking is found in terms of the wave velocity. By numerical simulations, stable soliton-like solutions (experiencing elastic interactions) propagate in a given velocities range on the edge of which they tend to the peakon solution. (c) 2005 Elsevier B.V. All rights reserved.

On the algebraic K theory of the massive D8 and M9-branes

In this paper we review some basic relations of algebraic K theory and we formulate them in the language of D-branes. Then we study the relation between the D8-branes wrapped on an orientable, compact manifold W in a massive Type IIA, supergravity background and the M9-branes wrapped on a compact manifold Z in a massive d = 11 supergravity background from the K-theoretic point of view. By interpreting the D8-brane charges as elements of K-0(C(W)) and the (inequivalent classes of) spaces of gauge fields on the M9-branes as the elements of K-0(C(Z) x ((k) over bar*) G) where G is a one-dimensional compact group, a connection between charges and gauge fields is argued to exists. This connection could be realized as a composition map between the corresponding algebraic K theory groups.

Higher-derivative theory of (2+1)-dimensional gravity

Higher-derivative gravity in 2 + 1 dimensions is considered. The general solution of the linearized field equations in a three-dimensional version of the Teyssandier gauge is obtained, and from that the solution for a static pointlike source is found. The deflection of light rays is also analysed. (C) 2001 Elsevier B.V. B.V. All rights reserved.

Conformal field theory of AdS background with Ramond-Ramond flux

We review a formalism of superstring quantization with manifest six-dimensional spacetime supersymmetry, and apply it to AdS(3) x S-3 backgrounds with Ramond-Ramond flux. The resulting description is a conformal field theory based on a sigma model whose target space is a certain supergroup SU' (2\2).

Theory of optical dispersive shock waves in photorefractive media

The theory of optical dispersive shocks generated in the propagation of light beams through photorefractive media is developed. A full one-dimensional analytical theory based on the Whitham modulation approach is given for the simplest case of a sharp steplike initial discontinuity in a beam with one-dimensional striplike geometry. This approach is confirmed by numerical simulations, which are extended also to beams with cylindrical symmetry. The theory explains recent experiments where such dispersive shock waves have been observed.

Non-Hermitian multichannel theory of ultracold collisions modified by intense light fields tuned to the red of the trapping transition

We develop a systematic scheme to treat binary collisions between ultracold atoms in the presence of a strong laser field, tuned to the red of the trapping transition. We assume that the Rabi frequency is much less than the spacing between adjacent bound-state resonances, In this approach we neglect fine and hyperfine structures, but consider fully the three-dimensional aspects of the scattering process, up to the partial d wave. We apply the scheme to calculate the S matrix elements up to the second order in the ratio between the Rabi frequency and the laser detuning, We also obtain, fur this simplified multichannel model, the asymmetric line shapes of photoassociation spectroscopy, and the modification of the scattering length due to the light field at low, but finite, entrance kinetic energy. We emphasize that the present calculations can be generalized to treat more realistic models, and suggest how to carry out a thorough numerical comparison to this semianalytic theory. [S1050-2947(98)04902-6].