Structural models and structural change: analytical principles and methodological issues

Structural analysis is the main topic of this paper and structural change is a dominant theme of the present work. The analysis of structural models and of theories of structural changes carried out in this paper has a double meaning. On the one hand, it allows to pick up several essential principles that characterize these models, on the other hand, it should allow us to reconsider some important methodological issues under a new light, such as different methods of decomposition of the productive systems, the problem of complexity and the strategies to reduce complexity. Moreover, the paper tries to compare Quesnay’s Tableau, taken as a benchmark model, with Leontief’s, von Neumann’s and Sraffa’s models to pick up the different features of these models with respect to his theoretical framework and also to identify their characteristics for structural analysis and structural change.

Numerical loop quantum cosmology: an overview

A brief review of various numerical techniques used in loop quantum cosmology and results is presented. These include the way extensive numerical simulations shed insights on the resolution of classical singularities, resulting in the key prediction of the bounce at the Planck scale in different models, and the numerical methods used to analyze the properties of the quantum difference operator and the von Neumann stability issues. Using the quantization of a massless scalar field in an isotropic spacetime as a template, an attempt is made to highlight the complementarity of different methods to gain understanding of the new physics emerging from the quantum theory. Open directions which need to be explored with more refined numerical methods are discussed.Comment: 33 Pages, 4 figures. Invited contribution to appear in Classical and Quantum Gravity special issue on Non-Astrophysical Numerical Relativit

The spatial correlations in the velocities arising from a random distribution of point vortices

This paper is devoted to a statistical analysis of the velocity fluctuations arising from a random distribution of point vortices in two-dimensional turbulence. Exact results are derived for the correlations in the velocities occurring at two points separated by an arbitrary distance. We find that the spatial correlation function decays extremely slowly with the distance. We discuss the analogy with the statistics of the gravitational field in stellar systems.Comment: 37 pages in RevTeX format (no figure); submitted to Physics of Fluid

hp-version time domain boundary elements for the wave equation on quasi-uniform meshes

Solutions to the wave equation in the exterior of a polyhedral domain or a screen in $\mathbb{R}^3$ exhibit singular behavior from the edges and corners. We present quasi-optimal $hp$-explicit estimates for the approximation of the Dirichlet and Neumann traces of these solutions for uniform time steps and (globally) quasi-uniform meshes on the boundary. The results are applied to an $hp$-version of the time domain boundary element method. Numerical examples confirm the theoretical results for the Dirichlet problem both for screens and polyhedral domains.Comment: 41 pages, 11 figure

Climbing the Density Functional Ladder: Non-Empirical Meta-Generalized Gradient Approximation Designed for Molecules and Solids

The electron density, its gradient, and the Kohn-Sham orbital kinetic energy density are the local ingredients of a meta-generalized gradient approximation (meta-GGA). We construct a meta-GGA density functional for the exchange-correlation energy that satisfies exact constraints without empirical parameters. The exchange and correlation terms respect {\it two} paradigms: one- or two-electron densities and slowly-varying densities, and so describe both molecules and solids with high accuracy, as shown by extensive numerical tests. This functional completes the third rung of ``Jacob's ladder'' of approximations, above the local spin density and GGA rungs.Comment: 4 pages, 1 figure, 1 table. updated with minor and yet necessary corrections. New references are adde

The Contributions of Two Eminent Japanese Scholars on the Development of Economic Theories: Michio Morishima and Takashi Negishi

There can be no doubt that Michio Morishima and Takashi Negishi are two of the most important historians of economic thought of the recent past. Both authors contributed numerous papers and books to the subject, dealing with the works of major economists from the very inception of systematic economic thought at the time of the classical economists up until modern times. And both authors combined a vivid interest in modern economic theory with an interest in what past masters had to say. The paper assesses and compares the motivations of the two authors to engage in the history of economic theories, their similar, but different approaches to do historical research, and their achievements in this regard. Given the remarkable amount of work each one of them accomplished, the paper has to focus attention on a subset of the themes the two authors dealt with. The emphasis will be on (i) their treatment of the classical theories of value, distribution and capital accumulation, especially those of Adam Smith and David Ricardo, (ii) their discussion of the contributions of Karl Marx and some Marxists, (iii) their interpretation of some early and mature marginalist economists, especially Léon Walras, Eugen von Böhm-Bawerk and Knut Wicksell, and (iv) their views about the achievements of John Maynard Keynes. Given the intrinsic complexity of each of these themes, it goes without saying that the paper is bound to proceed largely in terms of synthetic statements.Negishi, Takashi; Morishima, Michio; general equilibrium; Marxist economics; trade; growth