Smoothed Particle Interpolation

Smoothed particle hydrodynamics (SPH) discretization techniques are generalized to develop a method, smoothed particle interpolation (SPI), for solving initial value problems of systems of non-hydrodynamical nature. Under this approach, SPH is viewed as strictly an interpolation scheme and, as such, suitable for solving general hyperbolic and parabolic equations. The SPI method is tested on (1) the wave equation with inhomogeneous sound speed and (2) Burgers equation. The efficiency of SPI is studied by comparing SPI solutions to those obtained with standard finite difference methods. It is shown that the power of SPI arises when the smoothing particles are free to move.Comment: 13 pages (LaTeX), 9 figures (not included), [email protected]

The Imprint of Proper Motion of Nonlinear Structures on the Cosmic Microwave Background

We investigate the imprint of nonlinear matter condensations on the Cosmic Microwave Background (CMB) in an $\Omega=1$, Cold Dark Matter (CDM) model universe. Temperature anisotropies are obtained by numerically evolving matter inhomogeneities and CMB photons from the beginning of decoupling until the present epoch. The underlying density field produced by the inhomogeneities is followed from the linear, through the weakly clustered, into the fully nonlinear regime. We concentrate on CMB temperature distortions arising from variations in the gravitational potentials of nonlinear structures. We find two sources of temperature fluctuations produced by time-varying potentials: (1) anisotropies due to intrinsic changes in the gravitational potentials of the inhomogeneities and (2) anisotropies generated by the peculiar, bulk motion of the structures across the microwave sky. Both effects generate CMB anisotropies in the range of 10^{-7} \siml \Delta T/T \siml 10^{-6} on scales of $\sim 1^{\circ}$. For isolated structures, anisotropies due to proper motion exhibit a dipole-like signature in the CMB sky that in principle could yield information on the transverse velocity of the structures.Comment: 9 pages, 7 figures (included), uuencoded postcript fil

Unexpected Media Coverage and Stock Market Outcomes : Evidence from Chemical Disasters.

Using the event-study methodology and multivariate regressions, this paper examines the intensity of media coverage, its determinants and its marginal effect on stock returns following chemical disasters. To do this, we build an original dataset of chemical explosions that occurred worldwide from 1990-2005. First, our results show that news coverage increases with the social and environmental consequences of the accident. Second, to deal with the fact that news coverage is determined simultaneously with stock returns, we suggest two valid and original instrumental variables: a measure of the firm’s newsworthiness and a measure of daily news pressure at the time of the disaster. We find that unexpected news coverage due to chemical disasters also respond to these conjunctural factors, and is truly exogenous to abnormal returns. Third, we show that, all else being equal (pollution, number of casualties, and firm profile), the stock market reaction to intense press coverage is delayed, and becomes negative in the long-term. At the same time, there is clear evidence that in the first days news coverage mitigates the market value losses. We interpret these results as evidence that investors are slow to recognize the extent of the loss associated with the public implications of news coverage (e.g., image and public trust deterioration). In addition, in contrast toprevious studies, we argue that press coverage is not necessarily associated with increased investor attention.Corporate Social Responsibility; Pollution; Media; Efficient Market Hypothesis; Behavioral Finance;

Individual homogenization in large-scale systems: on the politics of computer and social architectures

One determining characteristic of contemporary sociopolitical systems is their power over increasingly large and diverse populations. This raises questions about power relations between heterogeneous individuals and increasingly dominant and homogenizing system objectives. This article crosses epistemic boundaries by integrating computer engineering and a historicalphilosophical approach making the general organization of individuals within large-scale systems and corresponding individual homogenization intelligible. From a versatile archeological-genealogical perspective, an analysis of computer and social architectures is conducted that reinterprets Foucault’s disciplines and political anatomy to establish the notion of politics for a purely technical system. This permits an understanding of system organization as modern technology with application to technical and social systems alike. Connecting to Heidegger’s notions of the enframing (Gestell) and a more primal truth (anfänglicheren Wahrheit), the recognition of politics in differently developing systems then challenges the immutability of contemporary organization. Following this critique of modernity and within the conceptualization of system organization, Derrida’s democracy to come (à venir) is then reformulated more abstractly as organizations to come. Through the integration of the discussed concepts, the framework of Large-Scale Systems Composed of Homogeneous Individuals (LSSCHI) is proposed, problematizing the relationships between individuals, structure, activity, and power within large-scale systems. The LSSCHI framework highlights the conflict of homogenizing system-level objectives and individual heterogeneity, and outlines power relations and mechanisms of control shared across different social and technical systems