Atmospheric Calorimetry above 1019^{19} eV: Shooting Lasers at the Pierre Auger Cosmic-Ray Observatory

The Pierre Auger Cosmic-Ray Observatory uses the earth's atmosphere as a calorimeter to measure extensive air-showers created by particles of astrophysical origin. Some of these particles carry joules of energy. At these extreme energies, test beams are not available in the conventional sense. Yet understanding the energy response of the observatory is important. For example, the propagation distance of the highest energy cosmic-rays through the cosmic microwave background radiation (CMBR) is predicted to be strong function of energy. This paper will discuss recently reported results from the observatory and the use of calibrated pulsed UV laser "test-beams" that simulate the optical signatures of ultra-high energy cosmic rays. The status of the much larger 200,000 km$^3$ companion detector planned for the northern hemisphere will also be outlined.Comment: 6 pages, 11 figures XIII International Conference on Calorimetry in High Energy Physic

Variance asymptotics and scaling limits for Gaussian Polytopes

Let $K_n$ be the convex hull of i.i.d. random variables distributed according to the standard normal distribution on $\R^d$. We establish variance asymptotics as $n \to \infty$ for the re-scaled intrinsic volumes and $k$-face functionals of $K_n$, $k \in \{0,1,...,d-1\}$, resolving an open problem. Variance asymptotics are given in terms of functionals of germ-grain models having parabolic grains with apices at a Poisson point process on $\R^{d-1} \times \R$ with intensity $e^h dh dv$. The scaling limit of the boundary of $K_n$ as $n \to \infty$ converges to a festoon of parabolic surfaces, coinciding with that featuring in the geometric construction of the zero viscosity solution to Burgers' equation with random input

Variance Asymptotics and Scaling Limits for Random Polytopes

Let K be a convex set in R d and let K $\lambda$ be the convex hull of a homogeneous Poisson point process P $\lambda$ of intensity $\lambda$ on K. When K is a simple polytope, we establish scaling limits as $\lambda$ $\rightarrow$ $\infty$ for the boundary of K $\lambda$ in a vicinity of a vertex of K and we give variance asymptotics for the volume and k-face functional of K $\lambda$, k $\in$ {0, 1, ..., d -- 1}, resolving an open question posed in [18]. The scaling limit of the boundary of K $\lambda$ and the variance asymptotics are described in terms of a germ-grain model consisting of cone-like grains pinned to the extreme points of a Poisson point process on R d--1 $\times$ R having intensity \sqrt de dh dhdv

Technological Capability and Productivity Growth: An Industrialized / Industrializing Country Comparison

The importance of technical change as a crucial element explaining inter-country differences in levels and rates of change in industrial productivity has been increasingly acknowledged. Hence, growing significance has been attached to developing the capability to generate such change. However, the perceived nature of that capability (described here as technological capability) and its links to productivity growth are still poorly understood. This paper empirically explores the links between (i) technological capability (the causal variable) (ii) the generation of technical changes (the intermediate variable) and (iii) productivity growth (the end-result variable). In particular, it examines organizational dimensions of technological capability. L'importance des changements techniques comme éléments clés expliquant les différences entre pays quant aux niveaux et aux taux de productivité industrielle est de plus en plus reconnue. En conséquence, il y a un intérêt croissant quant au développement des capacités nécessaires à de tels changements. Cependant, la nature de cette capacité (dite capacité technologique) et ses liens avec la croissance de productivité est encore peu comprise. Cet article explore empiriquement les liens entre (i) la capacité technologique (variable causale) (ii) la génération de changements techniques (variable intermédiaire) et (iii) la croissance de productivité (variable résultante). En particulier, il examine les dimensions organisationnelles de la capacité technologique.technological capability, organizational systems, technical change, productivity growth, pulp and paper, India, Canada, capacité technologique, systèmes organisationnels, changement technique, croissance de productivité, pâtes et papiers, Inde, Canada

Causal conditioning and instantaneous coupling in causality graphs

The paper investigates the link between Granger causality graphs recently formalized by Eichler and directed information theory developed by Massey and Kramer. We particularly insist on the implication of two notions of causality that may occur in physical systems. It is well accepted that dynamical causality is assessed by the conditional transfer entropy, a measure appearing naturally as a part of directed information. Surprisingly the notion of instantaneous causality is often overlooked, even if it was clearly understood in early works. In the bivariate case, instantaneous coupling is measured adequately by the instantaneous information exchange, a measure that supplements the transfer entropy in the decomposition of directed information. In this paper, the focus is put on the multivariate case and conditional graph modeling issues. In this framework, we show that the decomposition of directed information into the sum of transfer entropy and information exchange does not hold anymore. Nevertheless, the discussion allows to put forward the two measures as pillars for the inference of causality graphs. We illustrate this on two synthetic examples which allow us to discuss not only the theoretical concepts, but also the practical estimation issues.Comment: submitte