Canonical ``Loop'' Quantum Gravity and Spin Foam Models

The canonical ``loop'' formulation of quantum gravity is a mathematically well defined, background independent, non perturbative standard quantization of Einstein's theory of General Relativity. Some among the most meaningful results of the theory are: 1) the complete calculation of the spectrum of geometric quantities like the area and the volume and the consequent physical predictions about the structure of the space-time at the Plank scale; 2) a microscopical derivation of the Bekenstein-Hawking black-hole entropy formula. Unfortunately, despite recent results, the dynamical aspect of the theory (imposition of the Wheller-De Witt constraint) remains elusive. After a short description of the basic ideas and the main results of loop quantum gravity we show in which sence the exponential of the super Hamiltonian constraint leads to the concept of spin foam and to a four dimensional formulation of the theory. Moreover, we show that some topological field theories as the BF theory in 3 and 4 dimension admits a spin foam formulation. We argue that the spin-foams/spin-networks formalism it is the natural framework to discuss loop quantum gravity and topological field theory.Comment: 17 pages, LaTeX2e, 7 figures. To appear in the proceeding of the XXIII SIGRAV conference, Monopoli (ITALY), September 21st-25th, 1998. Minor correction

Change, psychosocial stress and health in an era of globalization

In the last decades, globalization has produced an acceleration of social, economic and political changes worldwide. These changes had a number of positive effects including enhancing political freedom, living standards and health conditions. However, many of them have also produced adverse health consequences, especially when they have been implemented in a sudden, rapid and unexpected way. This is especially true among those populations whose ability to adjust to the new circumstances generated by rapid change was limited. The aim of the present research project was to examine the health consequences of rapid social, economic and political change following globalization as well as to investigate the role of psychosocial factors in explaining these relationships. A theoretical framework proposing major psychosocial pathways connecting rapid change with health-related outcomes has been developed. A series of case studies from countries affected by rapid change supported the hypothesized relationships included in the framework. Countries of interest were the former Soviet Union nations, China, Japan, Micronesia Islands, New Zealand, Australia, Canada, and the United States. The limited ability of certain populations to adjust to rapid changes induced by globalization as well as the pace of change of social, economic and political reforms are discussed

Differences in forecasting approaches between product firms and product-service systems (PSS)

This paper examines the forecasting implications for Product-Service Systems (PSS) applications in manufacturing firms. The approach taken is to identify the scope of operations for PSS applications by identifying all the activities associated with the total cost of ownership (TCO). The paper then develops a revenue model for manufacturing firms providing PSS applications. The revenue model identifies three generic revenue streams that provide the basis for discussion on the differences in forecasting approaches between product firms and Product-Service Systems (PSS) in manufacturing firms. The forecasting approaches are different due to the nature of customer involvement in the service aspect of PSS applications. This necessitates an understanding of the customer service experience and the factors affecting this such as the service profit chain which links profitability, customer loyalty and service value to employee satisfaction, capability and productivity. The forecasting approaches identified raises forecasting challenges for each of the three generic revenue sources. These challenges vary from the difficulty in obtaining the service user’s viewpoint through to difficulties in determining market acceptance of PSS applications

Stellar Distributions and NIR Colours of Normal Galaxies

We discuss some results of a morphological study of edge-on galaxies, based on optical and especially near-infrared surface photometry. We find that the vertical surface brightness distributions of galaxies are fitted very well by exponential profiles, much better than by isothermal distributions. We find that in general the vertical scale height increases when going outward. This increase is strong for early-type spiral galaxies and very small for late types. We argue that it can be due to the presence of thick discs with scale lengths larger than the galaxy's main disc. Finally we discuss the colour-magnitude relation in I-K for spiral galaxies. We find that it is a tight relation, for which the scatter is similar to the observational uncertainties, with a steeper slope than for elliptical galaxies.Comment: Invited review, to appear in "Extragalactic Astronomy in the Infrared", eds. G.A. Mamon, Trinh Xuan Thuan, and J. Tran Thanh Van, Editions Frontieres, Gif-sur-Yvette. LaTeX2e, 10 pages, 6 postscript figures and moriond.sty included. See also ftp://kapteyn.astro.rug.nl/peletier/lesarcs.ps.g

Photoelectric charging of partially sunlit dielectric surfaces in space

Sunlight-shadow effects may substantially alter the charging situation for a dielectric surface. The sunlight-shadow boundary tends to be the site of intense multipole electric fields. Charges on a sunlit dielectric surface have a finite effective mobility. The charge distribution tends to resemble that on a conducting surface. A boundary between a conducting and a dielectric surface may not represent a conductivity discontinuity when this boundary is sunlit; charges may migrate at a nontrivial rate across the boundary. A contracting or expanding sunlit area may experience a supercharging

Reply to ``Comment on `On the inconsistency of the Bohm-Gadella theory with quantum mechanics'''

In this reply, we show that when we apply standard distribution theory to the Lippmann-Schwinger equation, the resulting spaces of test functions would comply with the Hardy axiom only if classic results of Paley and Wiener, of Gelfand and Shilov, and of the theory of ultradistributions were wrong. As well, we point out several differences between the ``standard method'' of constructing rigged Hilbert spaces in quantum mechanics and the method used in Time Asymmetric Quantum Theory.Comment: 13 page