A unified framework for Schelling's model of segregation

Schelling's model of segregation is one of the first and most influential models in the field of social simulation. There are many variations of the model which have been proposed and simulated over the last forty years, though the present state of the literature on the subject is somewhat fragmented and lacking comprehensive analytical treatments. In this article a unified mathematical framework for Schelling's model and its many variants is developed. This methodology is useful in two regards: firstly, it provides a tool with which to understand the differences observed between models; secondly, phenomena which appear in several model variations may be understood in more depth through analytic studies of simpler versions.Comment: 21 pages, 3 figure

European community internal market technical legislation - a critical review of the processes in the context of the free movement of goods

This research project was initiated in response to concerns held by the author on aspects of the European Community (EC) internal market. These concerns applied particularly to what was understood at the time to be the perceptions of EC internal market practitioners; their perceptions on the process of EC internal market technical legislative change and on how well the EC internal market was functioning. A literature review was undertaken to determine if, and if so where, the EC internal market technical legislative change process was defined and to determine which organisations were the important players in the process. The literature review was then extended to determine more about the players in the process and the information exchanges between the defined process and individuals, such as EC internal market practitioners, having a legitimate interest in the process. Also within the literature review the views of other commentators are noted and assessed. A methodological review was undertaken. This review gave rise to the formulation of a structured interview that was applied to a purposive sample of EC internal market practitioners. Two main areas were examined via the structured interview. The first was the knowledge of the overall EC internal market technical legislative change process and of its main players. The second area was the perception of the completeness of the functioning of the EC internal market possessed by EC internal market practitioners. This research concludes that there are a number of flaws in the treaty establishing the European Community; this is the treaty that includes the high level description of the EC internal market technical legislative process. One of these flaws particularly affects the EC internal market technical legislative process. The research also concludes that the application of the treaty is not consistent and that the knowledge of the EC internal market technical legislative process exhibited by EC internal market practitioners is poor. Based on the conclusions a number of recommendations are made

Multiple Hard Partonic Collisions with Correlations in Proton-Proton Scattering

We propose a simple method for incorporating correlations into the impact parameter space description of multiple (semi-)hard partonic collisions in high energy hadron-hadron scattering. The perturbative QCD input is the standard factorization theorem for inclusive dijet production with a lower cutoff on transverse momentum. The width of the transverse distribution of hard partons is fixed by parameterizations of the two-gluon form factor. We then reconstruct the hard contribution to the total inelastic profile function and obtain corrections due to correlations to the more commonly used eikonal description. Estimates of the size of double correlation corrections are based on the rate of double collisions measured at the Tevatron. We find that, if typical values for the lower transverse momentum cutoff are used in the calculation of the inclusive hard dijet cross section, then the correlation corrections are necessary for maintaining consistency with expectations for the total inelastic proton-proton cross section at LHC energies.Comment: Typos fixed, Figures 2,9 and 10 added, matches version published in Phys. Rev.

Observational signatures of convectively driven waves in massive stars

We demonstrate observational evidence for the occurrence of convectively driven internal gravity waves (IGW) in young massive O-type stars observed with high-precision CoRoT space photometry. This evidence results from a comparison between velocity spectra based on 2D hydrodynamical simulations of IGW in a differentially-rotating massive star and the observed spectra.We also show that the velocity spectra caused by IGW may lead to detectable line-profile variability and explain the occurrence of macroturbulence in the observed line profiles of OB stars. Our findings provide predictions that can readily be tested by including a sample of bright slowly and rapidly rotating OB-type stars in the scientific programme of the K2 mission accompanied by high-precision spectroscopy and their confrontation with multi-dimensional hydrodynamic simulations of IGW for various masses and ages.Comment: 4 pages, 3 figures, accepted for publication in The Astrophysical Journal Letter