41,376 research outputs found
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
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
Stochastic oscillations of adaptive networks: application to epidemic modelling
Adaptive-network models are typically studied using deterministic
differential equations which approximately describe their dynamics. In
simulations, however, the discrete nature of the network gives rise to
intrinsic noise which can radically alter the system's behaviour. In this
article we develop a method to predict the effects of stochasticity in adaptive
networks by making use of a pair-based proxy model. The technique is developed
in the context of an epidemiological model of a disease spreading over an
adaptive network of infectious contact. Our analysis reveals that in this model
the structure of the network exhibits stochastic oscillations in response to
fluctuations in the disease dynamic.Comment: 11 pages, 4 figure
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