137 research outputs found
Understanding the temperature and the chemical potential using computer simulations
Several Monte Carlo algorithms and applications that are useful for
understanding the concepts of temperature and chemical potential are discussed.
We then introduce a generalization of the demon algorithm that measures the
chemical potential and is suitable for simulating systems with variable
particle number.Comment: 23 pages including 6 figure
Teaching statistical physics by thinking about models and algorithms
We discuss several ways of illustrating fundamental concepts in statistical
and thermal physics by considering various models and algorithms. We emphasize
the importance of replacing students' incomplete mental images by models that
are physically accurate. In some cases it is sufficient to discuss the results
of an algorithm or the behavior of a model rather than having students write a
program.Comment: 21 pages, 4 figures, submitted to the American Journal of Physic
Recognition of Emerging Technology Trends. Class-selective study of citations in the U.S. Patent Citation Network
By adopting a citation-based recursive ranking method for patents the
evolution of new fields of technology can be traced. Specifically, it is
demonstrated that the laser / inkjet printer technology emerged from the
recombination of two existing technologies: sequential printing and static
image production. The dynamics of the citations coming from the different
"precursor" classes illuminates the mechanism of the emergence of new fields
and give the possibility to make predictions about future technological
development. For the patent network the optimal value of the PageRank damping
factor is close to 0.5; the application of d=0.85 leads to unacceptable ranking
results.Comment: 8 pages, 2 tables, 1 figure , (accepted). in Scientometrics 201
Is Random Close Packing of Spheres Well Defined?
Despite its long history, there are many fundamental issues concerning random
packings of spheres that remain elusive, including a precise definition of
random close packing (RCP). We argue that the current picture of RCP cannot be
made mathematically precise and support this conclusion via a molecular
dynamics study of hard spheres using the Lubachevsky-Stillinger compression
algorithm. We suggest that this impasse can be broken by introducing the new
concept of a maximally random jammed state, which can be made precise.Comment: 6 pages total, 2 figure
The 2D XY model on a finite lattice with structural disorder: quasi-long-range ordering under realistic conditions
We present an analytic approach to study concurrent influence of quenched
non-magnetic site-dilution and finiteness of the lattice on the 2D XY model.
Two significant deeply connected features of this spin model are: a special
type of ordering (quasi-long-range order) below a certain temperature and a
size-dependent mean value of magnetisation in the low-temperature phase that
goes to zero (according to the Mermin-Wagner-Hohenberg theorem) in the
thermodynamic limit. We focus our attention on the asymptotic behaviour of the
spin-spin correlation function and the probability distribution of
magnetisation. The analytic approach is based on the spin-wave approximation
valid for the low-temperature regime and an expansion in the parameters which
characterise the deviation from completely homogeneous configuration of
impurities. We further support the analytic considerations by Monte Carlo
simulations performed for different concentrations of impurities and compare
analytic and MC results. We present as the main quantitative result of the work
the exponent of the spin-spin correlation function power law decay. It is non
universal depending not only on temperature as in the pure model but also on
concentration of magnetic sites. This exponent characterises also the vanishing
of magnetisation with increasing lattice size.Comment: 13 pages, 7 eps figures, style files include
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