1,118 research outputs found
Logarithmic roughening in a growth process with edge evaporation
Roughening transitions are often characterized by unusual scaling properties.
As an example we investigate the roughening transition in a solid-on-solid
growth process with edge evaporation [Phys. Rev. Lett. 76, 2746 (1996)], where
the interface is known to roughen logarithmically with time. Performing
high-precision simulations we find appropriate scaling forms for various
quantities. Moreover we present a simple approximation explaining why the
interface roughens logarithmically.Comment: revtex, 6 pages, 7 eps figure
Long-range epidemic spreading with immunization
We study the phase transition between survival and extinction in an epidemic
process with long-range interactions and immunization. This model can be viewed
as the well-known general epidemic process (GEP) in which nearest-neighbor
interactions are replaced by Levy flights over distances r which are
distributed as P(r) ~ r^(-d-sigma). By extensive numerical simulations we
confirm previous field-theoretical results obtained by Janssen et al. [Eur.
Phys. J. B7, 137 (1999)].Comment: LaTeX, 14 pages, 4 eps figure
An Exploration of Cultural Factors Affecting Use of Communities of Practice
On-line communities of practice are potentially powerful social learning networks that can improve organizational performance. Unfortunately, administrators of on-line communities of practice report that community members do not take full advantage of this potential. This study used Shaw and Tuggle\u27s (2003) factors of knowledge management (KM) culture affecting organizational acceptance of a knowledge management initiative to explore this issue. It was hypothesized that respondents whose communities of practice possessed higher average community use per member would rate KM culture variables higher than respondents whose communities possessed a lower average community use. An analysis of survey data collected from Air Force Knowledge Now communities of practice identified two KM culture variables with a significant relationship between how individuals rated their community on each KM culture variable and use
Multifractal current distribution in random diode networks
Recently it has been shown analytically that electric currents in a random
diode network are distributed in a multifractal manner [O. Stenull and H. K.
Janssen, Europhys. Lett. 55, 691 (2001)]. In the present work we investigate
the multifractal properties of a random diode network at the critical point by
numerical simulations. We analyze the currents running on a directed
percolation cluster and confirm the field-theoretic predictions for the scaling
behavior of moments of the current distribution. It is pointed out that a
random diode network is a particularly good candidate for a possible
experimental realization of directed percolation.Comment: RevTeX, 4 pages, 5 eps figure
Maximal Localisation in the Presence of Minimal Uncertainties in Positions and Momenta
Small corrections to the uncertainty relations, with effects in the
ultraviolet and/or infrared, have been discussed in the context of string
theory and quantum gravity. Such corrections lead to small but finite minimal
uncertainties in position and/or momentum measurements. It has been shown that
these effects could indeed provide natural cutoffs in quantum field theory. The
corresponding underlying quantum theoretical framework includes small
`noncommutative geometric' corrections to the canonical commutation relations.
In order to study the full implications on the concept of locality it is
crucial to find the physical states of then maximal localisation. These states
and their properties have been calculated for the case with minimal
uncertainties in positions only. Here we extend this treatment, though still in
one dimension, to the general situation with minimal uncertainties both in
positions and in momenta.Comment: Latex, 21 pages, 2 postscript figure
Matrix Product Eigenstates for One-Dimensional Stochastic Models and Quantum Spin Chains
We show that all zero energy eigenstates of an arbitrary --state quantum
spin chain Hamiltonian with nearest neighbor interaction in the bulk and single
site boundary terms, which can also describe the dynamics of stochastic models,
can be written as matrix product states. This means that the weights in these
states can be expressed as expectation values in a Fock representation of an
algebra generated by operators fulfilling quadratic relations which
are defined by the Hamiltonian.Comment: 11 pages, Late
Temperature monitoring of metal oxide surge arresters
Varistor overtemperature above the ambient is an important state parameter of metal oxide surge arresters. The temperature monitoring using passive SAW sensors enables realisation of a surge counter function, an energy monitor, monitoring of electrical ageing and pollution stress. For temperature measurements during pollution tests of metal oxide arresters the not so advanced, TINY TALK sensors could be used. This method of temperature measurement was also applied in the field for temperature control of arresters tested at the pollution station near Głogów, Poland. The preliminary results during the first year of monitoring are presented and compared with results of similar measurements conducted in Germany close to the seacoast
On the predictive power of Local Scale Invariance
Local Scale Invariance (LSI) is a theory for anisotropic critical phenomena
designed in the spirit of conformal invariance. For a given representation of
its generators it makes non-trivial predictions about the form of universal
scaling functions. In the past decade several representations have been
identified and the corresponding predictions were confirmed for various
anisotropic critical systems. Such tests are usually based on a comparison of
two-point quantities such as autocorrelation and response functions. The
present work highlights a potential problem of the theory in the sense that it
may predict any type of two-point function. More specifically, it is argued
that for a given two-point correlator it is possible to construct a
representation of the generators which exactly reproduces this particular
correlator. This observation calls for a critical examination of the predictive
content of the theory.Comment: 17 pages, 2 eps figure
- …