1,605 research outputs found
Event-based personal retrieval
People who work in a research, academic or business environment often have personal information collections which are large enough to need retrieval aids. A major difference between personal information retrieval and normal document retrieval is that the items to be retrieved are often associated with events in the searcher's life and can be retrieved by their relationship to other events as well as by content. This paper describes some of the background to event-based retrieval and then describes a prototype graphical event-based retrieval system
Power Laws and the Cosmic Ray Energy Spectrum
Two separate statistical tests are applied to the AGASA and preliminary Auger
Cosmic Ray Energy spectra in an attempt to find deviation from a pure
power-law. The first test is constructed from the probability distribution for
the maximum event of a sample drawn from a power-law. The second employs the
TP-statistic, a function defined to deviate from zero when the sample deviates
from the power-law form, regardless of the value of the power index. The AGASA
data show no significant deviation from a power-law when subjected to both
tests. Applying these tests to the Auger spectrum suggests deviation from a
power-law. However, potentially large systematics on the relative energy scale
prevent us from drawing definite conclusions at this time.Comment: 21 pages, 18 figures, submitted to Astro. Part. Phy
Electrodynamic Radiation Reaction and General Relativity
We argue that the well-known problem of the instabilities associated with the
self-forces (radiation reaction forces) in classical electrodynamics are
possibly stabilized by the introduction of gravitational forces via general
relativity
New Black Hole Solutions in Brans-Dicke Theory of Gravity
Existence check of non-trivial, stationary axisymmetric black hole solutions
in Brans-Dicke theory of gravity in different direction from those of Penrose,
Thorne and Dykla, and Hawking is performed. Namely, working directly with the
known explicit spacetime solutions in Brans-Dicke theory, it is found that
non-trivial Kerr-Newman-type black hole solutions different from general
relativistic solutions could occur for the generic Brans-Dicke parameter values
-5/2\leq \omega <-3/2. Finally, issues like whether these new black holes carry
scalar hair and can really arise in nature and if they can, what the associated
physical implications would be are discussed carefully.Comment: 20 pages, no figure, Revtex, version to appear in Phys. Rev.
Ecological model of extinctions
We present numerical results based on a simplified ecological system in
evolution, showing features of extinction similar to that claimed for the
biosystem on Earth. In the model each species consists of a population in
interaction with the others, that reproduces and evolves in time. Each species
is simultaneously a predator and a prey in a food chain. Mutations that change
the interactions are supposed to occur randomly at a low rate. Extinctions of
populations result naturally from the predator-prey dynamics. The model is not
pinned in a fitness variable, and natural selection arises from the dynamics.Comment: 16 pages (LaTeX type, RevTeX style), including 6 figures in gif
format. To be published in Phys. Rev. E (prob. Dic. 96
Persistence in higher dimensions : a finite size scaling study
We show that the persistence probability , in a coarsening system of
linear size at a time , has the finite size scaling form where is the persistence exponent and
is the coarsening exponent. The scaling function for
and is constant for large . The scaling form implies a fractal
distribution of persistent sites with power-law spatial correlations. We study
the scaling numerically for Glauber-Ising model at dimension to 4 and
extend the study to the diffusion problem. Our finite size scaling ansatz is
satisfied in all these cases providing a good estimate of the exponent
.Comment: 4 pages in RevTeX with 6 figures. To appear in Phys. Rev.
Theoretical approach and impact of correlations on the critical packet generation rate in traffic dynamics on complex networks
Using the formalism of the biased random walk in random uncorrelated networks
with arbitrary degree distributions, we develop theoretical approach to the
critical packet generation rate in traffic based on routing strategy with local
information. We explain microscopic origins of the transition from the flow to
the jammed phase and discuss how the node neighbourhood topology affects the
transport capacity in uncorrelated and correlated networks.Comment: 6 pages, 5 figure
Node-weighted measures for complex networks with spatially embedded, sampled, or differently sized nodes
When network and graph theory are used in the study of complex systems, a
typically finite set of nodes of the network under consideration is frequently
either explicitly or implicitly considered representative of a much larger
finite or infinite region or set of objects of interest. The selection
procedure, e.g., formation of a subset or some kind of discretization or
aggregation, typically results in individual nodes of the studied network
representing quite differently sized parts of the domain of interest. This
heterogeneity may induce substantial bias and artifacts in derived network
statistics. To avoid this bias, we propose an axiomatic scheme based on the
idea of node splitting invariance to derive consistently weighted variants of
various commonly used statistical network measures. The practical relevance and
applicability of our approach is demonstrated for a number of example networks
from different fields of research, and is shown to be of fundamental importance
in particular in the study of spatially embedded functional networks derived
from time series as studied in, e.g., neuroscience and climatology.Comment: 21 pages, 13 figure
Moments of the Virtual Photon Structure Function
The photon structure function is a useful testing ground for QCD. It is
perturbatively computable apart from a contribution from what is usually called
the hadronic component of the photon. There have been many proposals for this
nonperturbative part of the real photon structure function. By studying moments
of the virtual photon structure function, we explore the extent to which these
proposed nonperturbative contributions can be identified experimentally.Comment: LaTeX, 16 pages + 14 compressed and uuencoded postscript figures,
UMN-TH-1111/9
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