62,653 research outputs found
Luminosity segregation versus fractal scaling in the galaxy distribution
In this letter I present results from a correlation analysis of three galaxy
redshift catalogs: the SSRS2, the CfA2 and the PSCz. I will focus on the
observation that the amplitude of the two--point correlation function rises if
the depth of the sample is increased. There are two competing explanations for
this observation, one in terms of a fractal scaling, the other based on
luminosity segregation. I will show that there is strong evidence that the
observed growth is due to a luminosity dependent clustering of the galaxies.Comment: 7 pages, EPL in pres
Modeling and simulating chemical reactions
Many students are familiar with the idea of modeling chemical reactions in terms of ordinary differential equations. However, these deterministic reaction rate equations are really a certain large-scale limit of a sequence of finer-scale probabilistic models. In studying this hierarchy of models, students can be exposed to a range of modern ideas in applied and computational mathematics. This article introduces some of the basic concepts in an accessible manner and points to some challenges that currently occupy researchers in this area. Short, downloadable MATLAB codes are listed and described
Drastic disorded-induced reduction of signal amplification in scale-free networks
Understanding information transmission across a network is a fundamental task
for controlling and manipulating both biological and man-made information
processing systems. Here, we show how topological resonant-like amplification
effects in scale-free networks of signaling devices are drastically reduced
when phase disorder in the external signals is considered. This is demonstrated
theoretically by means of a star-like network of overdamped bistable systems,
and confirmed numerically by simulations of scale-free networks of such
systems. The taming effect of the phase disorder is found to be sensitive to
the amplification's strength, while the topology-induced amplification
mechanism is robust against this kind of quenched disorder in the sense that it
does not significantly change the values of the coupling strength where
amplification is maximum in its absence.Comment: 5 pages, 4 (double) figure
Spatial storage of discrete dark solitons
The interaction between a mobile discrete dark soliton (DDS) and impurities
in one-dimensional nonlinear (Kerr) photonic lattices is studied. We found that
the scattering is an inelastic process where the DDS can be reflected or
transmitted depending on its transversal speed and the strength of the
impurities. In particular, in the reflection regime, the DDS increases its
transversal speed after each scattering. A method for spatial storage of DDS
solutions using two impurities is discussed, where the soliton can be trapped
within a storage region until it reaches the critical speed needed to be
transmitted. We show, numerically, that this method allows the storage of
multiple DDS simultaneously.Comment: 6 pages and 6 figure
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