5,174 research outputs found
Self-organized Criticality on Small World Networks
We study the BTW-height model of self-organized criticality on a square
lattice with some long range connections giving to the lattice the character of
small world network. We find that as function of the fraction of long
ranged bonds the power law of the avalanche size and lifetime distribution
changes following a crossover scaling law with crossover exponents 2/3 and 1
for size and lifetime respectively.Comment: 7 figure
A remark on the Brylinski conjecture for orbifolds
We present reformulation of Mathieu's result on representing cohomology
classes of symplectic manifold with symplectically harmonic forms. We apply it
to the case of foliated manifolds with transversally symplectic structure and
to symplectic orbifolds. We obtain in particular that such representation is
always possible for compact K\"{a}hler orbifolds.Comment: 10 page
Different hierarchy of avalanches observed in the Bak-Sneppen evolution model
We introduce a new quantity, average fitness, into the Bak-Sneppen evolution
model. Through the new quantity, a different hierarchy of avalanches is
observed. The gap equation, in terms of the average fitness, is presented to
describe the self-organization of the model. It is found that the critical
value of the average fitness can be exactly obtained. Based on the simulations,
two critical exponents, avalanche distribution and avalanche dimension, of the
new avalanches are given.Comment: 5 pages, 3 figure
Galilean noncommutative gauge theory: symmetries & vortices
Noncommutative Chern-Simons gauge theory coupled to nonrelativistic scalars
or spinors is shown to admit the ``exotic'' two-parameter-centrally extended
Galilean symmetry, realized in a unique way consistent with the Seiberg-Witten
map. Nontopological spinor vortices and topological external-field vortices are
constructed by reducing the problem to previously solved self-dual equations.Comment: Updated version: some statements rephrased and further references
added. LaTex, 17 pages, no figure
The Homogeneous Broadcast Problem in Narrow and Wide Strips
Let be a set of nodes in a wireless network, where each node is modeled
as a point in the plane, and let be a given source node. Each node
can transmit information to all other nodes within unit distance, provided
is activated. The (homogeneous) broadcast problem is to activate a minimum
number of nodes such that in the resulting directed communication graph, the
source can reach any other node. We study the complexity of the regular and
the hop-bounded version of the problem (in the latter, must be able to
reach every node within a specified number of hops), with the restriction that
all points lie inside a strip of width . We almost completely characterize
the complexity of both the regular and the hop-bounded versions as a function
of the strip width .Comment: 50 pages, WADS 2017 submissio
Turbulent self-organized criticality
In the prototype sandpile model of self-organized criticality time series
obtained by decomposing avalanches into waves of toppling show intermittent
fluctuations. The q-th moments of wave size differences possess local
multiscaling and global simple scaling regimes analogous to those holding for
velocity structure functions in fluid turbulence. The correspondence involves
identity of a basic scaling relation and of the form of relevant probability
distributions. The sandpile provides a qualitative analog of many features of
turbulent phenomena.Comment: Revised version. 5 RevTex pages and 4 postscript figure
Scaling of impact fragmentation near the critical point
We investigated two-dimensional brittle fragmentation with a flat impact
experimentally, focusing on the low impact energy region near the
fragmentation-critical point. We found that the universality class of
fragmentation transition disagreed with that of percolation. However, the
weighted mean mass of the fragments could be scaled using the pseudo-control
parameter multiplicity. The data for highly fragmented samples included a
cumulative fragment mass distribution that clearly obeyed a power-law. The
exponent of this power-law was 0.5 and it was independent of sample size. The
fragment mass distributions in this regime seemed to collapse into a unified
scaling function using weighted mean fragment mass scaling. We also examined
the behavior of higher order moments of the fragment mass distributions, and
obtained multi-scaling exponents that agreed with those of the simple biased
cascade model.Comment: 6 pages, 6 figure
The origin of power-law distributions in self-organized criticality
The origin of power-law distributions in self-organized criticality is
investigated by treating the variation of the number of active sites in the
system as a stochastic process. An avalanche is then regarded as a first-return
random walk process in a one-dimensional lattice. Power law distributions of
the lifetime and spatial size are found when the random walk is unbiased with
equal probability to move in opposite directions. This shows that power-law
distributions in self-organized criticality may be caused by the balance of
competitive interactions. At the mean time, the mean spatial size for
avalanches with the same lifetime is found to increase in a power law with the
lifetime.Comment: 4 pages in RevTeX, 3 eps figures. To appear in J.Phys.G. To appear in
J. Phys.
Crossover from Percolation to Self-Organized Criticality
We include immunity against fire as a new parameter into the self-organized
critical forest-fire model. When the immunity assumes a critical value,
clusters of burnt trees are identical to percolation clusters of random bond
percolation. As long as the immunity is below its critical value, the
asymptotic critical exponents are those of the original self-organized critical
model, i.e. the system performs a crossover from percolation to self-organized
criticality. We present a scaling theory and computer simulation results.Comment: 4 pages Revtex, two figures included, to be published in PR
The Moduli Space of Noncommutative Vortices
The abelian Higgs model on the noncommutative plane admits both BPS vortices
and non-BPS fluxons. After reviewing the properties of these solitons, we
discuss several new aspects of the former. We solve the Bogomoln'yi equations
perturbatively, to all orders in the inverse noncommutivity parameter, and show
that the metric on the moduli space of k vortices reduces to the computation of
the trace of a k-dimensional matrix. In the limit of large noncommutivity, we
present an explicit expression for this metric.Comment: Invited contribution to special issue of J.Math.Phys. on
"Integrability, Topological Solitons and Beyond"; 10 Pages, 1 Figure. v2:
revision of history in introductio
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