36,240 research outputs found
Network traffic behaviour near phase transition point
We explore packet traffic dynamics in a data network model near phase
transition point from free flow to congestion. The model of data network is an
abstraction of the Network Layer of the OSI (Open Systems Interconnection)
Reference Model of packet switching networks. The Network Layer is responsible
for routing packets across the network from their sources to their destinations
and for control of congestion in data networks. Using the model we investigate
spatio-temporal packets traffic dynamics near the phase transition point for
various network connection topologies, and static and adaptive routing
algorithms. We present selected simulation results and analyze them
Individual-based lattice model for spatial spread of epidemics
We present a lattice gas cellular automaton (LGCA) to study spatial and
temporal dynamics of an epidemic of SIR (susceptible-infected-removed) type.
The automaton is fully discrete, i.e. space, time and number of individuals are
discrete variables. The automaton can be applied to study spread of epidemics
in both human and animal populations. We investigate effects of spatial
inhomogeneities in initial distribution of infected and vaccinated populations
on the dynamics of epidemic of SIR type. We discuss vaccination strategies
which differ only in spatial distribution of vaccinated individuals. Also, we
derive an approximate, mean-field type description of the automaton, and
discuss differences between the mean-field dynamics and the results of LGCA
simulation.Comment: 13 pages, 5 figure
Integrality of quantum 3-manifold invariants and rational surgery formula
We prove that the Witten-Reshetikhin-Turaev (WRT) SO(3) invariant of an
arbitrary 3-manifold M is always an algebraic integer. Moreover, we give a
rational surgery formula for the unified invariant dominating WRT SO(3)
invariants of rational homology 3-spheres at roots of unity of order co-prime
with the torsion. As an application, we compute the unified invariant for
Seifert fibered spaces and for Dehn surgeries on twist knots. We show that this
invariant separates integral homology Seifert fibered spaces and can be used to
detect the unknot.Comment: 18 pages, Compositio Math. in pres
Building on a Solid Baseline: Anticipatory Biases in Attention.
A brain-imaging paper by Kastner and colleagues in 1999 was the first to demonstrate that merely focusing attention at a spatial location changed the baseline activity level in various regions of human visual cortex even before any stimuli appeared. The study provided a touchstone for investigating cognitive-sensory interactions and understanding the proactive endogenous signals that shape perception
Structure of the QCD Vacuum As Seen By Lattice Simulations
This talk is a review of our studies of instantons and their properties as
seen in our lattice simulations of SU(2) gauge theory. We have measured the
topological susceptibility and the size distribution of instantons in the QCD
vacuum.
We have also investigated the properties of quarks moving in instanton
background field configurations, where the sizes and locations of the
instantons are taken from simulations of the full gauge theory. By themselves,
these multi-instanton configurations do not confine quarks, but they induce
chiral symmetry breaking.Comment: 18 pages, LaTeX, 8 figures, uses epsf, Talk given at YKIS9
Universal contact for a Tonks-Girardeau gas at finite temperature
We determine the finite-temperature momentum distribution of a strongly
interacting 1D Bose gas in the Tonks-Girardeau (impenetrable-boson) limit under
harmonic confinement, and explore its universal properties associated to the
scale invariance of the model. We show that, at difference from the unitary
Fermi gas in three dimensions, the weight of its large-momentum tails -- given
by the Tan's contact -- increase with temperature, and calculate the
high-temperature universal second contact coefficient using a virial expansion.Comment: 6 pages, 2 figure
Effects of population mixing on the spread of SIR epidemics
We study dynamics of spread of epidemics of SIR type in a realistic
spatially-explicit geographical region, Southern and Central Ontario, using
census data obtained from Statistics Canada, and examine the role of population
mixing in epidemic processes. Our model incorporates the random nature of
disease transmission, the discreteness and heterogeneity of distribution of
host population. We find that introduction of a long-range interaction destroys
spatial correlations very easily if neighbourhood sizes are homogeneous. For
inhomogeneous neighbourhoods, very strong long-range coupling is required to
achieve a similar effect. Our work applies to the spread of in influenza during
a single season and our model is applicable to other geographic regions, if
suitable data is available
Estimating the Indirect Gaming Contribution of Bingo Rooms
Using data from two repeater market hotel casinos, the relationship between bingo and slot business volumes is explored. Contrary to conjecture supplied by industry executives, the results fail to demonstrate a statistically significant relationship between daily bingo headcount and coin-in. This result was found in three different analyses, including one· attempt to estimate the impact of bingo headcount on low-denomination coin-in. This study advances the literature by challenging the assumption that bingo rooms produce substantial indirect slot profits. Given the minimal direct contribution to property cash flows, if any, the results suggest that bingo rooms are not always the highest and best use of valuable casino floor space
Unified quantum invariants and their refinements for homology 3-spheres with 2-torsion
For every rational homology 3-sphere with 2-torsion only we construct a
unified invariant (which takes values in a certain cyclotomic completion of a
polynomial ring), such that the evaluation of this invariant at any odd root of
unity provides the SO(3) Witten-Reshetikhin-Turaev invariant at this root and
at any even root of unity the SU(2) quantum invariant. Moreover, this unified
invariant splits into a sum of the refined unified invariants dominating spin
and cohomological refinements of quantum SU(2) invariants. New results on the
Ohtsuki series and the integrality of quantum invariants are the main
applications of our construction.Comment: 23 pages, results of math.QA/0510382 are include
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