783 research outputs found
Topological properties and fractal analysis of recurrence network constructed from fractional Brownian motions
Many studies have shown that we can gain additional information on time
series by investigating their accompanying complex networks. In this work, we
investigate the fundamental topological and fractal properties of recurrence
networks constructed from fractional Brownian motions (FBMs). First, our
results indicate that the constructed recurrence networks have exponential
degree distributions; the relationship between and of recurrence networks decreases with the Hurst
index of the associated FBMs, and their dependence approximately satisfies
the linear formula . Moreover, our numerical results of
multifractal analysis show that the multifractality exists in these recurrence
networks, and the multifractality of these networks becomes stronger at first
and then weaker when the Hurst index of the associated time series becomes
larger from 0.4 to 0.95. In particular, the recurrence network with the Hurst
index possess the strongest multifractality. In addition, the
dependence relationships of the average information dimension on the Hurst index can also be
fitted well with linear functions. Our results strongly suggest that the
recurrence network inherits the basic characteristic and the fractal nature of
the associated FBM series.Comment: 25 pages, 1 table, 15 figures. accepted by Phys. Rev.
Correlation entropy of synaptic input-output dynamics
The responses of synapses in the neocortex show highly stochastic and
nonlinear behavior. The microscopic dynamics underlying this behavior, and its
computational consequences during natural patterns of synaptic input, are not
explained by conventional macroscopic models of deterministic ensemble mean
dynamics. Here, we introduce the correlation entropy of the synaptic
input-output map as a measure of synaptic reliability which explicitly includes
the microscopic dynamics. Applying this to experimental data, we find that
cortical synapses show a low-dimensional chaos driven by the natural input
pattern.Comment: 7 pages, 6 Figures (7 figure files
Granger Causality and Cross Recurrence Plots in Rheochaos
Our stress relaxation measurements on wormlike micelles using a Rheo-SALS
(rheology + small angle light scattering) apparatus allow simultaneous
measurements of the stress and the scattered depolarised intensity. The latter
is sensitive to orientational ordering of the micelles. To determine the
presence of causal influences between the stress and the depolarised intensity
time series, we have used the technique of linear and nonlinear Granger
causality. We find there exists a feedback mechanism between the two time
series and that the orientational order has a stronger causal effect on the
stress than vice versa. We have also studied the phase space dynamics of the
stress and the depolarised intensity time series using the recently developed
technique of cross recurrence plots (CRPs). The presence of diagonal line
structures in the CRPs unambiguously proves that the two time series share
similar phase space dynamics.Comment: 10 pages, 7 figure
On the fraction of dark matter in charged massive particles (CHAMPs)
From various cosmological, astrophysical and terrestrial requirements, we
derive conservative upper bounds on the present-day fraction of the mass of the
Galactic dark matter (DM) halo in charged massive particles (CHAMPs). If dark
matter particles are neutral but decay lately into CHAMPs, the lack of
detection of heavy hydrogen in sea water and the vertical pressure equilibrium
in the Galactic disc turn out to put the most stringent bounds. Adopting very
conservative assumptions about the recoiling velocity of CHAMPs in the decay
and on the decay energy deposited in baryonic gas, we find that the lifetime
for decaying neutral DM must be > (0.9-3.4)x 10^3 Gyr. Even assuming the
gyroradii of CHAMPs in the Galactic magnetic field are too small for halo
CHAMPs to reach Earth, the present-day fraction of the mass of the Galactic
halo in CHAMPs should be < (0.4-1.4)x 10^{-2}. We show that redistributing the
DM through the coupling between CHAMPs and the ubiquitous magnetic fields
cannot be a solution to the cuspy halo problem in dwarf galaxies.Comment: 21 pages, 2 figures. To appear in JCA
The KLN Theorem and Soft Radiation in Gauge Theories: Abelian Case
We present a covariant formulation of the Kinoshita, Lee, Nauenberg (KLN)
theorem for processes involving the radiation of soft particles. The role of
the disconnected diagrams is explored and a rearrangement of the perturbation
theory is performed such that the purely disconnected diagrams are factored
out. The remaining effect of the disconnected diagrams results in a simple
modification of the usual Feynman rules for the S-matrix elements. As an
application, we show that when combined with the Low theorem, this leads to a
proof of the absense of the corrections to inclusive processes (like the
Drell-Yan process). In this paper the abelian case is discussed to all orders
in the coupling.Comment: 27 pages, LaTeX, 14 figure
Recurrence quantification analysis as a tool for the characterization of molecular dynamics simulations
A molecular dynamics simulation of a Lennard-Jones fluid, and a trajectory of
the B1 immunoglobulin G-binding domain of streptococcal protein G (B1-IgG)
simulated in water are analyzed by recurrence quantification, which is
noteworthy for its independence from stationarity constraints, as well as its
ability to detect transients, and both linear and nonlinear state changes. The
results demonstrate the sensitivity of the technique for the discrimination of
phase sensitive dynamics. Physical interpretation of the recurrence measures is
also discussed.Comment: 7 pages, 8 figures, revtex; revised for review for Phys. Rev. E
(clarifications and expansion of discussion)-- addition of the 8 postscript
figures previously omitted, but unchanged from version
Recurrence Plot Based Measures of Complexity and its Application to Heart Rate Variability Data
The knowledge of transitions between regular, laminar or chaotic behavior is
essential to understand the underlying mechanisms behind complex systems. While
several linear approaches are often insufficient to describe such processes,
there are several nonlinear methods which however require rather long time
observations. To overcome these difficulties, we propose measures of complexity
based on vertical structures in recurrence plots and apply them to the logistic
map as well as to heart rate variability data. For the logistic map these
measures enable us not only to detect transitions between chaotic and periodic
states, but also to identify laminar states, i.e. chaos-chaos transitions. The
traditional recurrence quantification analysis fails to detect the latter
transitions. Applying our new measures to the heart rate variability data, we
are able to detect and quantify the laminar phases before a life-threatening
cardiac arrhythmia occurs thereby facilitating a prediction of such an event.
Our findings could be of importance for the therapy of malignant cardiac
arrhythmias
The Interstellar Environment of our Galaxy
We review the current knowledge and understanding of the interstellar medium
of our galaxy. We first present each of the three basic constituents - ordinary
matter, cosmic rays, and magnetic fields - of the interstellar medium, laying
emphasis on their physical and chemical properties inferred from a broad range
of observations. We then position the different interstellar constituents, both
with respect to each other and with respect to stars, within the general
galactic ecosystem.Comment: 39 pages, 12 figures (including 3 figures in 2 parts
Scaling Patterns for QCD Jets
Jet emission at hadron colliders follows simple scaling patterns. Based on
perturbative QCD we derive Poisson and staircase scaling for final state as
well as initial state radiation. Parton density effects enhance staircase
scaling at low multiplicities. We propose experimental tests of our theoretical
findings in Z+jets and QCD gap jets production based on minor additions to
current LHC analyses.Comment: 36 pages, 16 figure
Nonthermal Emission from Star-Forming Galaxies
The detections of high-energy gamma-ray emission from the nearby starburst
galaxies M82 & NGC253, and other local group galaxies, broaden our knowledge of
star-driven nonthermal processes and phenomena in non-AGN star-forming
galaxies. We review basic aspects of the related processes and their modeling
in starburst galaxies. Since these processes involve both energetic electrons
and protons accelerated by SN shocks, their respective radiative yields can be
used to explore the SN-particle-radiation connection. Specifically, the
relation between SN activity, energetic particles, and their radiative yields,
is assessed through respective measures of the particle energy density in
several star-forming galaxies. The deduced energy densities range from O(0.1)
eV/cm^3 in very quiet environments to O(100) eV/cm^3 in regions with very high
star-formation rates.Comment: 17 pages, 5 figures, to be published in Astrophysics and Space
Science Proceeding
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