3,556 research outputs found
Assessment of long-range correlation in animal behaviour time series: the temporal pattern of locomotor activity of Japanese quail (Coturnix coturnix) and mosquito larva (Culex quinquefasciatus)
The aim of this study was to evaluate the performance of a classical method
of fractal analysis, Detrended Fluctuation Analysis (DFA), in the analysis of
the dynamics of animal behavior time series. In order to correctly use DFA to
assess the presence of long-range correlation, previous authors using
statistical model systems have stated that different aspects should be taken
into account such as: 1) the establishment by hypothesis testing of the absence
of short term correlation, 2) an accurate estimation of a straight line in the
log-log plot of the fluctuation function, 3) the elimination of artificial
crossovers in the fluctuation function, and 4) the length of the time series.
Taking into consideration these factors, herein we evaluated the presence of
long-range correlation in the temporal pattern of locomotor activity of
Japanese quail ({\sl Coturnix coturnix}) and mosquito larva ({\sl Culex
quinquefasciatus}). In our study, modeling the data with the general ARFIMA
model, we rejected the hypothesis of short range correlations (d=0) in all
cases. We also observed that DFA was able to distinguish between the artificial
crossover observed in the temporal pattern of locomotion of Japanese quail, and
the crossovers in the correlation behavior observed in mosquito larvae
locomotion. Although the test duration can slightly influence the parameter
estimation, no qualitative differences were observed between different test
durations
Tsallis non-extensive statistics, intermittent turbulence, SOC and chaos in the solar plasma. Part one: Sunspot dynamics
In this study, the nonlinear analysis of the sunspot index is embedded in the
non-extensive statistical theory of Tsallis. The triplet of Tsallis, as well as
the correlation dimension and the Lyapunov exponent spectrum were estimated for
the SVD components of the sunspot index timeseries. Also the multifractal
scaling exponent spectrum, the generalized Renyi dimension spectrum and the
spectrum of the structure function exponents were estimated experimentally and
theoretically by using the entropy principle included in Tsallis non extensive
statistical theory, following Arimitsu and Arimitsu. Our analysis showed
clearly the following: a) a phase transition process in the solar dynamics from
high dimensional non Gaussian SOC state to a low dimensional non Gaussian
chaotic state, b) strong intermittent solar turbulence and anomalous
(multifractal) diffusion solar process, which is strengthened as the solar
dynamics makes phase transition to low dimensional chaos in accordance to
Ruzmaikin, Zeleny and Milovanov studies c) faithful agreement of Tsallis non
equilibrium statistical theory with the experimental estimations of i)
non-Gaussian probability distribution function, ii) multifractal scaling
exponent spectrum and generalized Renyi dimension spectrum, iii) exponent
spectrum of the structure functions estimated for the sunspot index and its
underlying non equilibrium solar dynamics.Comment: 40 pages, 11 figure
The elusive source of quantum effectiveness
We discuss two qualities of quantum systems: various correlations existing
between their subsystems and the distingushability of different quantum states.
This is then applied to analysing quantum information processing. While quantum
correlations, or entanglement, are clearly of paramount importance for
efficient pure state manipulations, mixed states present a much richer arena
and reveal a more subtle interplay between correlations and distinguishability.
The current work explores a number of issues related with identifying the
important ingredients needed for quantum information processing. We discuss the
Deutsch-Jozsa algorithm, the Shor algorithm, the Grover algorithm and the power
of a single qubit class of algorithms. One section is dedicated to cluster
states where entanglement is crucial, but its precise role is highly
counter-intuitive. Here we see that distinguishability becomes a more useful
concept.Comment: 8 pages, no figure
The Quantum Frontier
The success of the abstract model of computation, in terms of bits, logical
operations, programming language constructs, and the like, makes it easy to
forget that computation is a physical process. Our cherished notions of
computation and information are grounded in classical mechanics, but the
physics underlying our world is quantum. In the early 80s researchers began to
ask how computation would change if we adopted a quantum mechanical, instead of
a classical mechanical, view of computation. Slowly, a new picture of
computation arose, one that gave rise to a variety of faster algorithms, novel
cryptographic mechanisms, and alternative methods of communication. Small
quantum information processing devices have been built, and efforts are
underway to build larger ones. Even apart from the existence of these devices,
the quantum view on information processing has provided significant insight
into the nature of computation and information, and a deeper understanding of
the physics of our universe and its connections with computation.
We start by describing aspects of quantum mechanics that are at the heart of
a quantum view of information processing. We give our own idiosyncratic view of
a number of these topics in the hopes of correcting common misconceptions and
highlighting aspects that are often overlooked. A number of the phenomena
described were initially viewed as oddities of quantum mechanics. It was
quantum information processing, first quantum cryptography and then, more
dramatically, quantum computing, that turned the tables and showed that these
oddities could be put to practical effect. It is these application we describe
next. We conclude with a section describing some of the many questions left for
future work, especially the mysteries surrounding where the power of quantum
information ultimately comes from.Comment: Invited book chapter for Computation for Humanity - Information
Technology to Advance Society to be published by CRC Press. Concepts
clarified and style made more uniform in version 2. Many thanks to the
referees for their suggestions for improvement
Oscillations in the Primordial Bispectrum: Mode Expansion
We consider the presence of oscillations in the primordial bispectrum,
inspired by three different cosmological models; features in the primordial
potential, resonant type non-Gaussianities and deviation from the standard
Bunch Davies vacuum. In order to put constraints on their bispectra, a logical
first step is to put these into factorized form which can be achieved via the
recently proposed method of polynomial basis expansion on the tetrahedral
domain. We investigate the viability of such an expansion for the oscillatory
bispectra and find that one needs an increasing number of orthonormal mode
functions to achieve significant correlation between the expansion and the
original spectrum as a function of their frequency. To reduce the number of
modes required, we propose a basis consisting of Fourier functions
orthonormalized on the tetrahedral domain. We show that the use of Fourier mode
functions instead of polynomial mode functions can lead to the necessary
factorizability with the use of only 1/5 of the total number of modes required
to reconstruct the bispectra with polynomial mode functions. Moreover, from an
observational perspective, the expansion has unique signatures depending on the
orientation of the oscillation due to a resonance effect between the mode
functions and the original spectrum. This effect opens the possibility to
extract informa- tion about both the frequency of the bispectrum as well as its
shape while considering only a limited number of modes. The resonance effect is
independent of the phase of the reconstructed bispectrum suggesting Fourier
mode extraction could be an efficient way to detect oscillatory bispectra in
the data.Comment: 17 pages, 12 figures. Matches published versio
Exploring nonlocal observables in shock wave collisions
We study the time evolution of 2-point functions and entanglement entropy in
strongly anisotropic, inhomogeneous and time-dependent N=4 super Yang-Mills
theory in the large N and large 't Hooft coupling limit using AdS/CFT. On the
gravity side this amounts to calculating the length of geodesics and area of
extremal surfaces in the dynamical background of two colliding gravitational
shockwaves, which we do numerically. We discriminate between three classes of
initial conditions corresponding to wide, intermediate and narrow shocks, and
show that they exhibit different phenomenology with respect to the nonlocal
observables that we determine. Our results permit to use (holographic)
entanglement entropy as an order parameter to distinguish between the two
phases of the cross-over from the transparency to the full-stopping scenario in
dynamical Yang-Mills plasma formation, which is frequently used as a toy model
for heavy ion collisions. The time evolution of entanglement entropy allows to
discern four regimes: highly efficient initial growth of entanglement, linear
growth, (post) collisional drama and late time (polynomial) fall off.
Surprisingly, we found that 2-point functions can be sensitive to the geometry
inside the black hole apparent horizon, while we did not find such cases for
the entanglement entropy.Comment: 28 pp, 9 figs; v2: updated references, changed color bars in Figure 2
and Figure
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