2,672 research outputs found
Natural entropy fluctuations discriminate similar looking electric signals emitted from systems of different dynamics
Complexity measures are introduced, that quantify the change of the natural
entropy fluctuations at different length scales in time-series emitted from
systems operating far from equilibrium. They identify impending sudden cardiac
death (SD) by analyzing fifteen minutes electrocardiograms, and comparing to
those of truly healthy humans (H). These measures seem to be complementary to
the ones suggested recently [Phys. Rev. E {\bf 70}, 011106 (2004)] and
altogether enable the classification of individuals into three categories: H,
heart disease patients and SD. All the SD individuals, who exhibit critical
dynamics, result in a common behavior.Comment: Published in Physical Review
Multifractality and scale invariance in human heartbeat dynamics
Human heart rate is known to display complex fluctuations. Evidence of
multifractality in heart rate fluctuations in healthy state has been reported
[Ivanov et al., Nature {\bf 399}, 461 (1999)]. This multifractal character
could be manifested as a dependence on scale or beat number of the probability
density functions (PDFs) of the heart rate increments. On the other hand, scale
invariance has been recently reported in a detrended analysis of healthy heart
rate increments [Kiyono et al., Phys. Rev. Lett. {\bf 93}, 178103 (2004)]. In
this paper, we resolve this paradox by clarifying that the scale invariance
reported is actually exhibited by the PDFs of the sum of detrended healthy
heartbeat intervals taken over different number of beats, and demonstrating
that the PDFs of detrended healthy heart rate increments are scale dependent.
Our work also establishes that this scale invariance is a general feature of
human heartbeat dynamics, which is shared by heart rate fluctuations in both
healthy and pathological states
On scattering cross sections and durations near an isolated compound-resonance, distorted by the non-resonant background, in the center-of-mass and laboratory systems
During last 20 years there was revealed and published the phenomenon of the
appearing of the time advance instead of the time delay at the region of a
compound-nucleus resonance, distorted by the non-resonant background (in the
center-of-mass (C-) system). This phenomenon is usually accompanied by a
minimum in the cross section near the same energy. Here we analyze the cross
section and the time delay of the nucleon-nucleus scattering in the laboratory
(L-) system. In the L-system the delay-advance phenomenon does not appear. We
use and concretize the non-standard analytical transformations of the cross
section from the C-system to the L-system, obtained in our previous papers.
They are illustrated by the calculations of energy dependences of cross
sections in the L-system for several cases of nucleon elastic scattering by
nuclei 12C, 16O, 28Si, 52Cr, 56Fe and 64Ni at the range of distorted resonances
in comparison with the experimental data.Comment: 11 pages, 7 figure
Entropy in the natural time-domain
A surrogate data analysis is presented, which is based on the fluctuations of
the ``entropy'' defined in the natural time-domain [Phys. Rev. E {\bf 68},
031106, 2003]. This entropy is not a static one as, for example, the Shannon
entropy. The analysis is applied to three types of time-series, i.e., seismic
electric signals, ``artificial'' noises and electrocardiograms, and
``recognizes'' the non-Markovianity in all these signals. Furthermore, it
differentiates the electrocardiograms of healthy humans from those of the
sudden cardiac death ones. If and denote the
standard deviation when calculating the entropy by means of a time-window
sweeping through the original data and the ``shuffled'' (randomized) data,
respectively, it seems that the ratio plays a
key-role. The physical meaning of is investigated.Comment: Published in Physical Review
Some Properties of Domain Wall Solution in the Randall-Sundrum Model
Properties of the domain wall (kink) solution in the 5 dimensional
Randall-Sundrum model are examined both {\it analytically} and {\it
numerically}. The configuration is derived by the bulk Higgs mechanism. We
focus on 1) the convergence property of the solution, 2) the stableness of the
solution, 3) the non-singular property of the Riemann curvature, 4) the
behaviours of the warp factor and the Higgs field. It is found that the bulk
curvature changes the sign around the surface of the wall. We also present some
{\it exact} solutions for two simple cases: a) the no potential case, b) the
cosmological term dominated case. Both solutions have the (naked) curvature
singularity. We can regard the domain wall solution as a singularity resolution
of the exact solutions.Comment: Typographical error correction for publication. 16 pages, 4 figure
Effective Field Theory and Unification in AdS Backgrounds
This work is an extension of our previous work, hep-th/0204160, which showed
how to systematically calculate the high energy evolution of gauge couplings in
compact AdS_5 backgrounds. We first directly compute the one-loop effects of
massive charged scalar fields on the low energy couplings of a gauge theory
propagating in the AdS background. It is found that scalar bulk mass scales
(which generically are of order the Planck scale) enter only logarithmically in
the corrections to the tree-level gauge couplings. As we pointed out
previously, we show that the large logarithms that appear in the AdS one-loop
calculation can be obtained within the confines of an effective field theory,
by running the Planck brane correlator from a high UV matching scale down to
the TeV scale. This result exactly reproduces our previous calculation, which
was based on AdS/CFT duality. We also calculate the effects of scalar fields
satisfying non-trivial boundary conditions (relevant for orbifold breaking of
bulk symmetries) on the running of gauge couplings.Comment: LaTeX, 27 pages; minor typos fixed, comments adde
Renormalization of One-Pion Exchange and Power Counting
The renormalization of the chiral nuclear interactions is studied. In leading
order, the cutoff dependence is related to the singular tensor interaction of
the one-pion exchange potential. In S waves and in higher partial waves where
the tensor force is repulsive this cutoff dependence can be absorbed by
counterterms expected at that order. In the other partial waves additional
contact interactions are necessary. The implications of this finding for the
effective-field-theory program in nuclear physics are discussed.Comment: 19 pages, 18 figure
Stress-energy tensor for a quantised bulk scalar field in the Randall-Sundrum brane model
We calculate the vacuum expectation value of the stress-energy tensor for a
quantised bulk scalar field in the Randall-Sundrum model, and discuss the
consequences of its local behaviour for the self-consistency of the model. We
find that, in general, the stress-energy tensor diverges in the vicinity of the
branes. Our main conclusion is that the stress-energy tensor is sufficiently
complicated that it has implications for the effective potential, or radion
stabilisation, methods that have so far been used.Comment: 16 pages, 3 figures. Minor changes made and references added. To
appear in Phys. Rev.
Casimir effect in de Sitter and Anti-de Sitter braneworlds
We discuss the bulk Casimir effect (effective potential) for a conformal or
massive scalar when the bulk represents five-dimensional AdS or dS space with
two or one four-dimensional dS brane, which may correspond to our universe.
Using zeta-regularization, the interesting conclusion is reached, that for both
bulks in the one-brane limit the effective potential corresponding to the
massive or to the conformal scalar is zero. The radion potential in the
presence of quantum corrections is found. It is demonstrated that both the dS
and the AdS braneworlds may be stabilized by using the Casimir force only. A
brief study indicates that bulk quantum effects are relevant for brane
cosmology, because they do deform the de Sitter brane. They may also provide a
natural mechanism yielding a decrease of the four-dimensional cosmological
constant on the physical brane of the two-brane configuration.Comment: 37 pages, LaTeX, references added, some revision is done, version to
appear in PR
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