1,952 research outputs found
Imprints of Nuclear Symmetry Energy on Properties of Neutron Stars
Significant progress has been made in recent years in constraining the
density dependence of nuclear symmetry energy using terrestrial nuclear
laboratory data. Around and below the nuclear matter saturation density, the
experimental constraints start to merge in a relatively narrow region. At
supra-saturation densities, there are, however, still large uncertainties.
After summarizing the latest experimental constraints on the density dependence
of nuclear symmetry energy, we highlight a few recent studies examining
imprints of nuclear symmetry energy on the binding energy, energy release
during hadron-quark phase transitions as well as the -mode frequency and
damping time of gravitational wave emission of neutron stars.Comment: 10 pages. Invited talk given in the Nuclear Astrophysics session of
INPC2010, July 4-9, 2010, Vancouver, Canada; Journal of Physics: Conference
Series (2011
Effect of extreme data loss on long-range correlated and anti-correlated signals quantified by detrended fluctuation analysis
We investigate how extreme loss of data affects the scaling behavior of
long-range power-law correlated and anti-correlated signals applying the DFA
method. We introduce a segmentation approach to generate surrogate signals by
randomly removing data segments from stationary signals with different types of
correlations. These surrogate signals are characterized by: (i) the DFA scaling
exponent of the original correlated signal, (ii) the percentage of
the data removed, (iii) the average length of the removed (or remaining)
data segments, and (iv) the functional form of the distribution of the length
of the removed (or remaining) data segments. We find that the {\it global}
scaling exponent of positively correlated signals remains practically unchanged
even for extreme data loss of up to 90%. In contrast, the global scaling of
anti-correlated signals changes to uncorrelated behavior even when a very small
fraction of the data is lost. These observations are confirmed on the examples
of human gait and commodity price fluctuations. We systematically study the
{\it local} scaling behavior of signals with missing data to reveal deviations
across scales. We find that for anti-correlated signals even 10% of data loss
leads to deviations in the local scaling at large scales from the original
anti-correlated towards uncorrelated behavior. In contrast, positively
correlated signals show no observable changes in the local scaling for up to
65% of data loss, while for larger percentage, the local scaling shows
overestimated regions (with higher local exponent) at small scales, followed by
underestimated regions (with lower local exponent) at large scales. Finally, we
investigate how the scaling is affected by the statistics of the remaining data
segments in comparison to the removed segments
Noise Effects on the Complex Patterns of Abnormal Heartbeats
Patients at high risk for sudden death often exhibit complex heart rhythms in
which abnormal heartbeats are interspersed with normal heartbeats. We analyze
such a complex rhythm in a single patient over a 12-hour period and show that
the rhythm can be described by a theoretical model consisting of two
interacting oscillators with stochastic elements. By varying the magnitude of
the noise, we show that for an intermediate level of noise, the model gives
best agreement with key statistical features of the dynamics.Comment: 4 pages, 4 figures, RevTe
Recommended from our members
Tissue multifractality and Born approximation in analysis of light scattering: a novel approach for precancers detection
Multifractal, a special class of complex self-affine processes, are under recent intensive investigations because of their fundamental nature and potential applications in diverse physical systems. Here, we report on a novel light scattering-based inverse method for extraction/quantification of multifractality in the spatial distribution of refractive index of biological tissues. The method is based on Fourier domain pre-processing via the Born approximation, followed by the Multifractal Detrended Fluctuation Analysis. The approach is experimentally validated in synthetic multifractal scattering phantoms, and tested on biopsy tissue slices. The derived multifractal properties appear sensitive in detecting cervical precancerous alterations through an increase of multifractality with pathology progression, demonstrating the potential of the developed methodology for novel precancer biomarker identification and tissue diagnostic tool. The novel ability to delineate the multifractal optical properties from light scattering signals may also prove useful for characterizing a wide variety of complex scattering media of non-biological origin
Boson stars in massive dilatonic gravity
We study equilibrium configurations of boson stars in the framework of a
class scalar-tensor theories of gravity with massive gravitational scalar
(dilaton). In particular we investigate the influence of the mass of the
dilaton on the boson star structure. We find that the masses of the boson stars
in presence of dilaton are close to those in general relativity and they are
sensitive to the ratio of the boson mass to the dilaton mass within a typical
few percent. It turns out also that the boson star structure is mainly
sensitive to the mass term of the dilaton potential rather to the exact form of
the potential.Comment: 9 pages, latex, 9 figures, one figure dropped, new comments added,
new references added, typos correcte
Askey-Wilson Type Functions, With Bound States
The two linearly independent solutions of the three-term recurrence relation
of the associated Askey-Wilson polynomials, found by Ismail and Rahman in [22],
are slightly modified so as to make it transparent that these functions satisfy
a beautiful symmetry property. It essentially means that the geometric and the
spectral parameters are interchangeable in these functions. We call the
resulting functions the Askey-Wilson functions. Then, we show that by adding
bound states (with arbitrary weights) at specific points outside of the
continuous spectrum of some instances of the Askey-Wilson difference operator,
we can generate functions that satisfy a doubly infinite three-term recursion
relation and are also eigenfunctions of -difference operators of arbitrary
orders. Our result provides a discrete analogue of the solutions of the purely
differential version of the bispectral problem that were discovered in the
pioneering work [8] of Duistermaat and Gr\"unbaum.Comment: 42 pages, Section 3 moved to the end, minor correction
Thermoacoustic tomography arising in brain imaging
We study the mathematical model of thermoacoustic and photoacoustic
tomography when the sound speed has a jump across a smooth surface. This models
the change of the sound speed in the skull when trying to image the human
brain. We derive an explicit inversion formula in the form of a convergent
Neumann series under the assumptions that all singularities from the support of
the source reach the boundary
Effective one-body approach to the relativistic two-body problem
The relativistic 2-body problem, much like the non-relativistic one, is
reduced to describing the motion of an effective particle in an external field.
The concept of a relativistic reduced mass and effective particle energy
introduced some 30 years ago to compute relativistic corrections to the Balmer
formula in quantum electrodynamics, is shown to work equally well for classical
electromagnetic and gravitational interaction. The results for the
gravitational 2-body problem have more than academic interest since they apply
to the study of binary pulsars that provide precision tests for general
relativity. They are compared with recent results derived by other methods.Comment: 9 pages, latex, no figures. Minor amendments, comments, new
references and acknowledgments adde
Common Scaling Patterns in Intertrade Times of U. S. Stocks
We analyze the sequence of time intervals between consecutive stock trades of
thirty companies representing eight sectors of the U. S. economy over a period
of four years. For all companies we find that: (i) the probability density
function of intertrade times may be fit by a Weibull distribution; (ii) when
appropriately rescaled the probability densities of all companies collapse onto
a single curve implying a universal functional form; (iii) the intertrade times
exhibit power-law correlated behavior within a trading day and a consistently
greater degree of correlation over larger time scales, in agreement with the
correlation behavior of the absolute price returns for the corresponding
company, and (iv) the magnitude series of intertrade time increments is
characterized by long-range power-law correlations suggesting the presence of
nonlinear features in the trading dynamics, while the sign series is
anti-correlated at small scales. Our results suggest that independent of
industry sector, market capitalization and average level of trading activity,
the series of intertrade times exhibit possibly universal scaling patterns,
which may relate to a common mechanism underlying the trading dynamics of
diverse companies. Further, our observation of long-range power-law
correlations and a parallel with the crossover in the scaling of absolute price
returns for each individual stock, support the hypothesis that the dynamics of
transaction times may play a role in the process of price formation.Comment: 8 pages, 5 figures. Presented at The Second Nikkei Econophysics
Workshop, Tokyo, 11-14 Nov. 2002. A subset appears in "The Application of
Econophysics: Proceedings of the Second Nikkei Econophysics Symposium",
editor H. Takayasu (Springer-Verlag, Tokyo, 2003) pp.51-57. Submitted to
Phys. Rev. E on 25 June 200
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