2,025 research outputs found
Effect of detrending on multifractal characteristics
Different variants of MFDFA technique are applied in order to investigate
various (artificial and real-world) time series. Our analysis shows that the
calculated singularity spectra are very sensitive to the order of the
detrending polynomial used within the MFDFA method. The relation between the
width of the multifractal spectrum (as well as the Hurst exponent) and the
order of the polynomial used in calculation is evident. Furthermore, type of
this relation itself depends on the kind of analyzed signal. Therefore, such an
analysis can give us some extra information about the correlative structure of
the time series being studied.Comment: Presented by P. O\'swi\k{e}cimka at FENS2012 conference, 17 pages, 9
figure
On coupling consistant dependence of Gauge fields
Classical gauge fields (pure, coupled to the Dirac, scalar and gravitational fields) are investigated in the weak-coupling and strong-coupling limits. Several results concerning coupling constant dependence of fields in these regions are given. In particular, validity of the weak-coupling perturbative techniques is questioned for dynamical and non-singular solutions to the field equations
Electromagnetic form factors of the nucleon in the chiral quark soliton model
In this paper we present the derivation as well as the numerical results for
the electromagnetic form factors of the nucleon within the chiral quark soliton
model in the semiclassical quantization scheme. The model is based on
semibosonized SU(2) Nambu -- Jona-Lasinio lagrangean, where the boson fields
are treated as classical ones. Other observables, namely the nucleon mean
squared radii, the magnetic moments, and the nucleon-- splitting are
calculated as well. The calculations have been done taking into account the
quark sea polarization effects. The final results, including rotational
corrections, are compared with the existing experimental data, and they are
found to be in a good agreement for the constituent quark mass of about 420
MeV. The only exception is the neutron electric form factor which is
overestimated.Comment: 17 pages, 11 figures added as postscript files (uuencoded), RevTeX
format, no special macros, final version to appear in Nucl.Phys.A (1995
Dynamics of an Inelastic Gravitational Billiard with Rotation
The seminal physical model for investigating formulations of nonlinear
dynamics is the billiard. Gravitational billiards provide an experimentally
accessible arena for their investigation. We present a mathematical model that
captures the essential dynamics required for describing the motion of a
realistic billiard for arbitrary boundaries, where we include rotational
effects and additional forms of energy dissipation. Simulations of the model
are applied to parabolic, wedge and hyperbolic billiards that are driven
sinusoidally. The simulations demonstrate that the parabola has stable,
periodic motion, while the wedge and hyperbola (at high driving frequencies)
appear chaotic. The hyperbola, at low driving frequencies, behaves similarly to
the parabola; i.e., has regular motion. Direct comparisons are made between the
model's predictions and previously published experimental data. The value of
the coefficient of restitution employed in the model resulted in good agreement
with the experimental data for all boundary shapes investigated. It is shown
that the data can be successfully modeled with a simple set of parameters
without an assumption of exotic energy dependence.Comment: 11 pages, 11 figures. arXiv admin note: substantial text overlap with
arXiv:1103.443
High resolution CMB power spectrum from the complete ACBAR data set
In this paper, we present results from the complete set of cosmic microwave
background (CMB) radiation temperature anisotropy observations made with the
Arcminute Cosmology Bolometer Array Receiver (ACBAR) operating at 150 GHz. We
include new data from the final 2005 observing season, expanding the number of
detector-hours by 210% and the sky coverage by 490% over that used for the
previous ACBAR release. As a result, the band-power uncertainties have been
reduced by more than a factor of two on angular scales encompassing the third
to fifth acoustic peaks as well as the damping tail of the CMB power spectrum.
The calibration uncertainty has been reduced from 6% to 2.1% in temperature
through a direct comparison of the CMB anisotropy measured by ACBAR with that
of the dipole-calibrated WMAP5 experiment. The measured power spectrum is
consistent with a spatially flat, LambdaCDM cosmological model. We include the
effects of weak lensing in the power spectrum model computations and find that
this significantly improves the fits of the models to the combined ACBAR+WMAP5
power spectrum. The preferred strength of the lensing is consistent with
theoretical expectations. On fine angular scales, there is weak evidence (1.1
sigma) for excess power above the level expected from primary anisotropies. We
expect any excess power to be dominated by the combination of emission from
dusty protogalaxies and the Sunyaev-Zel'dovich effect (SZE). However, the
excess observed by ACBAR is significantly smaller than the excess power at ell
> 2000 reported by the CBI experiment operating at 30 GHz. Therefore, while it
is unlikely that the CBI excess has a primordial origin; the combined ACBAR and
CBI results are consistent with the source of the CBI excess being either the
SZE or radio source contamination.Comment: Submitted to ApJ; Changed to apply a WMAP5-based calibration. The
cosmological parameter estimation has been updated to include WMAP
A measurement of secondary cosmic microwave background anisotropies with two years of South Pole Telescope observations
We present the first three-frequency South Pole Telescope (SPT) cosmic
microwave background (CMB) power spectra. The band powers presented here cover
angular scales 2000 < ell < 9400 in frequency bands centered at 95, 150, and
220 GHz. At these frequencies and angular scales, a combination of the primary
CMB anisotropy, thermal and kinetic Sunyaev-Zel'dovich (SZ) effects, radio
galaxies, and cosmic infrared background (CIB) contributes to the signal. We
combine Planck and SPT data at 220 GHz to constrain the amplitude and shape of
the CIB power spectrum and find strong evidence for non-linear clustering. We
explore the SZ results using a variety of cosmological models for the CMB and
CIB anisotropies and find them to be robust with one exception: allowing for
spatial correlations between the thermal SZ effect and CIB significantly
degrades the SZ constraints. Neglecting this potential correlation, we find the
thermal SZ power at 150 GHz and ell = 3000 to be 3.65 +/- 0.69 muK^2, and set
an upper limit on the kinetic SZ power to be less than 2.8 muK^2 at 95%
confidence. When a correlation between the thermal SZ and CIB is allowed, we
constrain a linear combination of thermal and kinetic SZ power: D_{3000}^{tSZ}
+ 0.5 D_{3000}^{kSZ} = 4.60 +/- 0.63 muK^2, consistent with earlier
measurements. We use the measured thermal SZ power and an analytic, thermal SZ
model calibrated with simulations to determine sigma8 = 0.807 +/- 0.016.
Modeling uncertainties involving the astrophysics of the intracluster medium
rather than the statistical uncertainty in the measured band powers are the
dominant source of uncertainty on sigma8 . We also place an upper limit on the
kinetic SZ power produced by patchy reionization; a companion paper uses these
limits to constrain the reionization history of the Universe.Comment: 25 pages; 14 figures; Submitted to ApJ (Updated to reflect referee
comments
Measurements of Secondary Cosmic Microwave Background Anisotropies with the South Pole Telescope
We report cosmic microwave background (CMB) power spectrum measurements from
the first 100 sq. deg. field observed by the South Pole Telescope (SPT) at 150
and 220 GHz. On angular scales where the primary CMB anisotropy is dominant,
ell ~< 3000, the SPT power spectrum is consistent with the standard LambdaCDM
cosmology. On smaller scales, we see strong evidence for a point source
contribution, consistent with a population of dusty, star-forming galaxies.
After we mask bright point sources, anisotropy power on angular scales of 3000
50 at both frequencies. We
combine the 150 and 220 GHz data to remove the majority of the point source
power, and use the point source subtracted spectrum to detect
Sunyaev-Zel'dovich (SZ) power at 2.6 sigma. At ell=3000, the SZ power in the
subtracted bandpowers is 4.2 +/- 1.5 uK^2, which is significantly lower than
the power predicted by a fiducial model using WMAP5 cosmological parameters.
This discrepancy may suggest that contemporary galaxy cluster models
overestimate the thermal pressure of intracluster gas. Alternatively, this
result can be interpreted as evidence for lower values of sigma8. When combined
with an estimate of the kinetic SZ contribution, the measured SZ amplitude
shifts sigma8 from the primary CMB anisotropy derived constraint of 0.794 +/-
0.028 down to 0.773 +/- 0.025. The uncertainty in the constraint on sigma8 from
this analysis is dominated by uncertainties in the theoretical modeling
required to predict the amplitude of the SZ power spectrum for a given set of
cosmological parameters.Comment: 28 pages, 11 figures, submitted to Ap
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