2,025 research outputs found

    Effect of detrending on multifractal characteristics

    Full text link
    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

    Get PDF
    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

    Full text link
    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--Δ\Delta splitting are calculated as well. The calculations have been done taking into account the quark sea polarization effects. The final results, including rotational 1/Nc1/N_c 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

    Full text link
    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

    Get PDF
    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

    Get PDF
    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

    Full text link
    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
    corecore