8,199 research outputs found
Digital simulation error curves for a spring-mass-damper system
Plotting digital simulation errors for a spring-mass-damper system and using these error curves to select type of integration, feedback update method, and number of samples per cycle at resonance reduces excessive number of samples per cycle and unnecessary iterations
Cosmic Microwave and Infrared Backgrounds cross-correlation for ISW detection
We investigate the cross-correlation between the cosmic infrared and
microwave backgrounds (CIB & CMB) anisotropies through the integrated
Sachs-Wolfe effect. We first describe the CIB anisotropies using a linearly
biased power spectrum, then derive the theoretical angular power spectrum of
the CMB-CIB cross-correlation for different instruments and frequencies. We
discuss the detectability of the ISW signal by performing a signal-to-noise
(SNR) analysis with our predicted spectra. The significances obtained range
from 6{\sigma} to 7{\sigma} in an ideal case, depending on the frequency ; in
realistic cases which account for the presence of noise including astrophysical
contaminants, the results span the range 2-5{\sigma}, depending strongly on the
major contribution to the noise term.Comment: 4 pages, 1 table. Contribution to the proceedings of the
International Conference on Gravitation and Cosmology, Goa, India, December,
201
The Age of the Universe and the Cosmological Constant Determined from Cosmic Microwave Background Anisotropy Measurements
If Omega_tot = 1 and structure formed from adiabatic initial conditions then
the age of the Universe, as constrained by measurements of the cosmic microwave
background (CMB), is t_0=14.0 +/- 0.5 Gyr. The uncertainty is surprisingly
small given that CMB data alone constrain neither h nor Omega_Lambda
significantly. It is due to the tight (and accidental) correlation, in these
models, of the age with the angle subtended by the sound horizon on the
last--scattering surface and thus with the well-determined acoustic peak
locations. If we assume either the HST Key Project result h = 0.72 \pm .08 or
simply that h > 0.55, we find Omega_Lambda > 0.4 at 95% confidence--another
argument for dark energy, independent of supernovae observations. Our analysis
is greatly simplified by the Monte Carlo Markov chain approach to Bayesian
inference combined with a fast method for calculating angular power spectra.Comment: 5 pages, including 2 figures and one table final published versio
CMB Power Spectrum Estimation via Hierarchical Decomposition
We have developed a fast, accurate and generally applicable method for
inferring the power spectrum and its uncertainties from maps of the cosmic
microwave background (CMB) in the presence of inhomogeneous and correlated
noise. For maps with 10 to 100 thousand pixels, we apply an exact power
spectrum estimation algorithm to submaps of the data at various resolutions,
and then combine the results in an optimal manner. To analyze larger maps
efficiently one must resort to sub-optimal combinations in which cross-map
power spectrum error correlations are only calculated approximately. We expect
such approximations to work well in general, and in particular for the
megapixel maps to come from the next generation of satellite missions.Comment: 10 pages, 5 figures, to be submitted to Phys. Rev.
Inhomogeneous reionization and the polarization of the cosmic microwave background
In a universe with inhomogeneous reionization, the ionized patches create a
second order signal in the cosmic microwave background polarization anisotropy.
This signal originates in the coupling of the free electron fluctuation to the
quadruple moment of the temperature anisotropy. We examine the contribution
from a simple inhomogeneous reionization model and find that the signal from
such a process is below the detectable limits of the Planck Surveyor mission.
However t he signal is above the fundamental uncertainty limit from cosmic
variance, so th at a future detection with a high accuracy experiment on
sub-arcminute scales is possible.Comment: 10 pages, 2 eps figures, final version accepted for publication in
ApJ Letter
Clients\u27 Internal Representations of Their Therapists
Thirteen adults in long-term individual psychotherapy were interviewed regarding their internal representations (defined as bringing to awareness the internalized image ) of their therapists. Results indicated that in the context of a good therapeutic relationship, clients\u27 internal representations combined auditory, visual, and kinesthetic (i.e., felt presence) modalities; were triggered when clients thought about past or future sessions, or when distressed; occurred in diverse locations; and varied in frequency, duration, and intensity. Clients felt positively about their representations and used them to introspect or influence therapy within sessions, beyond sessions, or both. The frequency of, comfort with, and use of clients\u27 internal representations increased over the course of therapy, and the representations benefited the therapy and therapeutic relationship. Therapists tended not to take a deliberate role in creating clients\u27 internal representations, and few clients discussed their internal representations with their therapists
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