14,722 research outputs found
DIAMONDS: a new Bayesian Nested Sampling tool. Application to Peak Bagging of solar-like oscillations
To exploit the full potential of Kepler light curves, sophisticated and
robust analysis tools are now required more than ever. Characterizing single
stars with an unprecedented level of accuracy and subsequently analyzing
stellar populations in detail are fundamental to further constrain stellar
structure and evolutionary models. We developed a new code, termed Diamonds,
for Bayesian parameter estimation and model comparison by means of the nested
sampling Monte Carlo (NSMC) algorithm, an efficient and powerful method very
suitable for high-dimensional and multi-modal problems. A detailed description
of the features implemented in the code is given with a focus on the novelties
and differences with respect to other existing methods based on NSMC. Diamonds
is then tested on the bright F8 V star KIC~9139163, a challenging target for
peak-bagging analysis due to its large number of oscillation peaks observed,
which are coupled to the blending that occurs between peaks, and the
strong stellar background signal. We further strain the performance of the
approach by adopting a 1147.5 days-long Kepler light curve. The Diamonds code
is able to provide robust results for the peak-bagging analysis of KIC~9139163.
We test the detection of different astrophysical backgrounds in the star and
provide a criterion based on the Bayesian evidence for assessing the peak
significance of the detected oscillations in detail. We present results for 59
individual oscillation frequencies, amplitudes and linewidths and provide a
detailed comparison to the existing values in the literature. Lastly, we
successfully demonstrate an innovative approach to peak bagging that exploits
the capability of Diamonds to sample multi-modal distributions, which is of
great potential for possible future automatization of the analysis technique.Comment: 22 pages, 14 figures, 3 tables. Accepted for publication in A&
Peak Bagging of red giant stars observed by Kepler: first results with a new method based on Bayesian nested sampling
The peak bagging analysis, namely the fitting and identification of single
oscillation modes in stars' power spectra, coupled to the very high-quality
light curves of red giant stars observed by Kepler, can play a crucial role for
studying stellar oscillations of different flavor with an unprecedented level
of detail. A thorough study of stellar oscillations would thus allow for deeper
testing of stellar structure models and new insights in stellar evolution
theory. However, peak bagging inferences are in general very challenging
problems due to the large number of observed oscillation modes, hence of free
parameters that can be involved in the fitting models. Effciency and robustness
in performing the analysis is what may be needed to proceed further. For this
purpose, we developed a new code implementing the Nested Sampling Monte Carlo
(NSMC) algorithm, a powerful statistical method well suited for Bayesian
analyses of complex problems. In this talk we show the peak bagging of a sample
of high signal-to-noise red giant stars by exploiting recent Kepler datasets
and a new criterion for the detection of an oscillation mode based on the
computation of the Bayesian evidence. Preliminary results for frequencies and
lifetimes for single oscillation modes, together with acoustic glitches, are
therefore presented.Comment: Conference Proceeding - CoRoT3-KASC7 The Space Photometry Revolution,
Toulouse, France, July 6-11 2014, 4 pages, 3 figure
Nonlocality, No-Signalling and Bell's Theorem investigated by Weyl's Conformal Differential Geometry
The principles and methods of the Conformal Quantum Geometrodynamics (CQG)
based on the Weyl's differential geometry are presented. The theory applied to
the case of the relativistic single quantum spin 1/2 leads a novel and
unconventional derivation of Dirac's equation. The further extension of the
theory to the case of two spins 1/2 in EPR entangled state and to the related
violation of Bell's inequalities leads, by an exact albeit non relativistic
analysis, to an insightful resolution of all paradoxes implied by quantum
nonlocality.Comment: arXiv admin note: text overlap with arXiv:1203.003
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