812 research outputs found
Automated supervised classification of variable stars I. Methodology
The fast classification of new variable stars is an important step in making
them available for further research. Selection of science targets from large
databases is much more efficient if they have been classified first. Defining
the classes in terms of physical parameters is also important to get an
unbiased statistical view on the variability mechanisms and the borders of
instability strips. Our goal is twofold: provide an overview of the stellar
variability classes that are presently known, in terms of some relevant stellar
parameters; use the class descriptions obtained as the basis for an automated
`supervised classification' of large databases. Such automated classification
will compare and assign new objects to a set of pre-defined variability
training classes. For every variability class, a literature search was
performed to find as many well-known member stars as possible, or a
considerable subset if too many were present. Next, we searched on-line and
private databases for their light curves in the visible band and performed
period analysis and harmonic fitting. The derived light curve parameters are
used to describe the classes and define the training classifiers. We compared
the performance of different classifiers in terms of percentage of correct
identification, of confusion among classes and of computation time. We describe
how well the classes can be separated using the proposed set of parameters and
how future improvements can be made, based on new large databases such as the
light curves to be assembled by the CoRoT and Kepler space missions.Comment: This paper has been accepted for publication in Astronomy and
Astrophysics (reference AA/2007/7638) Number of pages: 27 Number of figures:
1
Highlights from the 16th International Society for Computational Biology Student Council Symposium 2020.
In this meeting overview, we summarise the scientific program and organisation of the 16th International Society for Computational Biology Student Council Symposium in 2020 (ISCB SCS2020). This symposium was the first virtual edition in an uninterrupted series of symposia that has been going on for 15 years, aiming to unite computational biology students and early career researchers across the globe. [Abstract copyright: Copyright: © 2021 Cuypers WL et al.
Large-volume metrology instrument selection and measurability analysis
A wide range of metrology processes are involved in the manufacture of large products. In addition to the traditional tool-setting and product-verification operations, increasingly flexible metrology-enabled automation is also being used. Faced with many possible measurement problems and a very large number of metrology instruments employing diverse technologies, the selection of the appropriate instrument for a given task can be highly complex. Also, as metrology has become a key manufacturing process, it should be considered in the early stages of design, and there is currently very little research to support this. This paper provides an overview of the important selection criteria for typical measurement processes and presents some novel selection strategies. Metrics that can be used to assess measurability are also discussed. A prototype instrument selection and measurability analysis application is also presented, with discussion of how this can be used as the basis for development of a more sophisticated measurement planning tool. © 2010 Authors
CP violation at a linear collider with transverse polarization
We show how transverse beam polarization at colliders can provide a
novel means to search for CP violation by observing the distribution of a
single final-state particle without measuring its spin. We suggest an azimuthal
asymmetry which singles out interference terms between standard model
contribution and new-physics scalar or tensor effective interactions in the
limit in which the electron mass is neglected. Such terms are inaccessible with
unpolarized or longitudinally polarized beams. The asymmetry is sensitive to CP
violation when the transverse polarizations of the electron and positron are in
opposite senses. The sensitivity of planned future linear colliders to
new-physics CP violation in is estimated in a
model-independent parametrization. It would be possible to put a bound of TeV on the new-physics scale at the 90% C.L. for
GeV and , with transverse polarizations of
80% and 60% for the electron and positron beams, respectively.Comment: 15 pages, latex, includes 5 figures. This version (v3) corresponds to
publication in Physical Review; extended version of v2 which corresponded to
LC note LC-TH-2003-099 with corrected figure caption
Measurement of the electric dipole moment using longitudinal polarization of beams
Certain CP-odd momentum correlations in the production and subsequent decay
of pairs in collisions are enhanced significantly when the
and beams are longitudinally polarized. These may be used to probe
the real and imaginary parts of , the electric dipole moment of
the . Closed-form expressions for these ``vector correlations'' and the
standard deviation of the operators defining them due to standard model
interactions are presented for the two-body final states of decays. If
42\% average polarization of each beam is achieved, as proposed for the
tau-charm factories, with equal integrated luminosities for each sign of
polarization and a total yield of pairs, it is
possible to attain sensitivities for of , , cm respectively and for of , , cm respectively at the three operating center-of-mass energies of
3.67, 4.25 and 10.58 GeV. These bounds emerge when the effects of a posible
weak dipole form factor are negligible as is the case when it is of
the same order of magnitude as . Furthermore, in such a
polarization experiment where different polarizations are possible, a
model-independent disentangling of their individual effects is possible, and a
technique to achieve this is described. A strong longitudinal polarization
physics programme at the tau-charm factory appears warranted.Comment: 30 pages, latex, no figure
Lepton flavor violating signals of a little Higgs model at the high energy linear colliders
Littlest Higgs model predicts the existence of the doubly charged
scalars , which generally have large flavor changing couplings
to leptons. We calculate the contributions of to the lepton
flavor violating processes and , and compare our numerical results with the current
experimental upper limits on these processes. We find that some of these
processes can give severe constraints on the coupling constant and the
mass parameter . Taking into account the constraints on these free
parameters, we further discuss the possible lepton flavor violating signals of
at the high energy linear collider
experiments. Our numerical results show that the possible signals of
might be detected via the subprocesses in the future experiments.Comment: 16 pages, 7 figures. Discussions and references added, typos
correcte
Quantization of eletric charge, the neutrino and generation nonuniversality
text of abstract It is showed that the eletric charge quantization is
unconnected to Majorana neutrino in the non-universal generations
leptoquark-bilepton flavordynamics which includes the right-handed neutrino and
an explicit U(1) factor in the gauge semisimple group.Comment: 4 pages, latex ps, no figure
Spectrum Analysis of Bright Kepler Gamma Doradus Candidate Stars
Ground-based spectroscopic follow-up observations of the pulsating stars
observed by the Kepler satellite mission are needed for their asteroseismic
modelling. We aim to derive the fundamental parameters for a sample of 26 Gamma
Doradus candidate stars observed by the Kepler satellite mission to accomplish
one of the required preconditions for their asteroseismic modelling and to
compare our results with the types of pulsators expected from the existing
light curve analysis. We use the spectrum synthesis method to derive the
fundamental parameters like Teff, logg, [M/H], and vsini from newly obtained
spectra and compute the spectral energy distribution from literature photometry
to get an independent measure of Teff. We find that most of the derived Teff
values agree with the values given in the Kepler Input Catalogue. According to
their positions in the HR-diagram three stars are expected Gamma Dor stars, ten
stars are expected Delta Sct stars, and seven stars are possibly Delta Sct
stars at the hot border of the instability strip. Four stars in our sample are
found to be spectroscopic binary candidates and four stars have very low
metallicity where two show about solar C abundance. Six of the 10 stars located
in the Delta Sct instability region of the HR-diagram show both Delta Sct and
Gamma Dor-type oscillations in their light curves implying that Gamma Dor-like
oscillations are much more common among the Delta Sct stars than predicted by
theory. Moreover, seven stars showing periods in the Delta Sct and the Delta
Sct-Gamma Dor range in their light curves are located in the HR-diagram left of
the blue edge of the theoretical Delta Sct instability strip. The consistency
of these findings with recent investigations based on high-quality Kepler data
implies the need for a revision of the theoretical Gamma Dor and Delta Sct
instability strips.Comment: 10 pages, 3 figures, 7 tables; accepted for publication in MNRA
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