1,490 research outputs found
A new Taxonomy of Continuous Global Optimization Algorithms
Surrogate-based optimization, nature-inspired metaheuristics, and hybrid
combinations have become state of the art in algorithm design for solving
real-world optimization problems. Still, it is difficult for practitioners to
get an overview that explains their advantages in comparison to a large number
of available methods in the scope of optimization. Available taxonomies lack
the embedding of current approaches in the larger context of this broad field.
This article presents a taxonomy of the field, which explores and matches
algorithm strategies by extracting similarities and differences in their search
strategies. A particular focus lies on algorithms using surrogates,
nature-inspired designs, and those created by design optimization. The
extracted features of components or operators allow us to create a set of
classification indicators to distinguish between a small number of classes. The
features allow a deeper understanding of components of the search strategies
and further indicate the close connections between the different algorithm
designs. We present intuitive analogies to explain the basic principles of the
search algorithms, particularly useful for novices in this research field.
Furthermore, this taxonomy allows recommendations for the applicability of the
corresponding algorithms.Comment: 35 pages total, 28 written pages, 4 figures, 2019 Reworked Versio
MOBSTER – III. HD 62658: a magnetic Bp star in an eclipsing binary with a non-magnetic ‘identical twin’
HD 62658 (B9p V) is a little-studied chemically peculiar star. Light curves obtained by the Kilodegree Extremely Little Telescope (KELT) and Transiting Exoplanet Survey Satellite (TESS) show clear eclipses with a period of about 4.75 d, as well as out-of-eclipse brightness modulation with the same 4.75 d period, consistent with synchronized rotational modulation of surface chemical spots. High-resolution ESPaDOnS circular spectropolarimetry shows a clear Zeeman signature in the line profile of the primary; there is no indication of a magnetic field in the secondary. PHOEBE modelling of the light curve and radial velocities indicates that the two components have almost identical masses of about 3 M_⊙. The primary’s longitudinal magnetic field〈B_z〉 varies between about +100 and −250 G, suggesting a surface magnetic dipole strength B_d = 850 G. Bayesian analysis of the Stokes V profiles indicates B_d = 650 G for the primary and B_d < 110 G for the secondary. The primary’s line profiles are highly variable, consistent with the hypothesis that the out-of-eclipse brightness modulation is a consequence of rotational modulation of that star’s chemical spots. We also detect a residual signal in the light curve after removal of the orbital and rotational modulations, which might be pulsational in origin; this could be consistent with the weak line profile variability of the secondary. This system represents an excellent opportunity to examine the consequences of magnetic fields for stellar structure via comparison of two stars that are essentially identical with the exception that one is magnetic. The existence of such a system furthermore suggests that purely environmental explanations for the origin of fossil magnetic fields are incomplete
An Efficient Algorithm for Optimizing Adaptive Quantum Metrology Processes
Quantum-enhanced metrology infers an unknown quantity with accuracy beyond
the standard quantum limit (SQL). Feedback-based metrological techniques are
promising for beating the SQL but devising the feedback procedures is difficult
and inefficient. Here we introduce an efficient self-learning
swarm-intelligence algorithm for devising feedback-based quantum metrological
procedures. Our algorithm can be trained with simulated or real-world trials
and accommodates experimental imperfections, losses, and decoherence
On stability of the neutron rich Oxygen isotopes
Stability with respect to neutron emission is studied for highly
neutron-excessive Oxygen isotopes in the framework of Hartree-Fock-Bogoliubov
approach with Skyrme forces Sly4 and Ska. Our calculations show increase of
stability around 40O.Comment: 5 pages, 3 figure
Closedness type regularity conditions for surjectivity results involving the sum of two maximal monotone operators
In this note we provide regularity conditions of closedness type which
guarantee some surjectivity results concerning the sum of two maximal monotone
operators by using representative functions. The first regularity condition we
give guarantees the surjectivity of the monotone operator , where and and are maximal monotone operators on
the reflexive Banach space . Then, this is used to obtain sufficient
conditions for the surjectivity of and for the situation when belongs
to the range of . Several special cases are discussed, some of them
delivering interesting byproducts.Comment: 11 pages, no figure
Size of the Vela Pulsar's Emission Region at 13 cm Wavelength
We present measurements of the size of the Vela pulsar in 3 gates across the
pulse, from observations of the distribution of intensity. We calculate the
effects on this distribution of noise in the observing system, and measure and
remove it using observations of a strong continuum source. We also calculate
and remove the expected effects of averaging in time and frequency. We find
that effects of variations in pulsar flux density and instrumental gain,
self-noise, and one-bit digitization are undetectably small. Effects of
normalization of the correlation are detectable, but do not affect the fitted
size. The size of the pulsar declines from 440 +/- 90 km (FWHM of best-fitting
Gaussian distribution) to less than 200 km across the pulse. We discuss
implications of this size for theories of pulsar emission.Comment: 51 pages, 10 figures. To appear in ApJ. Also available at
http://www.physics.ucsb.edu/~cgwinn/pulsar/size_14.p
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