17,249 research outputs found
A hierarchical Bayesian model to infer PL(Z) relations using Gaia parallaxes
Aims. We aim at creating a Bayesian model to infer the coefficients of PL or
PLZ relations that propagates uncertainties in the observables in a rigorous
and well founded way. Methods. We propose a directed acyclic graph to encode
the conditional probabilities of the inference model that will allow us to
infer probability distributions for the PL and PL(Z) relations. We evaluate the
model with several semi-synthetic data sets and apply it to a sample of 200
fundamental mode and first overtone mode RR Lyrae stars for which Gaia DR1
parallaxes and literature Ks-band mean magnitudes are available. We define and
test several hyperprior probabilities to verify their adequacy and check the
sensitivity of the solution with respect to the prior choice. Results. The main
conclusion of this work is the absolute necessity of incorporating the existing
correlations between the observed variables (periods, metallicities and
parallaxes) in the form of model priors in order to avoid systematically biased
results, especially in the case of non-negligible uncertainties in the
parallaxes. The tests with the semi-synthetic data based on the data set used
in Gaia Collaboration et al. (2017) reveal the significant impact that the
existing correlations between parallax, metallicity and periods have on the
inferred parameters. The relation coefficients obtained here have been
superseded by those presented in Muraveva et al. (2018a), that incorporates the
findings of this work and the more recent Gaia DR2 measurements.Comment: 14 pages, 12 figures. Submitted to A&
Thanks, but no thanks: women's avoidance of help-seeking in the context of a dependency-related stereotype
The stereotype that women are dependent on men is a commonly verbalized, potentially damaging aspect of benevolent sexism. We investigated how women may use behavioral disconfirmation of the personal applicability of the stereotype to negotiate such sexism. In an experiment (N = 86), we manipulated female college students’ awareness that women may be stereotyped by men as dependent. We then placed participants in a situation where they needed help. Women made aware of the dependency stereotype (compared to controls who were not) were less willing to seek help. They also displayed a stronger negative correlation between help-seeking and post help-seeking affect - such that the more help they sought, the worse they felt. We discuss the relevance of these findings for research concerning women’s help-seeking and their management of sexist stereotyping in everyday interaction. We also consider the implications of our results for those working in domains such as healthcare, teaching and counseling, where interaction with individuals in need and requiring help is common
Error Threshold for Color Codes and Random 3-Body Ising Models
We study the error threshold of color codes, a class of topological quantum
codes that allow a direct implementation of quantum Clifford gates suitable for
entanglement distillation, teleportation and fault-tolerant quantum
computation. We map the error-correction process onto a statistical mechanical
random 3-body Ising model and study its phase diagram via Monte Carlo
simulations. The obtained error threshold of p_c = 0.109(2) is very close to
that of Kitaev's toric code, showing that enhanced computational capabilities
does not necessarily imply lower resistance to noise.Comment: 4 pages, 3 figures, 1 tabl
A Search for Planetary Nebulae With the SDSS: the outer regions of M31
We have developed a method to identify planetary nebula (PN) candidates in
imaging data of the Sloan Digital Sky Survey (SDSS). This method exploits the
SDSS' five-band sampling of emission lines in PN spectra, which results in a
color signature distinct from that of other sources. Selection criteria based
on this signature can be applied to nearby galaxies in which PNe appear as
point sources. We applied these criteria to the whole area of M31 as scanned by
the SDSS, selecting 167 PN candidates that are located in the outer regions of
M31. The spectra of 80 selected candidates were then observed with the 2.2m
telescope at Calar Alto Observatory. These observations and cross-checks with
literature data show that our method has a selection rate efficiency of about
90%, but the efficiency is different for the different groups of PNe
candidates.
In the outer regions of M31, PNe trace different well-known morphological
features like the Northern Spur, the NGC205 Loop, the G1 Clump, etc. In
general, the distribution of PNe in the outer region 8<R<20 kpc along the minor
axis shows the "extended disk" - a rotationally supported low surface
brightness structure with an exponential scale length of 3.21+/-0.14 kpc and a
total mass of ~10^10 M_{\sun}, which is equivalent to the mass of M33. We
report the discovery of three PN candidates with projected locations in the
center of Andromeda NE, a very low surface brightness giant stellar structure
in the outer halo of M31. Two of the PNe were spectroscopically confirmed as
genuine PNe. These two PNe are located at projected distances along the major
axis of ~48 Kpc and ~41 Kpc from the center of M31 and are the most distant PNe
in M31 found up to now.Comment: 58 pages, 17 figures, 2 tables, Accepted to Astronomical Journa
Dirac Cat States in Relativistic Landau Levels
We show that a relativistic version of Schrodinger cat states, here called
Dirac cat states, can be built in relativistic Landau levels when an external
magnetic field couples to a relativistic spin 1/2 charged particle. Under
suitable initial conditions, the associated Dirac equation produces unitarily
Dirac cat states involving the orbital quanta of the particle in a well defined
mesoscopic regime. We demonstrate that the proposed Dirac cat states have a
purely relativistic origin and cease to exist in the non-relativistic limit. In
this manner, we expect to open relativistic quantum mechanics to the rich
structures of quantum optics and quantum information.Comment: Revtex4, color figures, submitted for publicatio
Scherk-Schwarz SUSY breaking from the viewpoint of 5D conformal supergravity
We reinterpret the Scherk-Schwarz (SS) boundary condition for SU(2)_R in a
compactified five-dimensional (5D) Poincare supergravity in terms of the
twisted SU(2)_U gauge fixing in 5D conformal supergravity. In such translation,
only the compensator hypermultiplet is relevant to the SS twist, and various
properties of the SS mechanism can be easily understood. Especially, we show
the correspondence between the SS twist and constant superpotentials within our
framework.Comment: 16 pages, no figur
Expert-Augmented Machine Learning
Machine Learning is proving invaluable across disciplines. However, its
success is often limited by the quality and quantity of available data, while
its adoption by the level of trust that models afford users. Human vs. machine
performance is commonly compared empirically to decide whether a certain task
should be performed by a computer or an expert. In reality, the optimal
learning strategy may involve combining the complementary strengths of man and
machine. Here we present Expert-Augmented Machine Learning (EAML), an automated
method that guides the extraction of expert knowledge and its integration into
machine-learned models. We use a large dataset of intensive care patient data
to predict mortality and show that we can extract expert knowledge using an
online platform, help reveal hidden confounders, improve generalizability on a
different population and learn using less data. EAML presents a novel framework
for high performance and dependable machine learning in critical applications
Propiedades mecánicas de películas híbridas (orgánico-inorgánico) sobre acero inoxidable 304
Este trabajo muestra la conformación de películas cerámicas del sistema híbridoSiO2 - TiO2-Polímero Orgánico, a partir de tetraetil-ortosilicato (Si (OC2H5)4), ytetra-butoxido de titanio (Ti(OBu)4) y sintetizado por el método sol-gel en diferentesconcentraciones volumétricas de los precursores. Este sistema híbrido se depositósobre sustratos de acero inoxidable AISI 304 mediante la técnica de inmersión (dipcoating).Se estudió la viabilidad de obtener recubrimientos híbridos homogéneossobre este tipo de sustrato y evaluar las propiedades superficiales. Para tal efecto, seestudió microdureza y adhesión del recubrimiento. Adicionalmente, se caracterizó lasuperficie de las películas por microscopía electrónica de barrido (MEB). Del estudiose concluye que las características de las películas cambian en función de la cantidadvolumétrica de los precursores utilizados en la conformación de las mismas
On the nature of the near-UV extended light in Seyfert galaxies
We study the nature of the extended near-UV emission in the inner kiloparsec
of a sample of 15 Seyfert galaxies which have both near-UV (F330W) and narrow
band [OIII] high resolution Hubble images. For the majority of the objects we
find a very similar morphology in both bands. From the [OIII] images we
construct synthetic images of the nebular continuum plus the emission line
contribution expected through the F330W filter, which can be subtracted from
the F330W images. We find that the emission of the ionised gas dominates the
near-UV extended emission in half of the objects. A further broad band
photometric study, in the bands F330W (U), F547M (V) and F160W (H), shows that
the remaining emission is dominated by the underlying galactic bulge
contribution. We also find a blue component whose nature is not clear in 4 out
of 15 objects. This component may be attributed to scattered light from the
AGN, to a young stellar population in unresolved star clusters, or to
early-disrupted clusters. Star forming regions and/or bright off-nuclear star
clusters are observed in 4/15 galaxies of the sample.Comment: 23 pages, 6 figures, 3 tables; accepted for publication in MNRA
Equianalytic and equisingular families of curves on surfaces
We consider flat families of reduced curves on a smooth surface S such that
each member C has the same number of singularities of fixed singularity types
and the corresponding (locally closed) subscheme H of the Hilbert scheme of S.
We are mainly concerned with analytic resp. topological singularity types and
give a sufficient condition for the smoothness of H (at C). Our results for
S=P^2 seem to be quite sharp for families of cuves of small degree d.Comment: LaTeX v 2.0
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