489 research outputs found
Classification of Fermi-LAT unidentified gamma-ray sources using CatBoost gradient boosting decision trees
The latest -LAT gamma-ray catalog, 4FGL-DR3, presents a large
fraction of sources without clear association to known counterparts, i.e.,
unidentified sources (unIDs). In this paper, we aim to classify them using
machine learning algorithms, which are trained with the spectral
characteristics of associated sources to predict the class of the unID
population. With the state-of-the-art algorithm, based on
gradient boosting decision trees, we are able to reach a 67% accuracy on a
23-class dataset. Removing a single of these classes -- blazars of uncertain
type -- increases the accuracy to 81%. If interested only in a binary
AGN/pulsar distinction, the model accuracy is boosted up to 99%. Additionally,
we perform an unsupervised search among both known and unID population, and try
to predict the number of clusters of similar sources, without prior knowledge
of their classes. The full code used to perform all calculations is provided as
an interactive Python notebook.Comment: 8 pages, 8 figures. Matches the accepted MNRAS versio
Redshift prediction of Fermi-LAT gamma-ray sources using CatBoost gradient boosting decision trees
The determination of distance is fundamental in astrophysics. Gamma-ray
sources are poorly characterized in this sense, as the limited angular
resolution and poor photon-count statistics in gamma-ray astronomy makes it
difficult to associate them to a multiwavelength object with known redshift.
Taking the 1794 active galactic nuclei (AGNs) with known redshift from the
Fermi-LAT latest AGN catalog, 4LAC-DR3, we employ machine learning techniques
to predict the distance of the rest of AGNs based on their spectral and spatial
properties. The state-of-the-art CatBoost algorithm reaches an average 0.56 R2
score with 0.46 root-mean-squared error (RMSE), predicting an average redshift
value of , with a maximum . We use the SHAP
explainer package to gain insights into the variables influence on the outcome,
and also study the extragalactic bakground light (EBL) implications. In a
second part, we use this regression model to predict the redshift of the
unassociated sample of the latest LAT point-source catalog, 4FGL-DR3, using the
results of a previous paper to determine the possible AGNs within them.Comment: 7 pages, 7 figures. Matches the accepted MNRAS versio
Multimarket Contact in Pharmaceutical Markets
The purpose of this paper is to analyze the effect of multimarket contact on the behavior of pharmaceutical firms controlling for different levels of regulatory constraints using IMS MIDAS database. Theoretically, firms that meet in several markets are expected to be capable of sustaining implicitly more profitable out- comes, even if perfect monitoring is not possible. Firms may find it profitable to redistribute their market power among markets where they are operating. We present evidence for nine OECD countries with different degrees of regulation and show that regulation affects the importance of economic forces on firms' price setting behavior. Furthermore, our results confirms the presence of the predictions of the multimarket theory for more market friendly countries (U.S. and Canada) and less regulated ones (U.K., Germany, Netherlands), in contrast, for highly regulated countries (Japan, France, Italy and Spain) the results are less clear with some countries beingPharmaceutical prices, Multimarket Contact, Regulation
Multimarket contact in pharmaceutical markets
We analyze the effect of multimarket contact on the pricing behavior of pharmaceutical firms controlling for different levels of regulatory constraints using the IMS MIDAS database for the industry. Theoretically, under product differentiation, firms may find it profitable to allocate their market power among markets where they are operating, specifically from more collusive to more competitive ones. We present evidence for nine OECD countries suggesting the existence of a multimarket effect for more market friendly countries (U.S. and Canada) and less regulated ones (U.K., Germany, Netherlands), while the results are more unstable for highly regulated countries with some countries being consistent with the theory (France) while others contradicting it (Japan, Italy and Spain). A key result indicates that in the latter countries, price constraints are so intense, that there is little room for allocating market power. Thus equilibrium prices are expected in general to be lower in regulated countries.Pharmaceutical prices, Multimarket Contact, Regulation
Acerca de una defectuosa educación matemática
El objetivo de este artÃculo es analizar algunos de los defectos más habituales que, a nuestro juicio, se producen en la enseñanza de las matemáticas, a la ver que hacer una reflexión sobre el grado de formación matemática de la sociedad española
Matemáticos españoles en los umbrales del siglo XX: La historia de nuestro despertar matemático
El papel que la matemática española ha jugado en el panorama internacional ha sido
siempre exiguo, salvo en la etapa de la dominación árabe (probablemente fuéramos entonces el foco cientÃfico más importante del mundo) y en estas últimas décadas
(actualmente se encuentra en torno al décimo puesto en la producción matemática mundial). En particular, a finales del siglo XVIII nuestro estado matemático es lamentable, pero a lo largo del XIX la situación va progresando. Esta mejora se percibe especialmente en su último tercio y, más aún, a raÃz de la crisis del 98 y durante las primeras décadas del siglo XX.
En las páginas siguientes estudiaremos quiénes fueron los matemáticos españoles más
importantes de finales del XIX y principios del XX, y cómo fue esa evolución a la que nos hemos referido. Pero para ello debemos comenzar un poco ante
Students\u27 perception of performance through self-assessment
This study was designed as a qualitative investigation and it focuses on the non-graded self-assessment adult ESL students make of their performance. It is based upon findings from previous studies of self-assessment in several settings (Glazer, 1999; Glazer et al., 1995; Optiz, 1995; Manning, 1997; Levy, 1999; Fazey, 1993; Boud, 1992; Orsmond et al., 1997; Sullivan and Hall, 1997; and Lan, 1996). The present research reports and analyzes data collected from eleven students who expressed their views concerning their performance through a checklist, two questionnaires and an interview in an ESL setting. The data collected and analyzed suggest that students are very capable of carrying out self-assessment; they are usually more demanding of themselves than their teachers are; and the process of self-assessment may help them realize ways to improve their performance
X-ray and gamma-ray limits on the primordial black hole abundance from Hawking radiation
The non-observation of Hawking radiation from primordial black holes of
g sets a conservative strong bound on their cosmological abundance. We
revisit this bound and show how it can be improved (both in mass reach and
strength) by an adequate modeling of the combined AGN and blazar emission in
the MeV range. We also estimate the sensitivity to the primordial black hole
abundance of a future X-ray experiment capable of identifying a significantly
larger number of astrophysical sources contributing to the diffuse background
in this energy range.Comment: 5 pages, 2 figures. Accepted for publication in Physics Letters
Constraints to dark matter annihilation from high-latitude hawc unidentified sources
The ΛCDM cosmological framework predicts the existence of thousands of subhalos in
our own Galaxy not massive enough to retain baryons and become visible. Yet, some of them may
outshine in gamma rays provided that the dark matter is made of weakly interacting massive particles
(WIMPs), which would self-annihilate and would appear as unidentified gamma-ray sources (unIDs)
in gamma-ray catalogs. Indeed, unIDs have proven to be competitive targets for dark matter searches
with gamma rays. In this work, we focus on the three high-latitude (|b| ≥ 10) sources present
in the 2HWC catalog of the High Altitude Water Cherenkov (HAWC) observatory with no clear
associations at other wavelengths. Indeed, only one of these sources, 2HWC J1040+308, is found to
be above the HAWC detection threshold when considering 760 days of data, i.e., a factor 1.5 more
exposure time than in the original 2HWC catalog. Other gamma-ray instruments, such as Fermi-LAT
or VERITAS at lower energies, do not detect the source. Also, this unID is reported as spatially
extended, making it even more interesting in a dark matter search context. While waiting for more
data that may shed further light on the nature of this source, we set competitive upper limits on the
annihilation cross section by comparing this HAWC unID to expectations based on state-of-the-art
N-body cosmological simulations of the Galactic subhalo population. We find these constraints to be
particularly competitive for heavy WIMPs, i.e., masses above ∼25 (40) TeV in the case of the b
¯b (τ
+Ï„
−)
annihilation channel, reaching velocity-averaged cross section values of 2 × 10−25 (5 × 10−25) cm3
·s
−1
.
Although far from testing the thermal relic cross section value, the obtained limits are independent
and nicely complementary to those from radically different DM analyses and targets, demonstrating
once again the high potential of this DM search approachJ.C.-B. and M.A.S.-C. are supported by the Atracción de Talento contract no. 2016-T1/TIC-1542
granted by the Comunidad de Madrid in Spain, by the Spanish Agencia Estatal de Investigación through
the grants PGC2018-095161-B-I00, IFT Centro de Excelencia Severo Ochoa SEV-2016-0597, and Red Consolider MultiDark FPA2017-90566-RED
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