464 research outputs found
Use of Machine Learning for gamma/hadron separation with HAWC
Background showers triggered by hadrons represent over 99.9% of all particles
arriving at ground-based gamma-ray observatories. An important stage in the
data analysis of these observatories, therefore, is the removal of
hadron-triggered showers. Currently, the High-Altitude Water Cherenkov (HAWC)
gamma-ray observatory employs an algorithm based on a single cut in two
variables, unlike other ground-based gamma-ray observatories (e.g. H.E.S.S.,
VERITAS), which employ a large number of variables to separate the primary
particles. In this work, we explore machine learning techniques (Boosted
Decision Trees and Neural Networks) to identify the primary particles detected
by HAWC. Our new gamma/hadron separation techniques were tested on data from
the Crab nebula, the standard reference in Very High Energy astronomy, showing
an improvement compared to the standard HAWC background rejection method.Comment: Presented at the 37th International Cosmic Ray Conference (ICRC2021),
Berlin, Germany - Onlin
Bioprinting as a food production technique: Conceptual and ethical aspects, advantages and disadvantages, and applications
3D bioprinters present techniques that have various applications in the food industry. For this reason, this work aims to compile and review various research works focused on the utilities and advantages of this type of machinery. Where we first mention the basis of these bioprinting techniques and then proceed to highlight the bioethical issues that surround their application in the food industry, analyze the current advantages and disadvantages, the user that has been given in the production of food for astronauts, and also mention some of the research that has been taking place in Latin America and the world. The greatest advantage of 3D bioprinting of food is the speed of production compared to traditional manufacturing methods, allowing one to obtain food with various geometric shapes; it allows control of the nutritional value, and the texture of the product, reduces environmental pollution and has the advantage of being able to take advantage of the greater performance of the materials required for production. Additionally, this technology is considered an alternative production technique that will be used to solve the problem of feeding in places of scarce resources such as space and areas not suitable for animal husbandry
Uniform Approximation from Symbol Calculus on a Spherical Phase Space
We use symbol correspondence and quantum normal form theory to develop a more
general method for finding uniform asymptotic approximations. We then apply
this method to derive a result we announced in an earlier paper, namely, the
uniform approximation of the -symbol in terms of the rotation matrices. The
derivation is based on the Stratonovich-Weyl symbol correspondence between
matrix operators and functions on a spherical phase space. The resulting
approximation depends on a canonical, or area preserving, map between two pairs
of intersecting level sets on the spherical phase space.Comment: 18 pages, 5 figure
Radio Detection of the Fermi LAT Blind Search Millisecond Pulsar J1311-3430
We report the detection of radio emission from PSR J1311-3430, the first
millisecond pulsar discovered in a blind search of Fermi Large Area Telescope
(LAT) gamma-ray data. We detected radio pulsations at 2 GHz, visible for <10%
of ~4.5-hrs of observations using the Green Bank Telescope (GBT). Observations
at 5 GHz with the GBT and at several lower frequencies with Parkes, Nancay, and
the Giant Metrewave Radio Telescope resulted in non-detections. We also report
the faint detection of a steep spectrum continuum radio source (0.1 mJy at 5
GHz) in interferometric imaging observations with the Jansky Very Large Array.
These detections demonstrate that PSR J1311-3430, is not radio quiet and
provides additional evidence that the radio beaming fraction of millisecond
pulsars is very large. The radio detection yields a distance estimate of 1.4
kpc for the system, yielding a gamma-ray efficiency of 30%, typical of
LAT-detected MSPs. We see apparent excess delay in the radio pulsar as the
pulsar appears from eclipse and we speculate on possible mechanisms for the
non-detections of the pulse at other orbital phases and observing frequencies.Comment: 6 pages, 4 figures. ApJ Letters, in pres
Moyal star product approach to the Bohr-Sommerfeld approximation
The Bohr-Sommerfeld approximation to the eigenvalues of a one-dimensional
quantum Hamiltonian is derived through order (i.e., including the
first correction term beyond the usual result) by means of the Moyal star
product. The Hamiltonian need only have a Weyl transform (or symbol) that is a
power series in , starting with , with a generic fixed point in
phase space. The Hamiltonian is not restricted to the kinetic-plus-potential
form. The method involves transforming the Hamiltonian to a normal form, in
which it becomes a function of the harmonic oscillator Hamiltonian.
Diagrammatic and other techniques with potential applications to other normal
form problems are presented for manipulating higher order terms in the Moyal
series.Comment: 27 pages, no figure
Discovery of Localized Regions of Excess 10-TeV Cosmic Rays
An analysis of 7 years of Milagro data performed on a 10-degree angular scale
has found two localized regions of excess of unknown origin with greater than
12 sigma significance. Both regions are inconsistent with gamma-ray emission
with high confidence. One of the regions has a different energy spectrum than
the isotropic cosmic-ray flux at a level of 4.6 sigma, and it is consistent
with hard spectrum protons with an exponential cutoff, with the most
significant excess at ~10 TeV. Potential causes of these excesses are explored,
but no compelling explanations are found.Comment: Submitted to PhysRevLet
Semiclassical analysis of Wigner -symbol
We analyze the asymptotics of the Wigner -symbol as a matrix element
connecting eigenfunctions of a pair of integrable systems, obtained by lifting
the problem of the addition of angular momenta into the space of Schwinger's
oscillators. A novel element is the appearance of compact Lagrangian manifolds
that are not tori, due to the fact that the observables defining the quantum
states are noncommuting. These manifolds can be quantized by generalized
Bohr-Sommerfeld rules and yield all the correct quantum numbers. The geometry
of the classical angular momentum vectors emerges in a clear manner. Efficient
methods for computing amplitude determinants in terms of Poisson brackets are
developed and illustrated.Comment: 7 figure file
The Study of TeV Variability and Duty Cycle of Mrk 421 from 3 Years of Observations with the Milagro Observatory
TeV flaring activity with time scales as short as tens of minutes and an
orphan TeV flare have been observed from the blazar Markarian 421 (Mrk 421).
The TeV emission from Mrk 421 is believed to be produced by leptonic
synchrotron self-Compton (SSC) emission. In this scenario, correlations between
the X-ray and the TeV fluxes are expected, TeV orphan flares are hardly
explained and the activity (measured as duty cycle) of the source at TeV
energies is expected to be equal or less than that observed in X-rays if only
SSC is considered. To estimate the TeV duty cycle of Mrk 421 and to establish
limits on its variability at different time scales, we continuously observed
Mrk 421 with the Milagro observatory. Mrk 421 was detected by Milagro with a
statistical significance of 7.1 standard deviations between 2005 September 21
and 2008 March 15. The observed spectrum is consistent with previous
observations by VERITAS. We estimate the duty cycle of Mrk 421 for energies
above 1 TeV for different hypothesis of the baseline flux and for different
flare selections and we compare our results with the X-ray duty cycle estimated
by Resconi et al. 2009. The robustness of the results is discussed.Comment: 27 pages, 6 figures, ApJ accepte
TeV Gamma-Ray Sources from a Survey of the Galactic Plane with Milagro
A survey of Galactic gamma-ray sources at a median energy of ~20 TeV has been
performed using the Milagro Gamma Ray Observatory. Eight candidate sources of
TeV emission are detected with pre-trials significance in the
region of Galactic longitude and latitude
. Four of these sources, including the Crab nebula
and the recently published MGRO J2019+37, are observed with significances
after accounting for the trials involved in searching the 3800
square degree region. All four of these sources are also coincident with EGRET
sources. Two of the lower significance sources are coincident with EGRET
sources and one of these sources is Geminga. The other two candidates are in
the Cygnus region of the Galaxy. Several of the sources appear to be spatially
extended. The fluxes of the sources at 20 TeV range from ~25% of the Crab flux
to nearly as bright as the Crab.Comment: Submitted to Ap
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