21,075 research outputs found
Symbol detection in online handwritten graphics using Faster R-CNN
Symbol detection techniques in online handwritten graphics (e.g. diagrams and
mathematical expressions) consist of methods specifically designed for a single
graphic type. In this work, we evaluate the Faster R-CNN object detection
algorithm as a general method for detection of symbols in handwritten graphics.
We evaluate different configurations of the Faster R-CNN method, and point out
issues relative to the handwritten nature of the data. Considering the online
recognition context, we evaluate efficiency and accuracy trade-offs of using
Deep Neural Networks of different complexities as feature extractors. We
evaluate the method on publicly available flowchart and mathematical expression
(CROHME-2016) datasets. Results show that Faster R-CNN can be effectively used
on both datasets, enabling the possibility of developing general methods for
symbol detection, and furthermore, general graphic understanding methods that
could be built on top of the algorithm.Comment: Submitted to DAS-201
Neutrino signal from extended Galactic sources in IceCube
We explore the detectability of the neutrino flux from the entire Galactic
Plane or from a part of it with IceCube. We calculate the normalization and the
spectral index of the neutrino power law spectrum from different regions of the
Galactic plane, based on the observed spectral characteristics of the pion
decay gamma-ray diffuse emission observed by the Fermi/LAT telescope in the
energy band above 100 GeV. We compare the neutrino flux calculated in this way
with the sensitivity of IceCube for the detection of extended sources. Assuming
a binned extended source analysis method, we find that the only possible
evidence for neutrino emission for sources located in the Northern hemisphere
is from the Cygnus region after 20 years of exposure. For other parts of the
Galactic Plane even a 20 years exposure with IceCube is not sufficient for the
detection. Taking into account marginal significance of the detectable source
in the Cygnus region, we find a precise position and size of the source region
which optimizes the signal-to-noise ratio for neutrinos. We also calculate the
low-energy threshold above which the neutrino signal could be detected with the
highest signal-to-noise ratio. This calculation of precise source position,
size and energy range, based on the gamma-ray data, could be used to remove the
'trial factor' in the analysis of the real neutrino data of IceCube. We notice
that the diffuse neutrino emission from the inner Galactic Plane in the
Southern Hemisphere is much brighter. A neutrino detector with characteristics
equivalent to IceCube, but placed at the Northern Hemisphere (such as KM3NeT),
would detect several isolated neutrino sources in the Galactic Plane within
just 5 years exposure at 5{\sigma} level. These isolated sources of ~TeV
neutrinos would unambiguously localize sources of cosmic rays which operated
over the last 10 thousand years in the Galaxy.[abridged]Comment: submitted to A&
An exploration of hadronic interactions in blazars using IceCube
Context: Hadronic models, involving matter (proton or nuclei) acceleration in
blazar jets, imply high energy photon and neutrino emissions due to
interactions of high-energy protons with matter and/or radiation in the source
environment. Aims: This paper shows that the sensitivity of the IceCube
neutrino telescope in its 40-string configuration (IC-40) is already at the
level of constraining the parameter space of purely hadronic scenarios of
activity of blazars. Methods: Assuming that the entire source power originates
from hadronic interactions, and assuming that the models describe the data, we
estimate the expected neutrino flux from blazars based on the observed
gamma-ray flux by Fermi, simultaneously with IC-40 observations. We consider
two cases separately to keep the number of constrainable parameters at an
acceptable level: proton-proton or proton-gamma interactions are dominant.
Comparing the IC-40 sensitivity to the neutrino flux expected from some of the
brightest blazars, we constrain model parameters characterizing the parent
high-energy proton spectrum. Results: We find that when pp interactions
dominate, some constraints on the primary proton spectrum can be imposed. For
instance, for the tightest constrained source 3C 454.3, the very high energy
part of the spectra of blazars is constrained to be harder than E^-2 with
cut-off energies in the range of Ecut >10^18 eV. When interactions of
high-energy protons on soft photon fields dominate, we can find similarly tight
constraints on the proton spectrum parameters. [abridged]Comment: accepted for publication in A&
Triatomic continuum resonances for large negative scattering lengths
We study triatomic systems in the regime of large negative scattering lengths
which may be more favorable for the formation of condensed trimers in trapped
ultracold monoatomic gases as the competition with the weakly bound dimers is
absent. The manipulation of the scattering length can turn an excited weakly
bound Efimov trimer into a continuum resonance. Its energy and width are
described by universal scaling functions written in terms of the scattering
length and the binding energy, , of the shallowest triatomic molecule. For
the excited Efimov state turns into a
continuum resonance.Comment: 4 pages, 4 figure
Unified description of seagull cancellations and infrared finiteness of gluon propagators
We present a generalized theoretical framework for dealing with the important
issue of dynamical mass generation in Yang-Mills theories, and, in particular,
with the infrared finiteness of the gluon propagators, observed in a multitude
of recent lattice simulations. Our analysis is manifestly gauge-invariant, in
the sense that it preserves the transversality of the gluon self-energy, and
gauge-independent, given that the conclusions do not depend on the choice of
the gauge-fixing parameter within the linear covariant gauges. The central
construction relies crucially on the subtle interplay between the Abelian Ward
identities satisfied by the nonperturbative vertices and a special integral
identity that enforces a vast number of 'seagull cancellations' among the one-
and two-loop dressed diagrams of the gluon Schwinger-Dyson equation. The key
result of these considerations is that the gluon propagator remains rigorously
massless, provided that the vertices do not contain (dynamical) massless poles.
When such poles are incorporated into the vertices, under the pivotal
requirement of respecting the gauge symmetry of the theory, the terms
comprising the Ward identities conspire in such a way as to still enforce the
total annihilation of all quadratic divergences, inducing, at the same time,
residual contributions that account for the saturation of gluon propagators in
the deep infrared.Comment: 40 pages, 7 figures; v2: typos corrected, version matching the
published on
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