19,044 research outputs found
Possible High-Energy Neutrino and Photon Signals from Gravitational Wave Bursts due to Double Neutron Star Mergers
As the technology of gravitational-wave and neutrino detectors becomes
increasingly mature, a multi-messenger era of astronomy is ushered in. Advanced
gravitational wave detectors are close to making a ground-breaking discovery of
gravitational wave bursts (GWBs) associated with mergers of double neutron
stars (NS-NS). It is essential to study the possible electromagnetic (EM) and
neutrino emission counterparts of these GWBs. Recent observations and numerical
simulations suggest that at least a fraction of NS-NS mergers may leave behind
a massive millisecond magnetar as the merger product. Here we show that protons
accelerated in the forward shock powered by a magnetar wind pushing the ejecta
launched during the merger process would interact with photons generated in the
dissipating magnetar wind and emit high energy neutrinos and photons. We
estimate the typical energy and fluence of the neutrinos from such a scenario.
We find that PeV neutrinos could be emitted from the shock front as long
as the ejecta could be accelerated to a relativistic speed. The diffuse
neutrino flux from these events, even under the most optimistic scenarios, is
too low to account for the two events announced by the IceCube Collaboration,
but it is only slightly lower than the diffuse flux of GRBs, making it an
important candidate for the diffuse background of PeV neutrinos. The
neutron-pion decay of these events make them a moderate contributor to the
sub-TeV gamma-ray diffuse background.Comment: Accepted for publication in PRD, minor revisio
Bright broad-band afterglows of gravitational wave bursts from mergers of binary neutron stars
If double neutron star mergers leave behind a massive magnetar rather than a
black hole, a bright early afterglow can follow the gravitational wave burst
(GWB) even if there is no short gamma-ray burst (SGRB) - GWB association or
there is an association but the SGRB does not beam towards earth. Besides
directly dissipating the proto-magnetar wind as suggested by Zhang, we here
suggest that the magnetar wind could push the ejecta launched during the merger
process, and under certain conditions, would reach a relativistic speed. Such a
magnetar-powered ejecta, when interacting with the ambient medium, would
develop a bright broad-band afterglow due to synchrotron radiation. We study
this physical scenario in detail, and present the predicted X-ray, optical and
radio light curves for a range of magnetar and ejecta parameters. We show that
the X-ray and optical lightcurves usually peak around the magnetar spindown
time scale (10^3-10^5s), reaching brightness readily detectable by wide-field
X-ray and optical telescopes, and remain detectable for an extended period. The
radio afterglow peaks later, but is much brighter than the case without a
magnetar energy injection. Therefore, such bright broad-band afterglows, if
detected and combined with GWBs in the future, would be a probe of massive
millisecond magnetars and stiff equation-of-state for nuclear matter.Comment: ApJ, in pres
What-and-Where to Match: Deep Spatially Multiplicative Integration Networks for Person Re-identification
Matching pedestrians across disjoint camera views, known as person
re-identification (re-id), is a challenging problem that is of importance to
visual recognition and surveillance. Most existing methods exploit local
regions within spatial manipulation to perform matching in local
correspondence. However, they essentially extract \emph{fixed} representations
from pre-divided regions for each image and perform matching based on the
extracted representation subsequently. For models in this pipeline, local finer
patterns that are crucial to distinguish positive pairs from negative ones
cannot be captured, and thus making them underperformed. In this paper, we
propose a novel deep multiplicative integration gating function, which answers
the question of \emph{what-and-where to match} for effective person re-id. To
address \emph{what} to match, our deep network emphasizes common local patterns
by learning joint representations in a multiplicative way. The network
comprises two Convolutional Neural Networks (CNNs) to extract convolutional
activations, and generates relevant descriptors for pedestrian matching. This
thus, leads to flexible representations for pair-wise images. To address
\emph{where} to match, we combat the spatial misalignment by performing
spatially recurrent pooling via a four-directional recurrent neural network to
impose spatial dependency over all positions with respect to the entire image.
The proposed network is designed to be end-to-end trainable to characterize
local pairwise feature interactions in a spatially aligned manner. To
demonstrate the superiority of our method, extensive experiments are conducted
over three benchmark data sets: VIPeR, CUHK03 and Market-1501.Comment: Published at Pattern Recognition, Elsevie
Deep Adaptive Feature Embedding with Local Sample Distributions for Person Re-identification
Person re-identification (re-id) aims to match pedestrians observed by
disjoint camera views. It attracts increasing attention in computer vision due
to its importance to surveillance system. To combat the major challenge of
cross-view visual variations, deep embedding approaches are proposed by
learning a compact feature space from images such that the Euclidean distances
correspond to their cross-view similarity metric. However, the global Euclidean
distance cannot faithfully characterize the ideal similarity in a complex
visual feature space because features of pedestrian images exhibit unknown
distributions due to large variations in poses, illumination and occlusion.
Moreover, intra-personal training samples within a local range are robust to
guide deep embedding against uncontrolled variations, which however, cannot be
captured by a global Euclidean distance. In this paper, we study the problem of
person re-id by proposing a novel sampling to mine suitable \textit{positives}
(i.e. intra-class) within a local range to improve the deep embedding in the
context of large intra-class variations. Our method is capable of learning a
deep similarity metric adaptive to local sample structure by minimizing each
sample's local distances while propagating through the relationship between
samples to attain the whole intra-class minimization. To this end, a novel
objective function is proposed to jointly optimize similarity metric learning,
local positive mining and robust deep embedding. This yields local
discriminations by selecting local-ranged positive samples, and the learned
features are robust to dramatic intra-class variations. Experiments on
benchmarks show state-of-the-art results achieved by our method.Comment: Published on Pattern Recognitio
The possible molecular state and its radiative decay
Recently, several exotic bosons have been confirmed as multi-quark states,
but there are violent disputes about their inner structures, namely if they are
molecular states or tetraquarks, or even mixtures of the two structures. It
would be interesting to experimentally search for non-strange four-quark states
with open charm or bottom which are lighter than or .
Reasonable arguments indicate that they are good candidates of pure molecular
states or because pions are the lightest boson. Both and
bound states do not decay via strong interaction. The molecule
may decay into by radiating a photon, whereas molecule can only
decay via weak interaction. In this paper we explore the mass spectra of
molecular statesby solving the corresponding B-S equation. Then the rate of
radiative decay is calculated
and our numerical results indicate that the processes can be measured by the
future experiment. We also briefly discuss the case, due to the
constraint of the final state phase space, it can only decay via weak
interaction.Comment: 12 pages, 3 figures, 3 table
The effects of perceived brand globalness on consumer responses to brand failures
Even big companies cannot guarantee their brands never ever fail customers. Recently the brand failures of Toyota taught us a vivid lesson that a brand takes decades to be built up but to be ruined overnight. Although, the advantages of building global brands are well recognized in literature, the superiorities of global brands in brand failure context are not yet studied. This study aims to investigate the effects of perceived brand globalness (PBG) on consumer affective and behavioral responses to brand failures. Global brands are perceived superior to local brands due to factors like higher quality perceptions and prestige feelings. Based on attribution theory, consumers are expected to have less negative responses to the failure of a brand which has a higher (vs. lower) PBG. Two studies were conducted to test the proposed hypotheses. Both studies were 2 (high PBG vs. low PBG brand) × 2 (failure present vs. absent) between subjects factorial designs. More than 200 respondents participated in the experiments. Study 1 examined the effects of PBG on consumer responses to fictitious brands. In order to increase the generalizability of research, Study 2 used established brands to find out the effects of PBG on consumer responses while controlling the confounding variables of brand familiarity and brand equity of the selected established brands. The results indicate that the more a brand is perceived global, the less negative responses consumers have toward the failures. Moreover, this thesis examines the moderating role of consumer ethnocentrism on the relationship between PBG and consumer responses. The proposed hypotheses are generally supported. The findings enrich the literature and benefit the marketing practitioners by broadening their views of building global brands
Monetary Policy and Exchange Rate Regime: Proposal for a Small and Less Developed Economy
We investigate monetary policy under the assumption that a country’s capital market is “open” under the WTO framework while the exchange rate is fixed. Our purpose is to determine if it is possible in this case for the economy to maintain an effective monetary policy for stabilizing the domestic economy. For this, we suggest two institutional restrictions. Given the restrictions, we demonstrate within a macro-dynamic model that monetary policy can still be effective. The implication of such an institutional design for an exchange rate regime is also discussed with special reference to small and less development economies.open economy trilemma; macroeconomic stability; exchange rate regime
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