4,240 research outputs found
Cluster X-ray line at from axion-like dark matter
The recently reported X-ray line signal at
from a stacked spectrum of various galaxy clusters and the Andromeda galaxy may
be originating from a decaying dark matter particle of the mass . A
light axion-like scalar is suggested as a natural candidate for dark matter and
its production mechanisms are closely examined. We show that the right amount
of axion relic density with the preferred parameters, and , can be naturally obtainable
from the decay of inflaton. If the axions were produced from the saxion decay,
it could not have constituted the total relic density due to the bound from
structure formation. Nonetheless, the saxion decay is an interesting
possibility, because the line and dark radiation can be
addressed simultaneously, being consistent with the Planck data. Small
misalignment angles of the axion, ranging between depending on the reheating temperature, can also be the source of
axion production. The model with axion misalignment can satisfy the constraints
for structure formation and iso-curvature perturbation.Comment: 14 pages, significant changes in the form, matched to the journal
versio
Diboson Excesses Demystified in Effective Field Theory Approach
We study the collider implication of a neutral resonance which decays to
several diboson final states such as , , and via a
minimal set of effective operators. We consider both CP-even and CP-odd bosonic
states with spin 0, 1, or 2. The production cross sections for the bosonic
resonance states are obtained with the effective operators involving gluons
(and quarks), and the branching fractions are obtained with the operators
responsible for the interactions with electroweak gauge bosons. We demonstrate
that each scenario allows for a broad parameter space which could accommodate
the recently-reported intriguing excesses in the ATLAS diboson final states,
and discuss how the CP states and spin information of the resonance can be
extracted at the LHC run II.Comment: 22 pages, 6 figures, main text slightly modified with results
unchange
The effects of Thomson scattering and chemical mixing on early-time light curves of double peaked type IIb supernovae
Previous numerical simulations of double-peaked SNe IIb light curves have
demonstrated that the radius and mass of the hydrogen-rich envelope of the
progenitor star can significantly influence the brightness and timescale of the
early-time light curve around the first peak. In this study, we investigate how
Thomson scattering and chemical mixing in the SN ejecta affect the optical
light curves during the early stages of the SNe IIb using radiation
hydrodynamics simulations. By comparing the results from two different
numerical codes (i.e., \stella{} and \snec{}), we find that the optical
brightness of the first peak can be reduced by more than a factor of 3 due to
the effect of Thomson scattering that causes the thermalization depth to be
located below the Rosseland-mean photosphere, compared to the corresponding
case where this effect is ignored. We also observe a short-lived plateau-like
feature lasting for a few days in the early-time optical light curves of our
models, in contrast to typical observed SNe IIb that show a quasi-linear
decrease in optical magnitudes after the first peak. A significant degree of
chemical mixing between the hydrogen-rich envelope and the helium core in SN
ejecta is required to reconcile this discrepancy between the model prediction
and observation. Meanwhile, to properly reproduce the first peak, a significant
mixing of \nifs{} into the hydrogen-rich outermost layers should be restricted.
Our findings indicate that inferring the SN IIb progenitor structure from a
simplified approach that ignores these two factors may introduce substantial
uncertainty.Comment: 28 pages, 21 figures, accepted for Ap
A study on the change in the characteristics of the gait of elderly people when somatosensory stimulation was applied to their ankle joint
The gait is the most complicated, habitual, and involuntary activity of humans and is a result of the cooperation of the central and peripheral nervous systems that harmoniously mobilize the sensory receptors, nervous system, and muscles. A sensory signal binds to a somatosensory system proprioceptor to obtain information on posture. This study was designed to analyze the change in the characteristics of a gait when stimulation is applied in the somatosensory system that controls the balance of the body. A result of the GRF obtained from the force plate and gyroscope signals from the sensor attached on ankle joint were obtained to compare the change before and after the somatosensory stimulation. The result of this study proved a potential of somatosensory stimulation in improving balance, which could be used in studies on the balance of positions and gait improvement
Strong and Reversible Adhesion of Interlocked 3D-Microarchitectures
Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the high-aspect-ratio, slender structures are mechanically less durable. In this study, we demonstrate a highly flexible and robust interlocking system that exhibits strong and reversible adhesion based on physical interlocking between three-dimensional (3D) microscale architectures. The 3D microstructures have protruding tips on their cylindrical stems, which enable tight mechanical binding between the microstructures. Based on the unique 3D architectures, the interlocking adhesives exhibit remarkable adhesion strengths in both the normal and shear directions. In addition, their adhesion is highly reversible due to the robust mechanical and structural stability of the microstructures. An analytical model is proposed to explain the measured adhesion behavior, which is in good agreement with the experimental results
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