2,989 research outputs found
Exotic hadrons in s-wave chiral dynamics
We study s-wave scattering of a hadron and a Nambu-Goldstone boson induced by
the model-independent low energy interaction in the flavor SU(3) symmetric
limit. Establishing the general structure of the low energy interaction based
on group theoretical arguments, we find that the interaction in the exotic
channels are in most cases repulsive, and that for possible attractive channels
the interaction strengths are weak and uniquely given independent of channel.
Solving the scattering problem with this interaction, we show that the
attraction in the exotic channels is not strong enough to generate a bound
state from the physically known target hadrons. We also find that there are no
attractive interaction in the exotic channels in large Nc limit.Comment: RevTeX4, 4 pages, 1 figure, 2 tables, typos correcte
Weak value amplification in a shot-noise limited interferometer
We study the weak-value amplification (WVA) in a phase measurement with an
optical interferometer in which shot noise limits the sensitivity. We compute
the signal and the shot noise including the full-order interaction terms of the
WVA, and show that the shot-noise contribution to a phase shift in a pointer
variable is always larger than the final variance of the pointer variable. This
yields difference in estimating noise level up to a factor of 1.5. To clarify
an advantage for practical uses of the WVA, we discuss signal-to-noise ratio
and its optimization in the presence of the shot noise.Comment: 6 pages, 4 figure
Absence of contagious yawning in children with autism spectrum disorder
This study is the first to report the disturbance of contagious yawning in individuals with autism spectrum disorder (ASD). Twenty-four children with ASD as well as 25 age-matched typically developing (TD) children observed video clips of either yawning or control mouth movements. Yawning video clips elicited more yawns in TD children than in children with ASD, but the frequency of yawns did not differ between groups when they observed control video clips. Moreover, TD children yawned more during or after the yawn video clips than the control video clips, but the type of video clips did not affect the amount of yawning in children with ASD. Current results suggest that contagious yawning is impaired in ASD, which may relate to their impairment in empathy. It supports the claim that contagious yawning is based on the capacity for empathy
Study of exotic hadrons in S-wave scatterings induced by chiral interaction in the flavor symmetric limit
We study s-wave bound states of a hadron and a light pseudoscalar meson
induced by the Weinberg-Tomozawa (WT) interaction in the flavor SU(3) symmetric
limit. The WT interaction is a driving force to generate quasibound states
dynamically in the chiral unitary approaches. The strength and sign of the WT
interaction are determined only by the group theoretical structure of the
target hadrons, and we present a general expression of the strengths for the
flavor SU(3) case. We show that, for the channels which are more exotic than
the target, the interaction is repulsive in most cases, and the strength of the
attractive interaction is universal for any possible target states. We
demonstrate that the attractive coupling is not strong enough to generate an
exotic state from the physically known masses of target hadrons. In addition,
we also find a nontrivial Nc dependence of the coupling strengths. We show that
the channels which are attractive at Nc=3 changes into repulsive ones for large
Nc, and, therefore, no attractive interaction exists in exotic channels in the
large-Nc limit.Comment: RevTeX4, 16 pages, 5 figure, 6 tables, This manuscript is a full
paper of Phys. Rev. Lett. 97, 192002 (hep-ph/0609014), typos corrected, final
versio
Cosmological test of gravity with polarizations of stochastic gravitational waves around 0.1-1 Hz
In general relativity, a gravitational wave has two polarization modes
(tensor mode), but it could have additional polarizations (scalar and vector
modes) in the early stage of the universe, where the general relativity may not
strictly hold and/or the effect of higher-dimensional gravity may become
significant. In this paper, we discuss how to detect extra-polarization modes
of stochastic gravitational wave background (GWB), and study the separability
of each polarization using future space-based detectors such as BBO and DECIGO.
We specifically consider two plausible setups of the spacecraft constellations
consisting of two and four clusters, and estimate the sensitivity to each
polarization mode of GWBs. We find that a separate detection of each
polarization mode is rather sensitive to the geometric configuration and
distance between clusters and that the clusters should be, in general,
separated by an appropriate distance. This seriously degrades the signal
sensitivity, however, for suitable conditions, space-based detector can
separately detect scalar, vector and tensor modes of GWBs with energy density
as low as ~10^-15.Comment: 16 pages, 11 figure
Non-linear Evolution of Matter Power Spectrum in Modified Theory of Gravity
We present a formalism to calculate the non-linear matter power spectrum in
modified gravity models that explain the late-time acceleration of the Universe
without dark energy. Any successful modified gravity models should contain a
mechanism to recover General Relativity (GR) on small scales in order to avoid
the stringent constrains on deviations from GR at solar system scales. Based on
our formalism, the quasi non-linear power spectrum in the
Dvali-Gabadadze-Porratti (DGP) braneworld models and gravity models are
derived by taking into account the mechanism to recover GR properly. We also
extrapolate our predictions to fully non-linear scales using the Parametrized
Post Friedmann (PPF) framework. In gravity models, the predicted
non-linear power spectrum is shown to reproduce N-body results. We find that
the mechanism to recover GR suppresses the difference between the modified
gravity models and dark energy models with the same expansion history, but the
difference remains large at weakly non-linear regime in these models. Our
formalism is applicable to a wide variety of modified gravity models and it is
ready to use once consistent models for modified gravity are developed.Comment: 25 pages, 8 figures, comparison to N-body simulations in DGP added,
published in PR
Observation of Plasma Hole in an ECR Ar Plasma
The first experimental observation of a plasma hole structure in an ECR argon plasma is reported. The plasma hole is a cylindrical density cavity, which is formed spontaneously in the center of the plasma. The steep density gradient between the hole plasma and the ambient plasma is sustained by a thin interfacial layer, the width of which is a few ion Larmor radii. Supersonic rotation is found over the large cross-sectional area of Ar plasma hole. The axial flow can also exceed ion sound speed. Spectral measurements revealed that the neutral density profile exhibits a hole structure as well as that in ion density, the diameter of which is much shorter than the mean free path of neutral particles
Cultural background modulates how we look at other persons' gaze
The current study investigated the role of cultural norms on the development of face-scanning. British and Japanese adultsâ eye movements were recorded while they observed avatar faces moving their mouth, and then their eyes toward or away from the participants. British participants fixated more on the mouth, which contrasts with Japanese participants fixating mainly on the eyes. Moreover, eye fixations of British participants were less affected by the gaze shift of the avatar than Japanese participants, who shifted their fixation to the corresponding direction of the avatarâs gaze. Results are consistent with the Western cultural norms that value the maintenance of eye contact, and the Eastern cultural norms that require flexible use of eye contact and gaze aversion
Fast Vacuum Decay into Quark Pairs in Strong Color Electric and Magnetic Fields
We study quark-pair creations in strong color electromagnetic fields. We
point out that, for massless quarks, the vacuum persistency probability per
unit space-time volume is zero, i.e., the quark-pair creation rate w is
infinite, in general homogeneous color electromagnetic fields, while it is
finite when the color magnetic field is absent. We find that the contribution
from the lowest Landau level (LLL) dominates this phenomenon. With an effective
theory of the LLL projection, we also discuss dynamics of the vacuum decay,
taking into account the back reaction of pair creations.Comment: 4 pages, 1 figure, contribution to the proceedings of International
conference on the structure of baryons (BARYONS'10), RCNP, Osaka, Japan, Dec.
7-11, 2010; fig.2 delete
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