3,911 research outputs found
Magnification effect on the detection of primordial non-Gaussianity from photometric surveys
We present forecast results for constraining the primordial non-Gaussianity
from photometric surveys through a large-scale enhancement of the galaxy
clustering amplitude. In photometric surveys, the distribution of observed
galaxies at high redshifts suffers from the gravitational-lensing
magnification, which systematically alters the number density for
magnitude-limited galaxy samples. We estimate size of the systematic bias in
the best-fit cosmological parameters caused by the magnification effect,
particularly focusing on the primordial non-Gaussianity. For upcoming deep
and/or wide photometric surveys like HSC, DES and LSST, the best-fit value of
the non-Gaussian parameter, fNL, obtained from the galaxy count data is highly
biased, and the true values of fNL would typically go outside the 3-sigma error
of the biased confidence region, if we ignore the magnification effect in the
theoretical template of angular power spectrum. The additional information from
cosmic shear data helps not only to improve the constraint, but also to reduce
the systematic bias. As a result, the size of systematic bias on fNL would
become small enough compared to the expected 1-sigma error for HSC and DES, but
it would be still serious for deep surveys with z_m > 1.5, like LSST.
Tomographic technique improves the constraint on fNL by a factor of 2-3
compared to the one without tomography, but the systematic bias would increase.Comment: 12 pages, 10 figure
Pseudoparticle Multipole Method: A Simple Method to Implement High-Accuracy Treecode
In this letter we describe the pseudoparticle multipole method (P2M2), a new
method to express multipole expansion by a distribution of pseudoparticles. We
can use this distribution of particles to calculate high order terms in both
the Barnes-Hut treecode and FMM. The primary advantage of P2M2 is that it works
on GRAPE. GRAPE is a special-purpose hardware for the calculation of
gravitational force between particles. Although the treecode has been
implemented on GRAPE, we could handle terms only up to dipole, since GRAPE can
calculate forces from point-mass particles only. Thus the calculation cost
grows quickly when high accuracy is required. With P2M2, the multipole
expansion is expressed by particles, and thus GRAPE can calculate high order
terms. Using P2M2, we implemented an arbitrary-order treecode on GRAPE-4.
Timing result shows GRAPE-4 accelerates the calculation by a factor between 10
(for low accuracy) to 150 (for high accuracy). Even on general-purpose
programmable computers, our method offers the advantage that the mathematical
formulae and therefore the actual program is much simpler than that of the
direct implementation of multipole expansion.Comment: 6 pages, 4 figures, latex, submitted to ApJ Letter
Gluon propagators and center vortices at finite temperature
We study influence of center vortices on infrared properties of gluons in the
deconfinement phase of quenched QCD. We observe a significant suppression of
the magnetic component of the gluon propagator in the low-momentum region after
the vortices are removed from the gluon configurations. The propagator of the
electric gluon stays almost unaffected by the vortex removal. Our results
demonstrate that the center vortices are responsible for important
nonperturbative properties of the magnetic component of the quark-gluon plasma.Comment: 7 pages, 8 figures, talk presented at 27th International Symposium on
Lattice Field Theory (Lattice 2009), Beijing, 26-31 Jul 200
A Closure Theory for Non-linear Evolution of Cosmological Power Spectra
We apply a non-linear statistical method in turbulence to the cosmological
perturbation theory and derive a closed set of evolution equations for matter
power spectra. The resultant closure equations consistently recover the
one-loop results of standard perturbation theory and beyond that, it is still
capable of treating the non-linear evolution of matter power spectra. We find
the exact integral expressions for the solutions of closure equations. These
analytic expressions coincide with the renormalized one-loop results presented
by Crocce & Scoccimarro (2006,2007). By constructing the non-linear propagator,
we analytically evaluate the non-linear matter power spectra based on the
first-order Born approximation of the integral expressions and compare it with
those of the renormalized perturbation theory.Comment: 22 pages, 4 figures, accepted for publication in Ap
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
RegPT: Direct and fast calculation of regularized cosmological power spectrum at two-loop order
We present a specific prescription for the calculation of cosmological power
spectra, exploited here at two-loop order in perturbation theory (PT), based on
the multi-point propagator expansion. In this approach power spectra are
constructed from the regularized expressions of the propagators that reproduce
both the resummed behavior in the high-k limit and the standard PT results at
low-k. With the help of N-body simulations, we show that such a construction
gives robust and accurate predictions for both the density power spectrum and
the correlation function at percent-level in the weakly non-linear regime. We
then present an algorithm that allows accelerated evaluations of all the
required diagrams by reducing the computational tasks to one-dimensional
integrals. This is achieved by means of pre-computed kernel sets defined for
appropriately chosen fiducial models. The computational time for two-loop
results is then reduced from a few minutes, with the direct method, to a few
seconds with the fast one. The robustness and applicability of this method are
tested against the power spectrum cosmic emulator from which a wide variety of
cosmological models can be explored. The fortran program with which direct and
fast calculations of power spectra can be done, RegPT, is publicly released as
part of this paper.Comment: 28 pages, 15 figure
Exotic baryons from a heavy meson and a nucleon - Positive parity states -
We study heavy baryons with exotic flavor quantum numbers formed by a heavy
meson and a nucleon (DbarN and BN) with positive parity. One pion exchange
interaction, providing a tensor force, dominates as a long range force to bind
the DbarN and BN ystems. In the heavy quark mass limit, pseudoscalar meson and
vector meson are degenerate and the binding mechanism by the tensor force
analogous to that in the nuclear systems becomes important. As a result, we
obtain the DbarN and BN resonant states in the J^P=1/2^+, 3/2^+ and 5/2^+
channels with I=0
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
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
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