286 research outputs found
A dipole anisotropy of galaxy distribution: Does the CMB rest-frame exist in the local universe?
The peculiar motion of the Earth causes a dipole anisotropy modulation in the
distant galaxy distribution due to the aberration effect. However, the
amplitude and angular direction of the effect is not necessarily the same as
those of the cosmic microwave background (CMB) dipole anisotropy due to the
growth of cosmic structures. In other words exploring the aberration effect may
give us a clue to the horizon-scale physics perhaps related to the cosmic
acceleration. In this paper we develop a method to explore the dipole angular
modulation from the pixelized galaxy data on the sky properly taking into
account the covariances due to the shot noise and the intrinsic galaxy
clustering contamination as well as the partial sky coverage. We applied the
method to the galaxy catalogs constructed from the Sloan Digital Sky Survey
(SDSS) Data Release 6 data. After constructing the four galaxy catalogs that
are different in the ranges of magnitudes and photometric redshifts to study
possible systematics, we found that the most robust sample against systematics
indicates no dipole anisotropy in the galaxy distribution. This finding is
consistent with the expectation from the concordance Lambda-dominated cold dark
matter model. Finally we argue that an almost full-sky galaxy survey such as
LSST may allow for a significant detection of the aberration effect of the CMB
dipole having the precision of constraining the angular direction to ~ 20
degrees in radius. Assuming a hypothetical LSST galaxy survey, we find that
this method can confirm or reject the result implied from a stacked analysis of
the kinetic Sunyaev-Zel'dovich effect of X-ray luminous clusters in Kashlinsky
et al. (2008,2009) if the implied cosmic bulk flow is not extended out to the
horizon.Comment: 20 pages, 11 figures; 24 pages, added a couple of references and 2
figures. Revised version in response to the referee's comments. Resubmitted
to Phys. Rev.
Worm algorithms for classical statistical models
We show that high-temperature expansions may serve as a basis for the novel
approach to efficient Monte Carlo simulations. "Worm" algorithms utilize the
idea of updating closed path configurations (produced by high-temperature
expansions) through the motion of end points of a disconnected path. An amazing
result is that local, Metropolis-type schemes may have dynamical critical
exponents close to zero (i.e., their efficiency is comparable to the best
cluster methods). We demonstrate this by calculating finite size scaling of the
autocorrelation time for various (six) universality classes.Comment: 4 pages, latex, 2 figure
Influence of through-flow on linear pattern formation properties in binary mixture convection
We investigate how a horizontal plane Poiseuille shear flow changes linear
convection properties in binary fluid layers heated from below. The full linear
field equations are solved with a shooting method for realistic top and bottom
boundary conditions. Through-flow induced changes of the bifurcation thresholds
(stability boundaries) for different types of convective solutions are deter-
mined in the control parameter space spanned by Rayleigh number, Soret coupling
(positive as well as negative), and through-flow Reynolds number. We elucidate
the through-flow induced lifting of the Hopf symmetry degeneracy of left and
right traveling waves in mixtures with negative Soret coupling. Finally we
determine with a saddle point analysis of the complex dispersion relation of
the field equations over the complex wave number plane the borders between
absolute and convective instabilities for different types of perturbations in
comparison with the appropriate Ginzburg-Landau amplitude equation
approximation. PACS:47.20.-k,47.20.Bp, 47.15.-x,47.54.+rComment: 19 pages, 15 Postscript figure
Large-Scale Anisotropic Correlation Function of SDSS Luminous Red Galaxies
We study the large-scale anisotropic two-point correlation function using
46,760 luminous red galaxies at redshifts 0.16 -- 0.47 from the Sloan Digital
Sky Survey. We measure the correlation function as a function of separations
parallel and perpendicular to the line-of-sight in order to take account of
anisotropy of the large-scale structure in redshift space. We find a slight
signal of baryonic features in the anisotropic correlation function, i.e., a
``baryon ridge'' which corresponds to a baryon acoustic peak in the spherically
averaged correlation function which has already been reported using the same
sample. The baryon ridge has primarily a spherical structure with a known
radius in comoving coordinates. It enables us to divide the redshift distortion
effects into dynamical and geometrical components and provides further
constraints on cosmological parameters, including the dark energy
equation-of-state. With an assumption of a flat cosmology, we find
the best-fit values of and
(68% C.L.) when we use the overall
shape of the anisotropic correlation function of 40 including a
scale of baryon acoustic oscillations. When an additional assumption
is adopted, we obtain and . These constraints
are estimated only from our data of the anisotropic correlation function, and
they agree quite well with values both from the cosmic microwave background
(CMB) anisotropies and from other complementary statistics using the LRG
sample. With the CMB prior from the 3 year WMAP results, we give stronger
constraints on those parameters.Comment: 11 pages, 9 figures, 1 table, typo corrected, references added with
respect to published versio
Influence of the Soret effect on convection of binary fluids
Convection in horizontal layers of binary fluids heated from below and in
particular the influence of the Soret effect on the bifurcation properties of
extended stationary and traveling patterns that occur for negative Soret
coupling is investigated theoretically. The fixed points corresponding to these
two convection structures are determined for realistic boundary conditions with
a many mode Galerkin scheme for temperature and concentration and an accurate
one mode truncation of the velocity field. This solution procedure yields the
stable and unstable solutions for all stationary and traveling patterns so that
complete phase diagrams for the different convection types in typical binary
liquid mixtures can easily be computed. Also the transition from weakly to
strongly nonlinear states can be analyzed in detail. An investigation of the
concentration current and of the relevance of its constituents shows the way
for a simplification of the mode representation of temperature and
concentration field as well as for an analytically manageable few mode
description.Comment: 30 pages, 12 figure
Nonequilibrium relaxation of the two-dimensional Ising model: Series-expansion and Monte Carlo studies
We study the critical relaxation of the two-dimensional Ising model from a
fully ordered configuration by series expansion in time t and by Monte Carlo
simulation. Both the magnetization (m) and energy series are obtained up to
12-th order. An accurate estimate from series analysis for the dynamical
critical exponent z is difficult but compatible with 2.2. We also use Monte
Carlo simulation to determine an effective exponent, z_eff(t) = - {1/8} d ln t
/d ln m, directly from a ratio of three-spin correlation to m. Extrapolation to
t = infinity leads to an estimate z = 2.169 +/- 0.003.Comment: 9 pages including 2 figure
Cross-Correlation between UHECR Arrival Distribution and Large-Scale Structure
We investigate correlation between the arrival directions of
ultra-high-energy cosmic rays (UHECRs) and the large-scale structure (LSS) of
the Universe by using statistical quantities which can find the angular scale
of the correlation. The Infrared Astronomical Satellite Point Source Redshift
Survey (IRAS PSCz) catalog of galaxies is adopted for LSS. We find a positive
correlation of the highest energy events detected by the Pierre Auger
Observatory (PAO) with the IRAS galaxies inside within the angular
scale of . This positive correlation observed in the southern
sky implies that a significant fraction of the highest energy events comes from
nearby extragalactic objects. We also analyze the data of the Akeno Giant Air
Shower Array (AGASA) which observed the northern hemisphere, but the obvious
signals of positive correlation with the galaxy distribution are not found.
Since the exposure of the AGASA is smaller than the PAO, the cross-correlation
in the northern sky should be tested using a larger number of events detected
in the future. We also discuss the correlation using the all-sky combined data
sets of both the PAO and AGASA, and find a significant correlation within . These angular scales can constrain several models of intergalactic
magnetic field. These cross-correlation signals can be well reproduced by a
source model in which the distribution of UHECR sources is related to the IRAS
galaxies.Comment: 21 pages,7 figure
New Dynamic Monte Carlo Renormalization Group Method
The dynamical critical exponent of the two-dimensional spin-flip Ising model
is evaluated by a Monte Carlo renormalization group method involving a
transformation in time. The results agree very well with a finite-size scaling
analysis performed on the same data. The value of is
obtained, which is consistent with most recent estimates
Targeting of plasminogen activator inhibitor-1 activity promotes elimination of chronic myeloid leukemia stem cells
Therapeutic strategies that target leukemic stem cells (LSCs) provide potential advantages in the treatment of chronic myeloid leukemia (CML). Here, we show that selective blockade of plasminogen activator inhibitor-1 (PAI-1) enhances the susceptibility of CML-LSCs to tyrosine kinase inhibitor (TKI), which facilitates the eradication of CML-LSCs and leads to sustained remission of the disease. We demonstrated for the first time that TGF-β-PAI-1 axis was selectively augmented in CML-LSCs in the bone marrow (BM), whereby protecting CML-LSCs from TKI treatment. Furthermore, the combined administration of TKI plus a PAI-1 inhibitor, in a mouse model of CML, significantly enhanced the eradication of CML cells in the BM and prolonged the survival of CML mice. The combined therapy of imatinib and a PAI-1 inhibitor prevented the recurrence of CML-like disease in serially transplanted recipients, indicating the elimination of CML-LSCs. Interestingly, PAI-1 inhibitor treatment augmented membrane-type matrix metalloprotease-1 (MT1-MMP)-dependent motility of CML-LSCs, and the anti-CML effect of PAI-1 inhibitor was extinguished by the neutralizing antibody for MT1-MMP, underlining the mechanistic importance of MT1-MMP. Our findings provide evidence of, and a rationale for, a novel therapeutic tactic, based on the blockade of PAI-1 activity, for CML patients
The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: Analysis of potential systematics
We analyze the density field of galaxies observed by the Sloan Digital Sky
Survey (SDSS)-III Baryon Oscillation Spectroscopic Survey (BOSS) included in
the SDSS Data Release Nine (DR9). DR9 includes spectroscopic redshifts for over
400,000 galaxies spread over a footprint of 3,275 deg^2. We identify,
characterize, and mitigate the impact of sources of systematic uncertainty on
large-scale clustering measurements, both for angular moments of the
redshift-space correlation function and the spherically averaged power
spectrum, P(k), in order to ensure that robust cosmological constraints will be
obtained from these data. A correlation between the projected density of stars
and the higher redshift (0.43 < z < 0.7) galaxy sample (the `CMASS' sample) due
to imaging systematics imparts a systematic error that is larger than the
statistical error of the clustering measurements at scales s > 120h^-1Mpc or k
< 0.01hMpc^-1. We find that these errors can be ameliorated by weighting
galaxies based on their surface brightness and the local stellar density. We
use mock galaxy catalogs that simulate the CMASS selection function to
determine that randomly selecting galaxy redshifts in order to simulate the
radial selection function of a random sample imparts the least systematic error
on correlation function measurements and that this systematic error is
negligible for the spherically averaged correlation function. The methods we
recommend for the calculation of clustering measurements using the CMASS sample
are adopted in companion papers that locate the position of the baryon acoustic
oscillation feature (Anderson et al. 2012), constrain cosmological models using
the full shape of the correlation function (Sanchez et al. 2012), and measure
the rate of structure growth (Reid et al. 2012). (abridged)Comment: Matches version accepted by MNRAS. Clarifications and references have
been added. See companion papers that share the "The clustering of galaxies
in the SDSS-III Baryon Oscillation Spectroscopic Survey:" titl
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