18,199 research outputs found
Decays of and into vector and pseudoscalar meson and the pseudoscalar glueball- mixing
We introduce a parametrization scheme for where
the effects of SU(3) flavor symmetry breaking and doubly OZI-rule violation
(DOZI) can be parametrized by certain parameters with explicit physical
interpretations. This scheme can be used to clarify the glueball-
mixing within the pseudoscalar mesons. We also include the contributions from
the electromagnetic (EM) decays of and via
. Via study of the isospin violated
channels, such as , ,
and , reasonable constraints on the EM decay
contributions are obtained. With the up-to-date experimental data for
, and , etc, we arrive at a consistent description of the mentioned
processes with a minimal set of parameters. As a consequence, we find that
there exists an overall suppression of the form factors,
which sheds some light on the long-standing " puzzle". By determining
the glueball components inside the pseudoscalar and in
three different glueball- mixing schemes, we deduce that the lowest
pseudoscalar glueball, if exists, has rather small component, and it
makes the a preferable candidate for glueball.Comment: Revised version to appear on J. Phys. G; An error in the code was
corrected. There's slight change to the numerical results, while the
conclusion is intac
Lagrangian bias in the local bias model
It is often assumed that the halo-patch fluctuation field can be written as a
Taylor series in the initial Lagrangian dark matter density fluctuation field.
We show that if this Lagrangian bias is local, and the initial conditions are
Gaussian, then the two-point cross-correlation between halos and mass should be
linearly proportional to the mass-mass auto-correlation function. This
statement is exact and valid on all scales; there are no higher order
contributions, e.g., from terms proportional to products or convolutions of
two-point functions, which one might have thought would appear upon truncating
the Taylor series of the halo bias function. In addition, the auto-correlation
function of locally biased tracers can be written as a Taylor series in the
auto-correlation function of the mass; there are no terms involving, e.g.,
derivatives or convolutions. Moreover, although the leading order coefficient,
the linear bias factor of the auto-correlation function is just the square of
that for the cross-correlation, it is the same as that obtained from expanding
the mean number of halos as a function of the local density only in the
large-scale limit. In principle, these relations allow simple tests of whether
or not halo bias is indeed local in Lagrangian space. We discuss why things are
more complicated in practice. We also discuss our results in light of recent
work on the renormalizability of halo bias, demonstrating that it is better to
renormalize than not. We use the Lognormal model to illustrate many of our
findings.Comment: 14 pages, published on JCA
New Angle on the Strong CP and Chiral Symmetry Problems from a Rotating Mass Matrix
It is shown that when the mass matrix changes in orientation (rotates) in
generation space for changing energy scale, then the masses of the lower
generations are not given just by its eigenvalues. In particular, these masses
need not be zero even when the eigenvalues are zero. In that case, the strong
CP problem can be avoided by removing the unwanted term by a chiral
transformation in no contradiction with the nonvanishing quark masses
experimentally observed. Similarly, a rotating mass matrix may shed new light
on the problem of chiral symmetry breaking. That the fermion mass matrix may so
rotate with scale has been suggested before as a possible explanation for
up-down fermion mixing and fermion mass hierarchy, giving results in good
agreement with experiment.Comment: 14 page
The Far-Infrared Background Correlation with CMB Lensing
The intervening large--scale structure distorts cosmic microwave background
(CMB) anisotropies via gravitational lensing. The same large--scale structure,
traced by dusty star--forming galaxies, also induces anisotropies in the
far--infrared background (FIRB). We investigate the resulting inter--dependence
of the FIRB and CMB with a halo model for the FIRB. In particular, we calculate
the cross--correlation between the lensing potential and the FIRB. The lensing
potential can be quadratically estimated from CMB temperature and/or
polarization maps. We show that the cross--correlation can be measured with
high signal--to--noise with data from the Planck Surveyor. We discuss how such
a measurement can be used to understand the nature of FIRB sources and their
relation to the distribution of dark matter.Comment: 9 pages, 5 figures, submitted to Ap
Gravity and Large-Scale Non-local Bias
The relationship between galaxy and matter overdensities, bias, is most often
assumed to be local. This is however unstable under time evolution, we provide
proofs under several sets of assumptions. In the simplest model galaxies are
created locally and linearly biased at a single time, and subsequently move
with the matter (no velocity bias) conserving their comoving number density (no
merging). We show that, after this formation time, the bias becomes unavoidably
non-local and non-linear at large scales. We identify the non-local
gravitationally induced fields in which the galaxy overdensity can be expanded,
showing that they can be constructed out of the invariants of the deformation
tensor (Galileons). In addition, we show that this result persists if we
include an arbitrary evolution of the comoving number density of tracers. We
then include velocity bias, and show that new contributions appear, a dipole
field being the signature at second order. We test these predictions by
studying the dependence of halo overdensities in cells of fixed matter density:
measurements in simulations show that departures from the mean bias relation
are strongly correlated with the non-local gravitationally induced fields
identified by our formalism. The effects on non-local bias seen in the
simulations are most important for the most biased halos, as expected from our
predictions. The non-locality seen in the simulations is not fully captured by
assuming local bias in Lagrangian space. Accounting for these effects when
modeling galaxy bias is essential for correctly describing the dependence on
triangle shape of the galaxy bispectrum, and hence constraining cosmological
parameters and primordial non-Gaussianity. We show that using our formalism we
remove an important systematic in the determination of bias parameters from the
galaxy bispectrum, particularly for luminous galaxies. (abridged)Comment: 26 pages, 9 figures. v2: improved appendix
Nonlinear Gravitational Clustering: dreams of a paradigm
We discuss the late time evolution of the gravitational clustering in an
expanding universe, based on the nonlinear scaling relations (NSR) which
connect the nonlinear and linear two point correlation functions. The existence
of critical indices for the NSR suggests that the evolution may proceed towards
a universal profile which does not change its shape at late times. We begin by
clarifying the relation between the density profiles of the individual halo and
the slope of the correlation function and discuss the conditions under which
the slopes of the correlation function at the extreme nonlinear end can be
independent of the initial power spectrum. If the evolution should lead to a
profile which preserves the shape at late times, then the correlation function
should grow as [in a universe] een at nonlinear scales. We
prove that such exact solutions do not exist; however, ther e exists a class of
solutions (``psuedo-linear profiles'', PLP's for short) which evolve as
to a good approximation. It turns out that the PLP's are the correlation
functions which arise if the individual halos are assumed to be isothermal
spheres. They are also configurations of mass in which the nonlinear effects of
gravitational clustering is a minimum and hence can act as building blocks of
the nonlinear universe. We discuss the implicatios of this result.Comment: 32 Pages, Submitted to Ap
Stochastic Biasing and Weakly Non-linear Evolution of Power Spectrum
Distribution of galaxies may be a biased tracer of the dark matter
distribution and the relation between the galaxies and the total mass may be
stochastic, non-linear and time-dependent. Since many observations of galaxy
clustering will be done at high redshift, the time evolution of non-linear
stochastic biasing would play a crucial role for the data analysis of the
future sky surveys. In this paper, we develop the weakly non-linear analysis
and attempt to clarify the non-linear feature of the stochastic biasing. We
compute the one-loop correction of the power spectrum for the total mass, the
galaxies and their cross correlation. Assuming the local functional form for
the initial galaxy distribution, we investigate the time evolution of the
biasing parameter and the correlation coefficient. On large scales, we first
find that the time evolution of the biasing parameter could deviate from the
linear prediction in presence of the initial skewness. However, the deviation
can be reduced when the initial stochasticity exists. Next, we focus on the
quasi-linear scales, where the non-linear growth of the total mass becomes
important. It is recognized that the scale-dependence of the biasing
dynamically appears and the initial stochasticity could affect the time
evolution of the scale-dependence. The result is compared with the recent
N-body simulation that the scale-dependence of the halo biasing can appear on
relatively large scales and the biasing parameter takes the lower value on
smaller scales. Qualitatively, our weakly non-linear results can explain this
trend if the halo-mass biasing relation has the large scatter at high redshift.Comment: 29pages, 7 postscript figures, submitted to Ap
MCG+00-32-16: An Irregular Galaxy Close to the Lowest Redshift Absorber on the 3C 273 Line of Sight
MCG+00-32-16 is the galaxy closest in position-velocity space to the lowest
redshift Ly absorber along the line-of-sight to the quasar 3C 273. Its
projected separation is 204 (d/19 Mpc) kpc, where d is the distance from the
Milky Way to the galaxy, and the redshift difference is only 94 km/s; HI
1225+01 is slightly closer in projected separation to the absorber, but has a
greater redshift difference. We present HI synthesis array mapping and CCD
photometry in B and R for MCG+00-32-16. The HI disk is rotating in such a way
that the side of the galaxy closer to the sight-line to the quasar has the
larger velocity difference from the absorber. The absorber may be a ``failed
dwarf'' member of a poor galaxy group of which MCG+00-32-16 and HI 1225+01 are
the only members to have formed stars.Comment: 14 pages, 9 figures, accepted by Astrophysical Journa
The Subaru/XMM-Newton Deep Survey (SXDS) -VII. Clustering Segregation with Ultraviolet and Optical Luminosities of Lyman-Break Galaxies at z~3
We investigate clustering properties of Lyman-break galaxies (LBGs) at z~3
based on deep multi-waveband imaging data from optical to near-infrared
wavelengths in the Subaru/XMM-Newton Deep Field. The LBGs are selected by U-V
and V-z' colors in one contiguous area of 561 arcmin^2 down to z'=25.5. We
study the dependence of the clustering strength on rest-frame UV and optical
magnitudes, which can be indicators of star formation rate and stellar mass,
respectively. The correlation length is found to be a strong function of both
UV and optical magnitudes with brighter galaxies being more clustered than
faint ones in both cases. Furthermore, the correlation length is dependent on a
combination of UV and optical magnitudes in the sense that galaxies bright in
optical magnitude have large correlation lengths irrespective of UV magnitude,
while galaxies faint in optical magnitude have correlation lengths decreasing
with decreasing UV brightness. These results suggest that galaxies with large
stellar masses always belong to massive halos in which they can have various
star formation rates, while galaxies with small stellar masses reside in less
massive halos only if they have low star formation rates. There appears to be
an upper limit to the stellar mass and the star formation rate which is
determined by the mass of hosting dark halos.Comment: 16 pages, 15 figures, accepted for publication in Ap
- …