2,473 research outputs found
Non-gaussian CMB temperature fluctuations from peculiar velocities of clusters
We use numerical simulations of a (480 Mpc/h)^3 volume to show that the
distribution of peak heights in maps of the temperature fluctuations from the
kinematic and thermal Sunyaev-Zeldovich effects will be highly non-Gaussian,
and very different from the peak height distribution of a Gaussian random
field. We then show that it is a good approximation to assume that each peak in
either SZ effect is associated with one and only one dark matter halo. This
allows us to use our knowledge of the properties of haloes to estimate the peak
height distributions. At fixed optical depth, the distribution of peak heights
due to the kinematic effect is Gaussian, with a width which is approximately
proportional to optical depth; the non-Gaussianity comes from summing over a
range of optical depths. The optical depth is an increasing function of halo
mass, and the distribution of halo speeds is Gaussian, with a dispersion which
is approximately independent of halo mass. This means that observations of the
kinematic effect can be used to put constraints on how the abundance of massive
clusters evolves, and on the evolution of cluster velocities. The
non-Gaussianity of the thermal effect, on the other hand, comes primarily from
the fact that, on average, the effect is larger in more massive haloes, and the
distribution of halo masses is highly non-Gaussian. We also show that because
haloes of the same mass may have a range of density and velocity dispersion
profiles, the relation between halo mass and the amplitude of the thermal
effect is not deterministic, but has some scatter.Comment: Revised, citation added. To appear in MNRA
Spectral Continuity in Dense QCD
The vector mesons in three-flavor quark matter with chiral and diquark
condensates are studied using the in-medium QCD sum rules. The diquark
condensate leads to a mass splitting between the flavor-octet and
flavor-singlet channels. At high density, the singlet vector meson disappears
from the low-energy spectrum, while the octet vector mesons survive as light
excitations with a mass comparable to the fermion gap. A possible connection
between the light gluonic modes and the flavor-octet vector mesons at high
density is also discussed.Comment: 4 pages, 3 figures; version to appear in Phys. Rev.
Non-Gaussianity analysis of GW background made by short-duration burst signals
We study an observational method to analyze non-Gaussianity of a
gravitational wave (GW) background made by superposition of weak burst signals.
The proposed method is based on fourth-order correlations of data from four
detectors, and might be useful to discriminate the origin of a GW background.
With a formulation newly developed to discuss geometrical aspects of the
correlations, it is found that the method provides us with linear combinations
of two interesting parameters, I_2 and V_2 defined by the Stokes parameters of
individual GW burst signals. We also evaluate sensitivities of specific
detector networks to these parameters.Comment: 18 pages, to appear in PR
Physical Properties of UDF12 Galaxies in Cosmological simulations
We have performed a large cosmological hydrodynamics simulation tailored to
the deep survey with the Hubble Space Telescope made in 2012, the so-called
UDF12 campaign. After making a light-cone output, we have applied the same
color selection criteria as the UDF12 campaign to select galaxies from our
simulation, and then, have examined the physical properties of them as a proxy
of the real observed UDF12 galaxies at . As a result, we find that the
halo mass is almost linearly proportional to the observed ultraviolet (UV)
luminosity ( at ). The dust
attenuation and UV slope well correlates with the observed UV
luminosity, which is consistent with observations quantitatively. The star
formation rate (SFR) is also linearly proportional to the stellar mass and the
specific SFR shows only a weak dependency on the mass. We also find an
increasing star formation history with a time-scale of Myr in the
high- galaxies. An average metallicity weighted by the Lyman continuum
luminosity reaches up to Solar even at , suggesting a rapid
metal enrichment. We also expect mJy at 350 GHz of the dust thermal
emission from the galaxies with , which can be detectable with
the Atacama Large Milimetre-submilimetre Array. The galaxies selected by the
UDF12 survey contribute to only of the cosmic SFR density from to , respectively. The James Webb Space Telescope will push
the detection fraction up to .Comment: re-Submitted to MNRAS; 16 pages; 14 figures; 1 tables
Prospects for direct detection of circular polarization of gravitational-wave background
We discussed prospects for directly detecting circular polarization signal of
gravitational wave background. We found it is generally difficult to probe the
monopole mode of the signal due to broad directivity of gravitational wave
detectors. But the dipole (l=1) and octupole (l=3) modes of the signal can be
measured in a simple manner by combining outputs of two unaligned detectors,
and we can dig them deeply under confusion and detector noises. Around f~0.1mHz
LISA will provide ideal data streams to detect these anisotropic components
whose magnitudes are as small as ~1 percent of the detector noise level in
terms of the non-dimensional energy density \Omega_{GW}(f).Comment: 5 pages, 1 figure, PRL in pres
New Critical Point Induced by the Axial Anomaly in Dense QCD
We study the interplay between chiral and diquark condensates within the
framework of the Ginzburg-Landau free energy, and classify possible phase
structures of two and three-flavor massless QCD. The QCD axial anomaly acts as
an external field applied to the chiral condensate in a color superconductor
and leads to a crossover between the broken chiral symmetry and the color
superconducting phase, and, in particular, to a new critical point in the QCD
phase diagram.Comment: 4 pages, 4 figures included, version to appear in Phys. Rev. Let
Reply to Comment on "Quantum Phase Transition of Randomly-Diluted Heisenberg Antiferromagnet on a Square Lattice"
This is a reply to the comment by A. W. Sandvik (cond-mat/0010433) on our
paper Phys. Rev. Lett. 84, 4204 (2000). We show that his data do not conflict
with our data nor with our conclusions.Comment: RevTeX, 1 page; Revised versio
Strong-coupling expansion for the momentum distribution of the Bose Hubbard model with benchmarking against exact numerical results
A strong-coupling expansion for the Green's functions, self-energies and
correlation functions of the Bose Hubbard model is developed. We illustrate the
general formalism, which includes all possible inhomogeneous effects in the
formalism, such as disorder, or a trap potential, as well as effects of thermal
excitations. The expansion is then employed to calculate the momentum
distribution of the bosons in the Mott phase for an infinite homogeneous
periodic system at zero temperature through third-order in the hopping. By
using scaling theory for the critical behavior at zero momentum and at the
critical value of the hopping for the Mott insulator to superfluid transition
along with a generalization of the RPA-like form for the momentum distribution,
we are able to extrapolate the series to infinite order and produce very
accurate quantitative results for the momentum distribution in a simple
functional form for one, two, and three dimensions; the accuracy is better in
higher dimensions and is on the order of a few percent relative error
everywhere except close to the critical value of the hopping divided by the
on-site repulsion. In addition, we find simple phenomenological expressions for
the Mott phase lobes in two and three dimensions which are much more accurate
than the truncated strong-coupling expansions and any other analytic
approximation we are aware of. The strong-coupling expansions and scaling
theory results are benchmarked against numerically exact QMC simulations in two
and three dimensions and against DMRG calculations in one dimension. These
analytic expressions will be useful for quick comparison of experimental
results to theory and in many cases can bypass the need for expensive numerical
simulations.Comment: 48 pages 14 figures RevTe
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