24,494 research outputs found
The CKM matrix from anti-SU(7) unification of GUT families
We estimate the CKM matrix elements in the recently proposed minimal model,
anti-SU(7) GUT for the family unification,
+\,(singlets). It is shown that the real
angles of the right-handed unitary matrix diagonalizing the mass matrix can be
determined to fit the Particle Data Group data. However, the phase in the
right-handed unitary matrix is not constrained very much. We also includes an
argument about allocating the Jarlskog phase in the CKM matrix.
Phenomenologically, there are three classes of possible parametrizations,
\delq=\alpha,\beta, or of the unitarity triangle. For the choice of
\delq=\alpha, the phase is close to a maximal one.Comment: 11 pages of LaTex file with 2 figure
An experimental study of coupling between combustor pressure, fuel/air mixing, and the flame
Fuel-air mixing behavior under the influence of imposed acoustic oscillations has been studied by investigating the response of the fuel mixture fraction field. The distribution of local fuel mixture fraction inside the mixing zone, which is expected to evolve into the local equivalence ratio in the flame zone, is closely coupled to unstable and oscillatory flame behavior. The Experiment was performed with an aerodynamically-stabilized non-premixed burner. In this study, acoustic oscillations were imposed at 22, 27, 32, 37, and 55Hz. Phase-resolved acetone PLIF was used to image the flow field of both isothermal and reacting flow cases and this data along with the derived quantities of temporal and spatial unmixedness were employed for analysis. The behavior of the unmixedness factor is compared with the previous measurements of oscillations in the flame zone. This comparison shows that local oscillations (of order millimeters or smaller) in fuel/air mixing are closely related to the oscillatory behavior of the flame. For each driving frequency, the mixture fraction oscillates at that frequency but with a slight phase difference between it and the pressure field/flame intensity, indicating that the fuel mixture fraction oscillation are likely the major reason for oscillatory behaviors of this category of flames and combustor geometry
Galaxy Bias and Halo-Occupation Numbers from Large-Scale Clustering
We show that current surveys have at least as much signal to noise in
higher-order statistics as in the power spectrum at weakly nonlinear scales. We
discuss how one can use this information to determine the mean of the galaxy
halo occupation distribution (HOD) using only large-scale information, through
galaxy bias parameters determined from the galaxy bispectrum and trispectrum.
After introducing an averaged, reasonably fast to evaluate, trispectrum
estimator, we show that the expected errors on linear and quadratic bias
parameters can be reduced by at least 20-40%. Also, the inclusion of the
trispectrum information, which is sensitive to "three-dimensionality" of
structures, helps significantly in constraining the mass dependence of the HOD
mean. Our approach depends only on adequate modeling of the abundance and
large-scale clustering of halos and thus is independent of details of how
galaxies are distributed within halos. This provides a consistency check on the
traditional approach of using two-point statistics down to small scales, which
necessarily makes more assumptions. We present a detailed forecast of how well
our approach can be carried out in the case of the SDSS.Comment: 16 pages, 9 figure
Fast radio bursts and their gamma-ray or radio afterglows as Kerr-Newman black hole binaries
Fast radio bursts (FRBs) are radio transients lasting only about a few
milliseconds. They seem to occur at cosmological distances. We propose that
these events can be originated in the collapse of the magnetosphere of
Kerr-Newman black holes (KNBHs). We show that the closed orbits of charged
particles in the magnetosphere of these objects are unstable. After examining
the dependencies on the specific charge of the particle and the spin and charge
of the KNBH, we conclude that the resulting timescale and radiation mechanism
fit well with the extant observations of FRBs. Furthermore, we argue that the
merger of a KNBH binary is one of the plausible central engines for potential
gamma-ray or radio afterglow following a certain FRBs, and can also account for
gravitational wave (GW) events like GW 150914. Our model leads to predictions
that can be tested by combined multi-wavelength electromagnetic and GW
observations.Comment: 6 pages, 4 figures, accepted for publication in Ap
Power Spectrum Analysis of the 2dF QSO Sample Revisited
We revisit the power spectrum analysis of the complete sample of the two
degree field (2dF) QSO redshift (2QZ) survey, as a complementary test of the
work by Outram et al. (2003). A power spectrum consistent with that of the 2QZ
group is obtained. Differently from their approach, fitting of the power
spectrum is investigated incorporating the nonlinear effects, the geometric
distortion and the light-cone effect. It is shown that the QSO power spectrum
is consistent with the cold dark matter (CDM) model with the matter
density parameter . Our constraint on the density
parameter is rather weaker than that of the 2QZ group. We also show that the
constraint slightly depends on the equation of state parameter of the dark
energy. The constraint on from the QSO power spectrum is demonstrated,
though it is not very tight.Comment: 15 pages, 5 figures, accepted for publication in the Astrophysical
Journa
Nearby Gas-Rich Low Surface Brightness Galaxies
We examine the Fisher-Tully cz<1000 km/s galaxy sample to determine whether
it is a complete and representative sample of all galaxy types, including low
surface brightness populations, as has been recently claimed. We find that the
sample is progressively more incomplete for galaxies with (1) smaller physical
diameters at a fixed isophote and (2) lower HI masses. This is likely to lead
to a significant undercounting of nearby gas-rich low surface brightness
galaxies. However, through comparisons to other samples we can understand how
the nearby galaxy counts need to be corrected, and we see some indications of
environmental effects that probably result from the local high density of
galaxies.Comment: 12 page, 2 figures, to appear in Ap
Deriving the Nonlinear Cosmological Power Spectrum and Bispectrum from Analytic Dark Matter Halo Profiles and Mass Functions
We present an analytic model for the fully nonlinear power spectrum P and
bispectrum Q of the cosmological mass density field. The model is based on
physical properties of dark matter halos, with the three main model inputs
being analytic halo density profiles, halo mass functions, and halo-halo
spatial correlations, each of which has been well studied in the literature. We
demonstrate that this new model can reproduce the power spectrum and bispectrum
computed from cosmological simulations of both an n=-2 scale-free model and a
low-density cold dark matter model. To enhance the dynamic range of these large
simulations, we use the synthetic halo replacement technique of Ma & Fry
(2000a), where the original halos with numerically softened cores are replaced
by synthetic halos of realistic density profiles. At high wavenumbers, our
model predicts a slope for the nonlinear power spectrum different from the
often-used fitting formulas in the literature based on the stable clustering
assumption. Our model also predicts a three-point amplitude Q that is scale
dependent, in contrast to the popular hierarchical clustering assumption. This
model provides a rapid way to compute the mass power spectrum and bispectrum
over all length scales where the input halo properties are valid. It also
provides a physical interpretation of the clustering properties of matter in
the universe.Comment: Final version to appear in the Astrophysical Journal 544 (2000).
Minor revisions; 1 additional figure. 25 pages with 6 inserted figure
Effective unidirectional pumping for steady-state amplification without inversion
We discuss an opportunity to achieve amplification without inversion in
three-level cascade scheme using an effective unidirectional pumping via
bidirectional incoherent pump. Analytical solution to the population and the
coherence are obtained in the steady-state regime. With a proper choice of the
parameters, obtained here, the possibility for amplification without inversion
is presented.Comment: 8 Pages, 7 figure
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