11,393 research outputs found
Halo Mass Profiles and Low Surface Brightness Galaxies Rotation Curves
A recent study has claimed that the rotation curve shapes and mass densities
of Low Surface Brightness (LSB) galaxies are largely consistent with
CDM predictions, in contrast to a large body of observational work. I
demonstrate that the method used to derive this conclusion is incapable of
distinguishing the characteristic steep CDM mass-density distribution from the
core-dominated mass-density distributions found observationally: even
core-dominated pseudo-isothermal haloes would be inferred to be consistent with
CDM. This method can therefore make no definitive statements on the
(dis)agreement between the data and CDM simulations. After introducing an
additional criterion that does take the slope of the mass-distribution into
account I find that only about a quarter of the LSB galaxies investigated are
possibly consistent with CDM. However, for most of these the fit parameters are
so weakly constrained that this is not a strong conclusion. Only 3 out of 52
galaxies have tightly constrained solutions consistent with CDM. Two
of these galaxies are likely dominated by stars, leaving only one possible dark
matter dominated, CDM-consistent candidate, forming a mere 2 per cent of the
total sample. These conclusions are based on comparison of data and simulations
at identical radii and fits to the entire rotation curves. LSB galaxies that
are consistent with CDM simulations, if they exist, seem to be rare indeed.Comment: Accepted for publication in Astrophysical Journa
Identification of Colour Reconnection using Factorial Correlator
A new signal is proposed for the colour reconnection in the hadronic decay of
W+ W- in e+e- collisions. Using Pythia Monte Carlo it is shown that this
signal, being based on the factorial correlator, is more sensitive than the
ones using only averaged quantities.Comment: 6 pages 1 postscript figur
Corrector theory for MsFEM and HMM in random media
We analyze the random fluctuations of several multi-scale algorithms such as
the multi-scale finite element method (MsFEM) and the finite element
heterogeneous multiscale method (HMM), that have been developed to solve
partial differential equations with highly heterogeneous coefficients. Such
multi-scale algorithms are often shown to correctly capture the homogenization
limit when the highly oscillatory random medium is stationary and ergodic. This
paper is concerned with the random fluctuations of the solution about the
deterministic homogenization limit. We consider the simplified setting of the
one dimensional elliptic equation, where the theory of random fluctuations is
well understood. We develop a fluctuation theory for the multi-scale algorithms
in the presence of random environments with short-range and long-range
correlations. What we find is that the computationally more expensive method
MsFEM captures the random fluctuations both for short-range and long-range
oscillations in the medium. The less expensive method HMM correctly captures
the fluctuations for long-range oscillations and strongly amplifies their size
in media with short-range oscillations. We present a modified scheme with an
intermediate computational cost that captures the random fluctuations in all
cases.Comment: 41 page
Electroweak Beautygenesis: From b {\to} s CP-violation to the Cosmic Baryon Asymmetry
We address the possibility that CP-violation in mixing may
help explain the origin of the cosmic baryon asymmetry. We propose a new
baryogenesis mechanism - "Electroweak Beautygenesis" - explicitly showing that
these two CP-violating phenomena can be sourced by a common CP-phase. As an
illustration, we work in the Two-Higgs-Doublet model. Because the relevant
CP-phase is flavor off-diagonal, this mechanism is less severely constrained by
null results of electric dipole moment searches than other scenarios. We show
how measurements of flavor observables by the D0, CDF, and LHCb collaborations
test this scenario.Comment: 4 pages, 1 figure, 1 tabl
Fate of non-Fermi liquid behavior in QED at finite chemical potential
The damping rate of two-dimensional massless Dirac fermions exhibit non-Fermi
liquid behavior, , due to gauge field at zero
temperature and zero chemical potential. We study the fate of this behavior at
finite chemical potential. We fist calculate explicitly the temporal and
spatial components of vacuum polarization functions. The analytical expressions
imply that the temporal component of gauge field develops a static screening
length at finite chemical potential while the transverse component remains
long-ranged owing to gauge invariance. We then calculate the fermion damping
rate and show that the temporal gauge field leads to normal Fermi liquid
behavior but the transverse gauge field leads to non-Fermi liquid behavior
at zero temperature. This energy-dependence is more
regular than and does not change as chemical potential
varies.Comment: 12 pages, 1 figur
Crop Choice, Non-Target Pest Levels, Yield Loss and Their Effect on Insecticide Use in South Dakota
Agriculturally, South Dakota is a unique state possessing the highest rate of adoption for genetically modified crop varieties. In 2009 ninety-six percent of corn acres planted in South Dakota were genetically modified compared with eighty-five percent nationally (Economic Research Service). Additionally, South Dakota has seen a dramatic increase in the number of acres treated with insecticide over the past 20 years. These two situations taken together seem to be counterintuitive. Some genetically modified varieties, such as Bt corn, are equipped with genetic defenses so that they can protect the plant from target pests. Intuitively, one would expect to see a decrease in insecticide use as adoption of genetically modified varieties increase. Recent studies have found that there is a reduction in herbicides applied to herbicide tolerant varieties. Here in South Dakota, though, producers have expressed the opinion that the increase in insecticide use is the result of the emergence and spread of the soybean aphid in the state. This research seeks to address the underlying causes of the increase in insecticide use.Bt corn, GM crops, insecticide, Agricultural and Food Policy, Crop Production/Industries, Q1, Q2, Q5,
Quantum entropy of the Kerr black hole arising from gravitational perturbation
The quantum entropy of the Kerr black hole arising from gravitational
perturbation is investigated by using Null tetrad and \'t Hooft\'s brick-wall
model. It is shown that effect of the graviton\'s spins on the subleading
correction is dependent of the square of the spins and the angular momentum per
unit mass of the black hole, and contribution of the logarithmic term to the
entropy will be positive, zero, and negative for different value of .Comment: 8 pages, 1 figure, Latex. to appear in Phys. Rev.
Asymptotic tails of massive scalar fields in a stationary axisymmetric EMDA black hole geometry
The late-time tail behavior of massive scalar fields is studied analytically
in a stationary axisymmetric EMDA black hole geometry. It is shown that the
asymptotic behavior of massive perturbations is dominated by the oscillatory
inverse power-law decaying tail at the intermediate
late times, and by the asymptotic tail at asymptotically
late times. Our result seems to suggest that the intermediate tails and the asymptotically tails
may be quite general features for evolution of massive scalar fields in any
four dimensional asymptotically flat rotating black hole backgrounds.Comment: 6 page
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