28,316 research outputs found
Systematic Errors in Future Weak Lensing Surveys: Requirements and Prospects for Self-Calibration
We study the impact of systematic errors on planned weak lensing surveys and
compute the requirements on their contributions so that they are not a dominant
source of the cosmological parameter error budget. The generic types of error
we consider are multiplicative and additive errors in measurements of shear, as
well as photometric redshift errors. In general, more powerful surveys have
stronger systematic requirements. For example, for a SNAP-type survey the
multiplicative error in shear needs to be smaller than 1%(fsky/0.025)^{-1/2} of
the mean shear in any given redshift bin, while the centroids of photometric
redshift bins need to be known to better than 0.003(fsky/0.025)^{-1/2}. With
about a factor of two degradation in cosmological parameter errors, future
surveys can enter a self-calibration regime, where the mean systematic biases
are self-consistently determined from the survey and only higher-order moments
of the systematics contribute. Interestingly, once the power spectrum
measurements are combined with the bispectrum, the self-calibration regime in
the variation of the equation of state of dark energy w_a is attained with only
a 20-30% error degradation.Comment: 20 pages, 9 figures, to be submitted to MNRAS. Comments are welcom
Band Structure of the Fractional Quantum Hall Effect
The eigenstates of interacting electrons in the fractional quantum Hall phase
typically form fairly well defined bands in the energy space. We show that the
composite fermion theory gives insight into the origin of these bands and
provides an accurate and complete microscopic description of the strongly
correlated many-body states in the low-energy bands. Thus, somewhat like in
Landau's fermi liquid theory, there is a one-to-one correspondence between the
low energy Hilbert space of strongly interacting electrons in the fractinal
quantum Hall regime and that of weakly interacting electrons in the integer
quantum Hall regime.Comment: 10 page
Persistence in the Zero-Temperature Dynamics of the Diluted Ising Ferromagnet in Two Dimensions
The non-equilibrium dynamics of the strongly diluted random-bond Ising model
in two-dimensions (2d) is investigated numerically.
The persistence probability, P(t), of spins which do not flip by time t is
found to decay to a non-zero, dilution-dependent, value . We find
that decays exponentially to zero at large times.
Furthermore, the fraction of spins which never flip is a monotonically
increasing function over the range of bond-dilution considered. Our findings,
which are consistent with a recent result of Newman and Stein, suggest that
persistence in disordered and pure systems falls into different classes.
Furthermore, its behaviour would also appear to depend crucially on the
strength of the dilution present.Comment: some minor changes to the text, one additional referenc
Brownian dynamics simulations of planar mixed flows of polymer solutions at finite concentrations
Periodic boundary conditions for planar mixed flows are implemented in the
context of a multi-chain Brownian dynamics simulation algorithm. The effect of
shear rate , and extension rate , on the size of
polymer chains, \left, and on the polymer contribution to
viscosity, , is examined for solutions of FENE dumbbells at finite
concentrations, with excluded volume interactions between the beads taken into
account. The influence of the mixedness parameter, , and flow strength,
, on \left and , is also examined, where
corresponds to pure shear flow, and
corresponds to pure extensional flow. It is shown that there exists a critical
value, , such that the flow is shear dominated for , and extension dominated for .Comment: 18 pages, 12 figures, to appear in Chemical Engineering Scienc
Cross-correlation Tomography: Measuring Dark Energy Evolution with Weak Lensing
A cross-correlation technique of lensing tomography is presented to measure
the evolution of dark energy in the universe. The variation of the weak lensing
shear with redshift around massive foreground objects like bright galaxies and
clusters depends solely on ratios of angular diameter distances. Use of the
massive foreground halos allow us to compare relatively high, linear shear
values in the same part of the sky, thus largely eliminating the dominant
source of systematic error in cosmological weak lensing measurements. The
statistic we use does not rely on knowledge of the foreground mass distribution
and is only shot-noise limited. We estimate the constraints that deep lensing
surveys with photometric redshifts can provide on the dark energy density
Omega, the equation of state parameter w and its redshift derivative w'. The
accuracies on w and w' are: sigma(w) ~ 0.02 fsky^{-1/2} and sigma(w') ~ 0.05
fsky^{-1/2}, where fsky is the fraction of sky covered by the survey and
sigma(Omega)=0.03 is assumed in the marginalization. Combining our
cross-correlation method with standard lensing tomography, which has
complementary degeneracies, will allow measurement of the dark energy
parameters with significantly better accuracy.Comment: 5 pages, 2 figures, submitted to PRL. Error in shear signal corrected
- parameter constraints about a factor of 2 wors
Composite fermions in a long-range random magnetic field: Quantum Hall effect versus Shubnikov-de Haas oscillations
We study transport in a smooth random magnetic field, with emphasis on
composite fermions (CF) near half-filling of the Landau level. When either the
amplitude of the magnetic field fluctuations or its mean value is
large enough, the transport is of percolating nature. While at the
percolation effects enhance the conductivity , increasing
(which corresponds to moving away from half-filling for the CF problem) leads
to a sharp falloff of and, consequently, to the quantum
localization of CFs. We demonstrate that the localization is a crucial factor
in the interplay between the Shubnikov-de Haas and quantum Hall oscillations,
and point out that the latter are dominant in the CF metal.Comment: 4 pages, RevTe
Gravitational Lensing Bound On The Average Redshift Of Gamma Ray Bursts In Models With Evolving Lenses
Identification of gravitationally lensed Gamma Ray Bursts (GRBs) in the BATSE
4B catalog can be used to constrain the average redshift of the GRBs.
In this paper we investigate the effect of evolving lenses on the of
GRBs in different cosmological models of universe. The cosmological parameters
$\Omega$ and $\Lambda$ have an effect on the of GRBs. The other factor
which can change the of GRBs is higher in evolving model of galaxies as compared to
non-evolving models of galaxies.Comment: 23 pages,one plain LaTeX file with three postscript figures This is
modified version with recent BATSE efficiency parameter and with the latest F
paramete
Supplementation of nitrogen and its influence on free sugars, amino acid and protein metabolism in roots and internodes of wheat
Effect of different doses of nitrogen (N) (90, 120, 150 and 180 kg Nha–1) on the activities of aminotransferases and alkaline inorganic pyrophosphatase (AIP) in relation to the accumulation of proteins, amino acids and sugars in roots and internodes at 15 and 40 days post anthesis (DPA) stages was studied in six wheat genotypes namely HD 2967, GLU 1101, PBW 343, BW 9022, PH-132-4840 and PBW 550. Supra-optimal N doses (150 kg Nha–1 and 180 kg Nha–1) accentuated glutamate oxaloacetate transaminase (GOT), glutamate pyruvate transaminase (GPT) and alkaline inorganic pyrophosphatase activities in correspondence with an increase in amino acid, protein and sugar content in both roots and internodes in all the six genotypes. Activities of analyzed enzymes were significantly high at 15 days post anthesis (DPA) stage and thereafter declined at maturity (40 DPA) in parallel with decrease in amino acid contents. Maximum activity of GOT, GPT and AIP was observed in HD 2967 and GLU 1101 genotypes along with higher build up of proteins and amino acids which resulted in higher grain yield. Activity of GPT was comparatively high over GOT, indicating its major role towards protein synthesis. Grain filling processes in terms of proteins and amino acids were positively correlated with GOT and GPT activities while sugars were correlated to AIP. Thus, nitrogen acquisition and assimilation resulted in favoured utilization of N in form of amino acid and proteins accumulation while sugar content was also stimulated. Due to immense activities of aminotransferases and higher contents of amino acids and proteins in GLU 1101 and HD 2967 genotypes at optimal dose and higher dose of N, these genotypes hold future potential for developing new cultivars with better grain quality characteristics
Persistence in the zero-temperature dynamics of the -states Potts model on undirected-directed Barab\'asi-Albert networks and Erd\"os-R\'enyi random graphs
The zero-temperature Glauber dynamics is used to investigate the persistence
probability in the Potts model with , ,..., states on {\it directed} and {\it
undirected} Barab\'asi-Albert networks and Erd\"os-R\'enyi random graphs. In
this model it is found that decays exponentially to zero in short times
for {\it directed} and {\it undirected} Erd\"os-R\'enyi random graphs. For {\it
directed} and {\it undirected} Barab\'asi-Albert networks, in contrast it
decays exponentially to a constant value for long times, i.e, is
different from zero for all values (here studied) from ; this shows "blocking" for all these values. Except that for
in the {\it undirected} case tends exponentially to zero;
this could be just a finite-size effect since in the other "blocking" cases you
may have only a few unchanged spins.Comment: 14 pages, 8 figures for IJM
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