8,113 research outputs found
Study of Monte Carlo approach to experimental uncertainty propagation with MSTW 2008 PDFs
We investigate the Monte Carlo approach to propagation of experimental
uncertainties within the context of the established "MSTW 2008" global analysis
of parton distribution functions (PDFs) of the proton at next-to-leading order
in the strong coupling. We show that the Monte Carlo approach using replicas of
the original data gives PDF uncertainties in good agreement with the usual
Hessian approach using the standard Delta(chi^2) = 1 criterion, then we explore
potential parameterisation bias by increasing the number of free parameters,
concluding that any parameterisation bias is likely to be small, with the
exception of the valence-quark distributions at low momentum fractions x. We
motivate the need for a larger tolerance, Delta(chi^2) > 1, by making fits to
restricted data sets and idealised consistent or inconsistent pseudodata.
Instead of using data replicas, we alternatively produce PDF sets randomly
distributed according to the covariance matrix of fit parameters including
appropriate tolerance values, then we demonstrate a simpler method to produce
an arbitrary number of random predictions on-the-fly from the existing
eigenvector PDF sets. Finally, as a simple example application, we use Bayesian
reweighting to study the effect of recent LHC data on the lepton charge
asymmetry from W boson decays.Comment: 37 pages, 17 figures. v2: version published in JHEP. Supplementary
material at http://mstwpdf.hepforge.org/random
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
On the structure of line-driven winds near black holes
A general physical mechanism of the formation of line-driven winds at the
vicinity of strong gravitational field sources is investigated in the frame of
General Relativity. We argue that gravitational redshifting should be taken
into account to model such outflows. The generalization of the Sobolev
approximation in the frame of General Relativity is presented. We consider all
processes in the metric of a nonrotating (Schwarzschild) black hole. The
radiation force that is due to absorbtion of the radiation flux in lines is
derived. It is demonstrated that if gravitational redshifting is taken into
account, the radiation force becomes a function of the local velocity gradient
(as in the standard line-driven wind theory) and the gradient of . We
derive a general relativistic equation of motion describing such flow. A
solution of the equation of motion is obtained and confronted with that
obtained from the Castor, Abbott & Klein (CAK) theory. It is shown that the
proposed mechanism could have an important contribution to the formation of
line-driven outflows from compact objects.Comment: 20 pages, submitted to Ap
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
Head-on infall of two compact objects: Third post-Newtonian Energy Flux
Head-on infall of two compact objects with arbitrary mass ratio is
investigated using the multipolar post-Minkowskian approximation method. At the
third post-Newtonian order the energy flux, in addition to the instantaneous
contributions, also includes hereditary contributions consisting of the
gravitational-wave tails, tails-of-tails and the tail-squared terms. The
results are given both for infall from infinity and also for infall from a
finite distance. These analytical expressions should be useful for the
comparison with the high accuracy numerical relativity results within the limit
in which post-Newtonian approximations are valid.Comment: 25 pages, 2 figures, This version includes the changes appearing in
the Erratum published in Phys. Rev.
Federalism of the Highest Caliber: Counteractive Legislation and the Idaho Firearms Freedom Act
Counteractive legislation is a phenomenon that has been prevalent throughout almost the entirety of U.S. history. The Idaho Firearms Freedom Act, passed in 2010, provides a unique opportunity to survey one piece of counteractive legislation from start to finish. The continued presence of this law in Idaho has the potential to result in detrimental reliance by citizens who believe they are lawfully exercising their right to bear arms, despite being in violation of federal law. This comment provides a close look at the Idaho Firearms Freedom Act and examines the history of counteractive legislation in Idaho and at the national level, as well as its potential side effects
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