2,790 research outputs found
Expected Precision of Higgs Boson Partial Widths within the Standard Model
We discuss the sources of uncertainty in calculations of the partial widths
of the Higgs boson within the Standard Model. The uncertainties come from two
sources: the truncation of perturbation theory and the uncertainties in input
parameters. We review the current status of perturbative calculations and note
that these are already reaching the parts-per-mil level of accuracy for the
major decay modes. The main sources of uncertainty will then come from the
parametric dependences on alpha_s, m_b, and m_c. Knowledge of these parameters
is systematically improvable through lattice gauge theory calculations. We
estimate the precision that lattice QCD will achieve in the next decade and the
corresponding precision of the Standard Model predictions for Higgs boson
partial widths.Comment: 20 pages, 1 figure; v2: minor typo correction
Shakedown and limit analysis of 90° pipe bends under internal pressure, cyclic in-plane bending and cyclic thermal loading
The Linear Matching Method is used to create the shakedown limit and limit load interaction curves of 90 degree pipe bends for a range of bend factors. Two load cases are considered i) internal pressure and inplane bending (which includes opening, closing and reversed bending) and ii) internal pressure and a cyclic through wall temperature difference giving rise to thermal stresses. The effects of the ratios of bend radius to pipe mean radius (R/r) and mean radius to wall thickness (r/t) on the limit load and shakedown behaviour are presented
The Running Coupling from SU(3) Gauge Theory
We present high precision results on the static quark-antiquark-potential on
32^4 and smaller lattices, using the standard Wilson action at BETA = 6.0, 6.2,
6.4, and 6.8 on the Connection Machine CM-2. Within our statistical errors (1%)
we did not observe any finite size effects affecting the potential values, on
varying the spatial lattice extent from 0.9 fm up to 3.3 fm. We find violations
of asymptotic scaling in the bare coupling up to BETA = 6.8. We demonstrate
that scaling violations on the string tension can be considerably reduced by
introducing effective coupling schemes, which allow for a safer extrapolation
of LAMBDA_Lattice to its continuum value. We are also able to see and to
quantify the running of the coupling from the interquark force. From this we
extract the ratio \sqrt{SIGMA}/LAMBDA_L. Both methods yield consistent values
for the LAMBDA-parameter: LAMBDA_MSbar = 0.558(-0.007+0.017)\sqrt{SIGMA}
= 246(-3+7) MeV.Comment: (Talk G. Bali at Lattice 92, Amsterdam), 4 Pages, 4 Postscript
figures, LaTeX with espcrc2, and epsf style file
A direct method for the evaluation of lower and upper bound ratchet limits
The calculation of the ratchet limit is often vital for the assessment of the design and integrity of components which are subject to cyclic loading. This work describes the addition of a lower bound calculation to the existing Linear Matching Method upper bound ratchet analysis method. This lower bound calculation is based on Melan's theorem, and makes use of the residual and elastic stress fields calculated by the upper bound technique to calculate the lower bound ratchet limit multiplier. By doing this, the method combines the stable convergence of the upper bound method but retains the conservatism offered by the lower bound. These advantages are complemented by the ability of the Linear Matching Method to consider real 3D geometries subject to complex load histories including the effect of temperature dependent yield stress. The convergence properties of this lower bound ratchet limit are investigated through a benchmark problem of a plate with a central hole subject to cyclic thermal and mechanical loads. To demonstrate the effectiveness of the method, the ratchet limit of a thick walled pipe intersection, also subject to cyclic thermal and mechanical loads, is considered. Validation of these results is provided by full elastic-plastic FEA in Abaqus
Comparing tests of autoregressive versus moving average errors in regression models using Bahadur's asymptotic relative efficiency
The purpose of this paper is to use Bahadur's asymptotic relative efficiency measure to compare the performance of various tests of autoregressive (AR) versus moving average (MA) error processes in regression models. Tests to be examined include non-nested procedures of the models against each other, and classical procedures based upon testing both the AR and MA error processes against the more general autoregressive-moving average model
A Bayesian-Influence Model for Error Probability Analysis of Combine Operations in Harvesting
Harvesting is one of the most important agricultural operations because it captures the value from the entire cropping season. In modern agriculture, grain harvesting has been mechanized through the combine harvester. A combine harvester enables highly productive crop harvesting. Combine harvesting performance depends on the highly variable skill of combine operators and associated operator error. An approach was developed to analyze the risk of the combine harvesting operation as it relates to operator error. Specifically, a risk analysis model was built based on a task analysis from operator interviews and estimates of the probability of operator error. This paper employs a Bayesian approach to assess risks in combine operation. This approach applies a Bayesian Belief Network to agriculture operations, which represents a new application for this risk analysis tool. Sensitivity analysis of different errors and operator skill levels was also performed. The preliminary results indicate that a reduction of human operator action errors can substantially improve the outcomes of the human-machine interaction
Nematic Fermi Fluids in Condensed Matter Physics
Correlated electron fluids can exhibit a startling array of complex phases,
among which one of the more surprising is the electron nematic, a
translationally invariant metallic phase with a spontaneously generated spatial
anisotropy. Classical nematics generally occur in liquids of rod-like
molecules; given that electrons are point-like, the initial theoretical
motivation for contemplating electron nematics came from thinking of the
electron fluid as a quantum melted electron crystal, rather than a strongly
interacting descendent of a Fermi gas. That such phases exist in nature was
established by dramatic transport experiments in ultra-clean quantum Hall
systems in 1999 and in Sr3Ru2O7 in a strong magnetic field in 2007.
In this paper, we briefly review the theoretical considerations governing
nematic order, summarize the quantum Hall and Sr3Ru2O7 experiments that
unambiguously establish the existence of this phase, and survey some of the
current evidence for such a phase in the cuprate and Fe-based high temperature
superconductors.Comment: 30 pages, 7 figures (some in color); to appear in Annual Reviews of
Condensed Matter Physics. Edited version
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