513 research outputs found
Perspectives on the Missiological Legacy of Martin Luther and the Protestant Reformation
Upon the occasion of the 500th anniversary Martin Luther’s publication of his 95 theses, this composite article brings together five perspectives on the missiological legacy of the reformer and the subsequent Protestant Reformation. The blend of voices makes clear that Luther and the subsequent Protestant Reformation do not have a simple missiological legacy but rather various legacies: theological, ecclesiological, political, and practical; some of which co-exist, and even collide, in the same ecclesiastical community. The scandalous legacy of a splintered and splintering church remains. Yet, demonstrations of mutual recognition, reciprocal respect, and genuine fellowship can be found in certain missiological circles
Shock Breakout in Core-Collapse Supernovae and its Neutrino Signature
(Abridged) We present results from dynamical models of core-collapse
supernovae in one spatial dimension, employing a newly-developed Boltzmann
neutrino radiation transport algorithm, coupled to Lagrangean hydrodynamics and
a consistent high-density nuclear equation of state. We focus on shock breakout
and its neutrino signature and follow the dynamical evolution of the cores of
11 M_sun, 15 M_sun, and 20 M_sun progenitors through collapse and the first 250
milliseconds after bounce. We examine the effects on the emergent neutrino
spectra, light curves, and mix of species of artificial opacity changes, the
number of energy groups, the weak magnetism/recoil corrections, nucleon-nucleon
bremsstrahlung, neutrino-electron scattering, and the compressibility of
nuclear matter. Furthermore, we present the first high-resolution look at the
angular distribution of the neutrino radiation field both in the
semi-transparent regime and at large radii and explore the accuracy with which
our tangent-ray method tracks the free propagation of a pulse of radiation in a
near vacuum. Finally, we fold the emergent neutrino spectra with the
efficiencies and detection processes for a selection of modern underground
neutrino observatories and argue that the prompt electron-neutrino breakout
burst from the next galactic supernova is in principle observable and usefully
diagnostic of fundamental collapse/supernova behavior. Though we are not in
this study focusing on the supernova mechanism per se, our simulations support
the theoretical conclusion (already reached by others) that spherical (1D)
supernovae do not explode when good physics and transport methods are employed.Comment: 16 emulateapj pages, plus 24 postscript figures, accepted to The
Astrophysical Journal; text revised; neutrino oscillation section expanded;
Fig. 22 correcte
Quantitative shadowgraphy and proton radiography for large intensity modulations
Shadowgraphy is a technique widely used to diagnose objects or systems in
various fields in physics and engineering. In shadowgraphy, an optical beam is
deflected by the object and then the intensity modulation is captured on a
screen placed some distance away. However, retrieving quantitative information
from the shadowgrams themselves is a challenging task because of the non-linear
nature of the process. Here, a novel method to retrieve quantitative
information from shadowgrams, based on computational geometry, is presented for
the first time. This process can be applied to proton radiography for electric
and magnetic field diagnosis in high-energy-density plasmas and has been
benchmarked using a toroidal magnetic field as the object, among others. It is
shown that the method can accurately retrieve quantitative parameters with
error bars less than 10%, even when caustics are present. The method is also
shown to be robust enough to process real experimental results with simple pre-
and post-processing techniques. This adds a powerful new tool for research in
various fields in engineering and physics for both techniques
A New Algorithm for Supernova Neutrino Transport and Some Applications
We have developed an implicit, multi-group, time-dependent, spherical
neutrino transport code based on the Feautrier variables, the tangent-ray
method, and accelerated iteration. The code achieves high
angular resolution, is good to O(), is equivalent to a Boltzmann solver
(without gravitational redshifts), and solves the transport equation at all
optical depths with precision. In this paper, we present our formulation of the
relevant numerics and microphysics and explore protoneutron star atmospheres
for snapshot post-bounce models. Our major focus is on spectra, neutrino-matter
heating rates, Eddington factors, angular distributions, and phase-space
occupancies. In addition, we investigate the influence on neutrino spectra and
heating of final-state electron blocking, stimulated absorption, velocity terms
in the transport equation, neutrino-nucleon scattering asymmetry, and weak
magnetism and recoil effects. Furthermore, we compare the emergent spectra and
heating rates obtained using full transport with those obtained using
representative flux-limited transport formulations to gauge their accuracy and
viability. Finally, we derive useful formulae for the neutrino source strength
due to nucleon-nucleon bremsstrahlung and determine bremsstrahlung's influence
on the emergent and neutrino spectra.Comment: 58 pages, single-spaced LaTeX, 23 figures, revised title, also
available at http://jupiter.as.arizona.edu/~burrows/papers, accepted for
publication in the Ap.
The Compact Linear Collider (CLIC) - 2018 Summary Report
The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear e+e- collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years
Partial validation of CFD blast simulation in a cityscape environment featuring structural failure
We demonstrate the capabilities of computational fluid dynamics (CFD) and a pressure-impulse failure model to predict blast loading and structural damage in a geometrically complex cityscape. The simulated loading is compared against experimental results for 69 g PE4 in a 1/50th scale model with wood-framed and plywood-faced buildings; data were collected from 11 pressure gauges throughout. In the initial simulation, geometric features were modeled as perfectly rigid, whereas buildings in the experiment failed: the resulting differences between the model and experiment allowed us to evaluate CFD when failure occurs. Simulated peak pressures during the first positive phase were still within 20% of experiment at most pressure gauges. However, errors in first phase impulses were around 40%, suggesting that building-failure effects are greater toward the phase end. Then, to model building-failure effects, we attempted to fit pressure-impulse failure curves to the plywood-faces: this proved too simplistic to produce realistic blast wave behavior due to the various, complex failure modes. This work illustrates key limitations of available CFD software and the pressure-impulse fail- ure model – both industry-standard tools to determine structural response to blast. We conclude that stronger coupling between blast loading and structural response is needed where significant failure occurs
The International Linear Collider Technical Design Report - Volume 4: Detectors
The International Linear Collider Technical Design Report (TDR) describes in
four volumes the physics case and the design of a 500 GeV centre-of-mass energy
linear electron-positron collider based on superconducting radio-frequency
technology using Niobium cavities as the accelerating structures. The
accelerator can be extended to 1 TeV and also run as a Higgs factory at around
250 GeV and on the Z0 pole. A comprehensive value estimate of the accelerator
is give, together with associated uncertainties. It is shown that no
significant technical issues remain to be solved. Once a site is selected and
the necessary site-dependent engineering is carried out, construction can begin
immediately. The TDR also gives baseline documentation for two high-performance
detectors that can share the ILC luminosity by being moved into and out of the
beam line in a "push-pull" configuration. These detectors, ILD and SiD, are
described in detail. They form the basis for a world-class experimental
programme that promises to increase significantly our understanding of the
fundamental processes that govern the evolution of the Universe.Comment: See also http://www.linearcollider.org/ILC/TDR . The full list of
signatories is inside the Repor
Thermal Infrared MMTAO Observations of the HR 8799 Planetary System
We present direct imaging observations at wavelengths of 3.3, 3.8 (L',band),
and 4.8 (M band) microns, for the planetary system surrounding HR 8799. All
three planets are detected at L'. The c and d component are detected at 3.3
microns, and upper limits are derived from the M band observations. These
observations provide useful constraints on warm giant planet atmospheres. We
discuss the current age constraints on the HR 8799 system, and show that
several potential co-eval objects can be excluded from being co-moving with the
star. Comparison of the photometry is made to models for giant planet
atmospheres. Models which include non-equilibrium chemistry provide a
reasonable match to the colors of c and d. From the observed colors in the
thermal infrared we estimate T_eff < 960 K for b, and T_eff=1300 and 1170 K for
c and d, respectively. This provides an independent check on the effective
temperatures and thus masses of the objects from the Marois 2008 results.Comment: 16 pages, 6 figures, accepted to Ap
Simulation of density measurements in plasma wakefields using photon acceleration
One obstacle in plasma accelerator development is the limitation of techniques to diagnose and measure plasma wakefield parameters. In this paper, we present a novel concept for the density measurement of a plasma wakefield using photon acceleration, supported by extensive particle in cell simulations of a laser pulse that copropagates with a wakefield. The technique can provide the perturbed electron density profile in the laser's reference frame, averaged over the propagation length, to be accurate within 10%. We discuss the limitations that affect the measurement: small frequency changes, photon trapping, laser displacement, stimulated Raman scattering, and laser beam divergence. By considering these processes, one can determine the optimal parameters of the laser pulse and its propagation length. This new technique allows a characterization of the density perturbation within a plasma wakefield accelerator
Quantitative single shot and spatially resolved plasma wakefield diagnostics
Diagnosing plasma conditions can give great advantages in optimizing plasma wakefield accelerator experiments. One possible method is that of photon acceleration. By propagating a laser probe pulse through a plasma wakefield and extracting the imposed frequency modulation, one can obtain an image of the density modulation of the wakefield. In order to diagnose the wakefield parameters at a chosen point in the plasma, the probe pulse crosses the plasma at oblique angles relative to the wakefield. In this paper, mathematical expressions relating the frequency modulation of the laser pulse and the wakefield density profile of the plasma for oblique crossing angles are derived. Multidimensional particle-in-cell simulation results presented in this paper confirm that the frequency modulation profiles and the density modulation profiles agree to within 10%. Limitations to the accuracy of the measurement are discussed in this paper. This technique opens new possibilities to quantitatively diagnose the plasma wakefield density at known positions within the plasma column
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