17,104 research outputs found
Higher Spin BRS Cohomology of Supersymmetric Chiral Matter in D=4
We examine the BRS cohomology of chiral matter in , supersymmetry
to determine a general form of composite superfield operators which can suffer
from supersymmetry anomalies. Composite superfield operators \Y_{(a,b)} are
products of the elementary chiral superfields and \ov S and the
derivative operators D_\a, \ov D_{\dot \b} and \pa_{\a \dot \b}. Such
superfields \Y_{(a,b)} can be chosen to have `' symmetrized undotted
indices \a_i and `' symmetrized dotted indices \dot \b_j. The result
derived here is that each composite superfield \Y_{(a,b)} is subject to
potential supersymmetry anomalies if is an odd number, which means that
\Y_{(a,b)} is a fermionic superfield.Comment: 15 pages, CPT-TAMU-20/9
The Last of the Finite Loop Amplitudes in QCD
We use on-shell recursion relations to determine the one-loop QCD scattering
amplitudes with a massless external quark pair and an arbitrary number (n-2) of
positive-helicity gluons. These amplitudes are the last of the unknown
infrared- and ultraviolet-finite loop amplitudes of QCD. The recursion
relations are similar to ones applied at tree level, but contain new
non-trivial features corresponding to poles present for complex momentum
arguments but absent for real momenta. We present the relations and the compact
solutions to them, valid for all n. We also present compact forms for the
previously-computed one-loop n-gluon amplitudes with a single negative helicity
and the rest positive helicity.Comment: 45 pages, revtex, 7 figures, v2 minor correction
Bootstrapping One-Loop QCD Amplitudes with General Helicities
The recently developed on-shell bootstrap for computing one-loop amplitudes
in non-supersymmetric theories such as QCD combines the unitarity method with
loop-level on-shell recursion. For generic helicity configurations, the
recursion relations may involve undetermined contributions from non-standard
complex singularities or from large values of the shift parameter. Here we
develop a strategy for sidestepping difficulties through use of pairs of
recursion relations. To illustrate the strategy, we present sets of recursion
relations needed for obtaining n-gluon amplitudes in QCD. We give a recursive
solution for the one-loop n-gluon QCD amplitudes with three or four
color-adjacent gluons of negative helicity and the remaining ones of positive
helicity. We provide an explicit analytic formula for the QCD amplitude
A_{6;1}(1^-,2^-,3^-,4^+,5^+,6^+), as well as numerical results for
A_{7;1}(1^-,2^-,3^-,4^+,5^+,6^+,7^+), A_{8;1}(1^-,2^-,3^-,4^+,5^+,6^+,7^+,8^+),
and A_{8;1}(1^-,2^-,3^-,4^-,5^+,6^+,7^+,8^+). We expect the on-shell bootstrap
approach to have widespread applications to phenomenological studies at
colliders.Comment: 77 pages, 17 figures; v2, corrected minor typos in text and small
equation
Gigahertz quantum key distribution with InGaAs avalanche photodiodes
We report a demonstration of quantum key distribution (QKD) at GHz clock
rates with InGaAs avalanche photodiodes (APDs) operating in a self-differencing
mode. Such a mode of operation allows detection of extremely weak avalanches so
that the detector afterpulse noise is sufficiently suppressed. The system is
characterized by a secure bit rate of 2.37 Mbps at 5.6 km and 27.9 kbps at 65.5
km when the fiber dispersion is not compensated. After compensating the fiber
dispersion, the QKD distance is extended to 101 km, resulting in a secure key
rate of 2.88 kbps. Our results suggest that InGaAs APDs are very well suited to
GHz QKD applications.Comment: 4 pages, 4 figure
Spinning test particles and clock effect in Schwarzschild spacetime
We study the behaviour of spinning test particles in the Schwarzschild
spacetime. Using Mathisson-Papapetrou equations of motion we confine our
attention to spatially circular orbits and search for observable effects which
could eventually discriminate among the standard supplementary conditions
namely the Corinaldesi-Papapetrou, Pirani and Tulczyjew. We find that if the
world line chosen for the multipole reduction and whose unit tangent we denote
as is a circular orbit then also the generalized momentum of the
spinning test particle is tangent to a circular orbit even though and
are not parallel four-vectors. These orbits are shown to exist because the spin
induced tidal forces provide the required acceleration no matter what
supplementary condition we select. Of course, in the limit of a small spin the
particle's orbit is close of being a circular geodesic and the (small)
deviation of the angular velocities from the geodesic values can be of an
arbitrary sign, corresponding to the possible spin-up and spin-down alignment
to the z-axis. When two spinning particles orbit around a gravitating source in
opposite directions, they make one loop with respect to a given static observer
with different arrival times. This difference is termed clock effect. We find
that a nonzero gravitomagnetic clock effect appears for oppositely orbiting
both spin-up or spin-down particles even in the Schwarzschild spacetime. This
allows us to establish a formal analogy with the case of (spin-less) geodesics
on the equatorial plane of the Kerr spacetime. This result can be verified
experimentally.Comment: IOP macros, eps figures n. 2, to appear on Classical and Quantum
gravity, 200
Age and the distribution of major injury across a national trauma system
Background
Trauma places a significant burden on healthcare services, and its management impacts greatly on the injured patient. The demographic of major trauma is changing as the population ages, increasingly unveiling gaps in processes of managing older patients. Key to improving patient care is the ability to characterise current patient distribution.
Objectives
There is no contemporary evidence available to characterise how age impacts on trauma patient distribution at a national level. Through an analysis of the Trauma Audit Research Network (TARN) database, we describe the nature of Major Trauma in England since the configuration of regional trauma networks, with focus on injury distribution, ultimate treating institution and any transfer in-between.
Methods
The TARN database was analysed for all patients presenting from April 2012 to the end of October 2017 in NHS England.
Results
About 307,307 patients were included, of which 63.8% presented directly to a non-specialist hospital (trauma unit (TU)). Fall from standing height in older patients, presenting and largely remaining in TUs, dominates the English trauma caseload. Contrary to perception, major trauma patients currently are being cared for in both specialist (major trauma centres (MTCs)) and non-specialist (TU) hospitals. Paediatric trauma accounts for <5% of trauma cases and is focussed on paediatric MTCs.
Conclusions
Within adult major trauma patients in England, mechanism of injury is dominated by low level falls, particularly in older people. These patients are predominately cared for in TUs. This work illustrates the reality of current care pathways for major trauma patients in England in the recently configured regional trauma networks
Autonomous Integrated Receive System (AIRS) requirements definition. Volume 2: Design and development
Functional requirements and specifications are defined for an autonomous integrated receive system (AIRS) to be used as an improvement in the current tracking and data relay satellite system (TDRSS), and as a receiving system in the future tracking and data acquisition system (TDAS). The AIRS provides improved acquisition, tracking, bit error rate (BER), RFI mitigation techniques, and data operations performance compared to the current TDRSS ground segment receive system. A computer model of the AIRS is used to provide simulation results predicting the performance of AIRS. Cost and technology assessments are included
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