14,452 research outputs found
The Bosonic Structure of Fermions
We bosonize fermions by identifying their occupation numbers as the binary
digits of a Bose occupation number. Unlike other schemes, our method allows
infinitely many fermionic oscillators to be constructed from just one bosonic
oscillator.Comment: 7pages, ADP-94-13/T15
A Generic Conceptual Model for Risk Analysis in a Multi-agent Based Collaborative Design Environment
Organised by: Cranfield UniversityThis paper presents a generic conceptual model of risk evaluation in order to manage the risk through
related constraints and variables under a multi-agent collaborative design environment. Initially, a hierarchy
constraint network is developed to mapping constraints and variables. Then, an effective approximation
technique named Risk Assessment Matrix is adopted to evaluate risk level and rank priority after probability
quantification and consequence validation. Additionally, an Intelligent Data based Reasoning Methodology
is expanded to deal with risk mitigation by combining inductive learning methods and reasoning
consistency algorithms with feasible solution strategies. Finally, two empirical studies were conducted to
validate the effectiveness and feasibility of the conceptual model.Mori Seiki – The Machine Tool Compan
The Witten equation, mirror symmetry and quantum singularity theory
For any non-degenerate, quasi-homogeneous hypersurface singularity, we
describe a family of moduli spaces, a virtual cycle, and a corresponding
cohomological field theory associated to the singularity. This theory is
analogous to Gromov-Witten theory and generalizes the theory of r-spin curves,
which corresponds to the simple singularity A_{r-1}.
We also resolve two outstanding conjectures of Witten. The first conjecture
is that ADE-singularities are self-dual; and the second conjecture is that the
total potential functions of ADE-singularities satisfy corresponding
ADE-integrable hierarchies. Other cases of integrable hierarchies are also
discussed.Comment: To appear in Annals of Mathematics. Includes resolution of the Witten
ADE integrable hierarchies conjecture and Witten's ADE self-mirror
conjecture. Several corrections and clarification
Single-shot electro-optic sampling of coherent transition radiation at the A0 Photoinjector
Future collider applications and present high-gradient laser plasma wakefield
accelerators operating with picosecond bunch durations place a higher demand on
the time resolution of bunch distribution diagnostics. This demand has led to
significant advancements in the field of electro-optic sampling over the past
ten years. These methods allow the probing of diagnostic light such as coherent
transition radiation or the bunch wakefields with sub-picosecond time
resolution. Potential applications in shot-to-shot, non-interceptive
diagnostics continue to be pursued for live beam monitoring of collider and
pump-probe experiments. Related to our developing work with electro-optic
imaging, we present results on single-shot electro-optic sampling of the
coherent transition radiation from bunches generated at the A0 photoinjector.Comment: 3 p
Synchroscan streak camera imaging at a 15-MeV photoinjector with emittance exchange
At the Fermilab A0 photoinjector facility, bunch-length measurements of the
laser micropulse and the e-beam micropulse have been done in the past with a
fast single-sweep module of the Hamamatsu C5680 streak camera with an intrinsic
shot-to-shot trigger jitter of 10-20ps. We have upgraded the camera system with
the synchroscan module tuned to 81.25MHz to provide synchronous summing
capability with less than 1.5ps FWHM trigger jitter and a phase-locked delay
box to provide phase stability of ~1ps over 10s of minutes. These steps allowed
us to measure both the UV laser pulse train at 263nm and the e-beam via optical
transition radiation (OTR). Due to the low electron beam energies and OTR
signals, we typically summed over 50 micropulses with 0.25-1nC per micropulse.
The phase-locked delay box allowed us to assess chromatic temporal effects and
instigated another upgrade to an all-mirror input optics barrel. In addition,
we added a slow sweep horizontal deflection plug-in unit to provide dual-sweep
capability for the streak camera. We report on a series of measurements made
during the commissioning of these upgrades including bunch-length and phase
effects using the emittance exchange beamline and simultaneous imaging of a UV
drive laser component, OTR, and the 800nm diagnostics laser.Comment: 26 p
Identifying network communities with a high resolution
Community structure is an important property of complex networks. An
automatic discovery of such structure is a fundamental task in many
disciplines, including sociology, biology, engineering, and computer science.
Recently, several community discovery algorithms have been proposed based on
the optimization of a quantity called modularity (Q). However, the problem of
modularity optimization is NP-hard, and the existing approaches often suffer
from prohibitively long running time or poor quality. Furthermore, it has been
recently pointed out that algorithms based on optimizing Q will have a
resolution limit, i.e., communities below a certain scale may not be detected.
In this research, we first propose an efficient heuristic algorithm, Qcut,
which combines spectral graph partitioning and local search to optimize Q.
Using both synthetic and real networks, we show that Qcut can find higher
modularities and is more scalable than the existing algorithms. Furthermore,
using Qcut as an essential component, we propose a recursive algorithm, HQcut,
to solve the resolution limit problem. We show that HQcut can successfully
detect communities at a much finer scale and with a higher accuracy than the
existing algorithms. Finally, we apply Qcut and HQcut to study a
protein-protein interaction network, and show that the combination of the two
algorithms can reveal interesting biological results that may be otherwise
undetectable.Comment: 14 pages, 5 figures. 1 supplemental file at
http://cic.cs.wustl.edu/qcut/supplemental.pd
The Observable Thermal and Kinetic Sunyaev-Zel'dovich Effect in Merging Galaxy Clusters
The advent of high-resolution imaging of galaxy clusters using the
Sunyaev-Zel'dovich Effect (SZE) provides a unique probe of the astrophysics of
the intracluster medium (ICM) out to high redshifts. To investigate the effects
of cluster mergers on resolved SZE images, we present a high-resolution
cosmological simulation of a 1.5E15 M_sun adiabatic cluster using the TreeSPH
code ChaNGa. This massive cluster undergoes a 10:3:1 ratio triple merger
accompanied by a dramatic rise in its integrated Compton-Y, peaking at z =
0.05. By modeling the thermal SZE (tSZ) and kinetic SZE (kSZ) spectral
distortions of the Cosmic Microwave Background (CMB) at this redshift with
relativistic corrections, we produce various mock images of the cluster at
frequencies and resolutions achievable with current high-resolution SZE
instruments. The two gravitationally-bound merging subclusters account for 10%
and 1% of the main cluster's integrated Compton-Y, and have extended merger
shock features in the background ICM visible in our mock images. We show that
along certain projections and at specific frequencies, the kSZ CMB intensity
distortion can dominate over the tSZ due to the large line of sight velocities
of the subcluster gas and the unique frequency-dependence of these effects. We
estimate that a one-velocity assumption in estimation of line of sight
velocities of the merging subclusters from the kSZ induces a bias of ~10%. This
velocity bias is small relative to other sources of uncertainty in
observations, partially due to helpful bulk motions in the background ICM
induced by the merger. Our results show that high-resolution SZE observations,
which have recently detected strong kSZ signals in subclusters of merging
systems, can robustly probe the dynamical as well as the thermal state of the
ICM.Comment: MNRAS, accepted. 13 pages, 9 figure
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