63,096 research outputs found
BRST Analysis of Physical Fields and States for 4D Quantum Gravity on R x S^3
We consider the background-free quantum gravity based on conformal gravity
with the Riegert-Wess-Zumino action, which is formulated in terms of a
conformal field theory. Employing the background in practice, we
construct the nilpotent BRST operator imposing diffeomorphism invariance.
Physical fields and states are analyzed, which are given only by real primary
scalars with a definite conformal weight. With attention to the presence of
background charges, various significant properties, such as the state-operator
correspondence and the norm structure, are clarified with some examples.Comment: 29 pages, several descriptions written using CFT terminology are
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Large-Scale Simulation of Beam Dynamics in High Intensity Ion Linacs Using Parallel Supercomputers
In this paper we present results of using parallel supercomputers to simulate
beam dynamics in next-generation high intensity ion linacs. Our approach uses a
three-dimensional space charge calculation with six types of boundary
conditions. The simulations use a hybrid approach involving transfer maps to
treat externally applied fields (including rf cavities) and parallel
particle-in-cell techniques to treat the space-charge fields. The large-scale
simulation results presented here represent a three order of magnitude
improvement in simulation capability, in terms of problem size and speed of
execution, compared with typical two-dimensional serial simulations. Specific
examples will be presented, including simulation of the spallation neutron
source (SNS) linac and the Low Energy Demonstrator Accelerator (LEDA) beam halo
experiment
Weak Factorizations of the Hardy space in terms of Multilinear Riesz Transforms
This paper provides a constructive proof of the weak factorizations of the
classical Hardy space in terms of multilinear Riesz
transforms. As a direct application, we obtain a new proof of the
characterization of (the dual of )
via commutators of the multilinear Riesz transforms.Comment: improved some typo
Manipulating Majorana fermions in one-dimensional spin-orbit coupled atomic Fermi gases
Majorana fermions are promising candidates for storing and processing
information in topological quantum computation. The ability to control such
individual information carriers in trapped ultracold atomic Fermi gases is a
novel theme in quantum information science. However, fermionic atoms are
neutral and thus are difficult to manipulate. Here, we theoretically
investigate the control of emergent Majorana fermions in one-dimensional
spin-orbit coupled atomic Fermi gases. We discuss (i) how to move Majorana
fermions by increasing or decreasing an effective Zeeman field, which acts like
a solid state control voltage gate; and (ii) how to create a pair of Majorana
fermions by adding a magnetic impurity potential. We discuss the experimental
realization of our control scheme in an ultracold Fermi gas of K atoms.Comment: 4 papges, 6 figure
Human environmental heat transfer simulation with CFD – the advances and challenges
The modelling and prediction of human thermoregulatory responses and comfort have gone a long way during the past decades. Sophisticated and detailed human models, i.e. the active multi-nodal thermal models with physiological regulatory responses, have been developed and widely adopted
in both research and industrial practice. The recent trend is to integrate human models with environmental models in order to provide more insight into the thermal comfort issues, especially in the non-homogeneous and transient conditions. This paper reviews the logics and expectations of coupling human models with computational fluid dynamics
(CFD) models. One of main objectives of such approaches is to take the advantage of the high resolution achievable with the CFD, to replace the empirical methods used in the human models. We aim to initiate debates on the validity of this objective, and to identify the technical requirements
for achieving this goal. A simple experiment with 3D human models of different sizes and shapes is also reported. Initial results shows the presence of arms may be important. Further experiments are required to establish the impact of size and shape on simulation result
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Integration, management and communication of heterogeneous design resources with WWW technologies
Recently, advanced information technologies have opened new pos-sibilities for collaborative designs. In this paper, a Web-based collaborative de-sign environment is proposed, where heterogeneous design applications can be integrated with a common interface, managed dynamically for publishing and searching, and communicated with each other for integrated multi-objective de-sign. The CORBA (Common Object Request Broker Architecture) is employed as an implementation tool to enable integration and communication of design application programs; and the XML (eXtensible Markup Language) is used as a common data descriptive language for data exchange between heterogeneous applications and for resource description and recording. This paper also intro-duces the implementation of the system and the encapsulating issues of existing legacy applications. At last, an example of gear design based on the system is il-lustrated to identify the methods and procedure developed by this research
A super-ductile alloy for the die-casting of aluminium automotive body structural components
Super-ductile die-cast aluminium alloys are critical to future light-weighting of automotive body structures. This paper introduces a die-cast aluminium alloy that can satisfy the requirements of these applications. After a review of currently available alloys, the requirement of a die-cast aluminium alloy for automotive body structural parts is proposed and an Al-Mg-Si system is suggested. The effect of the alloying elements, in the composition, has been investigated on the microstructure and mechanical properties, in particular the yield strength, the ultimate tensile strength and elongation. © (2014) Trans Tech Publications, Switzerland.The EPSRC and JLR U
BRST Invariant Higher Derivative Operators in 4D Quantum Gravity based on CFT
We continue the study of physical fields for the background free 4D quantum
gravity based on the Riegert-Wess-Zumino action, developed in Phys. Rev. D {\bf
85} (2012) 024028. The background free model is formulated in terms of a
certain conformal field theory on M^4 in which conformal symmetry arises as
gauge symmetry, namely diffeomorphism invariance. In this paper, we construct
the physical field operator corresponding to any integer power of Ricci scalar
curvature in the context of the BRST quantization. We also discuss how to
define the correlation function and its physical meanings.Comment: 22 pages, minor typo corrected, published versio
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