826 research outputs found
Topological twisting of conformal supercharges
Putting a twisted version of N=4 super Yang-Mills on a curved
four-dimensional manifold generically breaks all conformal supersymmetries. In
the special case where the four-manifold is a cone, we show that exactly two
conformal supercharges remain unbroken. We construct an off-shell formulation
of the theory such that the two unbroken conformal supercharges combine into a
family of topological charges parameterized by CP^1. The resulting theory is
topological in the sense that it is independent of the metric on the
three-dimensional base of the cone.Comment: 1+33 pages; references added, an address change
A Virtual Reality Environment for Multi-Sensor Data Integration
Virtual reality (VR) has typically found applications in industrial design, rapid prototyping and advanced scientific visualization. In this paper, we investigate the use of VR for multi-sensor data integration. We attempt to demonstrate that multiple data types-graphical, functional and measurement can be effectively combined inside of a VR environment. This platform allows the user to rapidly sift through large and complex data sets and isolate features of interest. Furthermore, VR environments can be made to evolve based on system data and user input-this provides the ability to develop scenarios that can be used to make informed decisions. Results demonstrating the effectiveness of this approach are shown using the example of multi-sensor gas transmission pipeline inspection. This work is supported in part by the National Science Foundation award #0216348
Two-twistor particle models and free massive higher spin fields
We present D=3 and D=4 models for massive particles moving in a new type of
enlarged spacetime, with D-1 additional vector coordinates, which after
quantization lead to the towers of massive higher spin (HS) free fields. Two
classically equivalent formulations are presented: one with a hybrid
spacetime/bispinor geometry and a second described by a free two-twistor
dynamics with constraints. After quantization in the D=3 and D=4 cases, the
wave functions are given as functions on the SL(2,R) and SL(2,C) group
manifolds respectively, and describe arbitrary on-shell momenta and spin
degrees of freedom. Finally, the D=6 case and possible supersymmetric
extensions are mentioned.Comment: 37 pages, plain latex, v2. Text in Secs. 1 nd 4 enlarged, references
added. Version to appear in JHE
Theory of Excitonic States in CaB6
We study the excitonic states in CaB6 in terms of the Ginzburg-Landau theory.
By minimizing the free energy and by comparing with experimental results, we
identify two possible ground states with exciton condensation. They both break
time-reversal and inversion symmetries. This leads to various magnetic and
optical properties. As for magnetic properties, it is expected to be an
antiferromagnet, and its spin structure is predicted. It will exhibit the
magnetoelectric effect, and observed novel ferromagnetism in doped samples and
in thin-film and powder samples can arise from this effect. Interesting optical
phenomena such as the nonreciprocal optical effect and the second harmonic
generation are predicted. Their measurement for CaB6 will clarify whether
exciton condensation occurs or not and which of the two states is realized.Comment: 17 pages, 3 figure
FOOD SECURITY IN KINSHASA, COPING WITH ADVERSITY
Food Security and Poverty,
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