1,514 research outputs found
Silicon on ceramic process. Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project
The technical and economic feasibility of producing solar-cell-quality sheet silicon was investigated. The sheets were made by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Significant progress was made in all areas of the program
Components of Eleven-dimensional Supergravity with Four Off-shell Supersymmetries
We derive the component structure of 11D, supergravity linearized
around eleven-dimensional Minkowski space. This theory represents 4 local
supersymmetries closing onto 4 of the 11 spacetime translations without the use
of equations of motion. It may be interpreted as adding auxiliary bosons
and auxiliary fermions to the physical supergravity multiplet for a total
of components. These components and their transformations are
organized into representations of .Comment: v3: References added, modified footnote. Published versio
N=1 Supercurrents of Eleven-dimensional Supergravity
Eleven-dimensional supergravity can be formulated in superspaces locally of
the form where is 4D conformal superspace
and is an arbitrary 7-manifold admitting a -structure. The
eleven-dimensional 3-form and the stable 3-form on define the lowest
component of a gauge superfield on that is chiral as a
superfield on . This chiral field is part of a tensor hierarchy
giving rise to a superspace Chern-Simons action and its real field strength
defines a lifting of the Hitchin functional on to the superspace
. These terms are those of lowest order in a superspace
Noether expansion in seven conformal gravitino superfields . In
this paper, we compute the action to all orders in the remaining
fields. The eleven-dimensional origin of the resulting non-linear structures is
parameterized by the choice of a complex spinor on encoding the off-shell
4D subalgebra of the eleven-dimensional super-Poincare algebra
Rigidly Supersymmetric Gauge Theories on Curved Superspace
In this note we construct rigidly supersymmetric gauged sigma models and
gauge theories on certain Einstein four-manifolds, and discuss constraints on
these theories. In work elsewhere, it was recently shown that on some
nontrivial Einstein four-manifolds such as AdS, N=1 rigidly supersymmetric
sigma models are constrained to have target spaces with exact K\"ahler forms.
Similarly, in gauged sigma models and gauge theories, we find that
supersymmetry imposes constraints on Fayet-Iliopoulos parameters, which have
the effect of enforcing that K\"ahler forms on quotient spaces be exact. We
also discuss general aspects of universality classes of gauged sigma models, as
encoded by stacks, and also discuss affine bundle structures implicit in these
constructions.Comment: 23 pages; references added; more discussion added; v4: typos fixe
Three-dimensional (p,q) AdS superspaces and matter couplings
We introduce N-extended (p,q) AdS superspaces in three space-time dimensions,
with p+q=N and p>=q, and analyse their geometry. We show that all (p,q) AdS
superspaces with X^{IJKL}=0 are conformally flat. Nonlinear sigma-models with
(p,q) AdS supersymmetry exist for p+q4 the target space geometries
are highly restricted). Here we concentrate on studying off-shell N=3
supersymmetric sigma-models in AdS_3. For each of the cases (3,0) and (2,1), we
give three different realisations of the supersymmetric action. We show that
(3,0) AdS supersymmetry requires the sigma-model to be superconformal, and
hence the corresponding target space is a hyperkahler cone. In the case of
(2,1) AdS supersymmetry, the sigma-model target space must be a non-compact
hyperkahler manifold endowed with a Killing vector field which generates an
SO(2) group of rotations of the two-sphere of complex structures.Comment: 52 pages; V3: minor corrections, version published in JHE
Six-dimensional Supergravity and Projective Superfields
We propose a superspace formulation of N=(1,0) conformal supergravity in six
dimensions. The corresponding superspace constraints are invariant under
super-Weyl transformations generated by a real scalar parameter. The known
variant Weyl super-multiplet is recovered by coupling the geometry to a
super-3-form tensor multiplet. Isotwistor variables are introduced and used to
define projective superfields. We formulate a locally supersymmetric and
super-Weyl invariant action principle in projective superspace. Some families
of dynamical supergravity-matter systems are presented.Comment: 39 pages; v3: some modifications in section 2; equations (2.3),
(2.14b), (2.16) and (2.17) correcte
N=2 Conformal Superspace in Four Dimensions
We develop the geometry of four dimensional N=2 superspace where the entire
conformal algebra of SU(2,2|2) is realized linearly in the structure group
rather than just the SL(2,C) x U(2)_R subgroup of Lorentz and R-symmetries,
extending to N=2 our prior result for N=1 superspace. This formulation
explicitly lifts to superspace the existing methods of the N=2 superconformal
tensor calculus; at the same time the geometry, when degauged to SL(2,C) x
U(2)_R, reproduces the existing formulation of N=2 conformal supergravity
constructed by Howe.Comment: 43 pages; v2 references added, acknowledgments update
Comparison of the effects of superior colliculus and pulvinar lesions on visual search and tachistoscopic pattern discrimination in monkeys
In order to investigate whether pulvinar lesions produce behavioral impairments similar to those that follow superior colliculus lesions, monkeys were tested on a visual search task before and after receiving radiofrequency lesions of either the superior colliculus or pulvinar. The animals searched for a small target pattern within an array of varying numbers of irrelevant patterns. After receiving colliculus lesions, the animals showed marked postoperative increases in either search time, percent errors, or both. By contrast, pulvinar lesions had little or no effect on visual search performance. Similarly, in learning to search for a target they had not previously seen, animals with colliculus lesions were impaired relative to unoperated controls, whereas pulvinar-lesioned animals did not differ from controls. In an attempt to confirm the finding that pulvinar lesions impair tachistoscopic pattern discrimination, we determined exposure-duration thresholds of pulvinar- and colliculus-lesioned monkeys for performance of a pattern discrimination. The thresholds of the colliculus-lesioned monkeys were elevated 20-fold relative to controls. By contrast, thresholds of the pulvinar-lesioned monkeys were normal. We conclude that the pulvinar is not critical for the attentional processes in which the superior colliculus participates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46559/1/221_2004_Article_BF00247037.pd
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