5,201 research outputs found
U-duality in three and four dimensions
Using generalised geometry we study the action of U-duality acting in three
and four dimensions on the bosonic fields of eleven dimensional supergravity.
We compare the U-duality symmetry with the T-duality symmetry of double field
theory and see how the and SL(5) U-duality groups reduce
to the SO(2,2) and SO(3,3) T-duality symmetry groups of the type IIA theory. As
examples we dualise M2-branes, both black and extreme. We find that uncharged
black M2-branes become charged under U-duality, generalising the Harrison
transformation, while extreme M2-branes will become new extreme M2-branes. The
resulting tension and charges are quantised appropriately if we use the
discrete U-duality group .Comment: v1: 35 pages; v2: minor corrections in section 4.1.2, many references
added; v3: further discussion added on the conformal factor of the
generalised metric in section 2 and on the Wick-rotation used to construct
examples in section
Quantization on a torus without position operators
We formulate quantum mechanics in the two-dimensional torus without using
position operators. We define an algebra with only momentum operators and shift
operators and construct irreducible representation of the algebra. We show that
it realizes quantum mechanics of a charged particle in a uniform magnetic
field. We prove that any irreducible representation of the algebra is unitary
equivalent to each other. This work provides a firm foundation for the
noncommutative torus theory.Comment: 12 pages, LaTeX2e, the title is changed, minor corrections are made,
references are added. To be published in Modern Physics Letters
Management Systems For Operational Processing Of Launch Vehicles
This paper summarizes the status of management information systems with emphasis on applications to planning and management of airline maintenance and refurbishment operations. Past approaches to management of launch operations are reviewed and analyzed for their applicability to the Space Shuttle era. Factors affecting the selection of a management information system for the Shuttle will be analyzed and discussed
Accountants\u27 Liability after Bily v. Arthur Young & Co.: A More Equitable Proposal for Third Party Recovery
In today\u27s business world, the unqualified opinion -an auditor\u27s statement that a business\u27s financial statements conform to accounting industry standards-has become a prerequisite for attracting investment in business ventures. When third parties are economically injured after relying on such opinions, the question arises whether the auditor owes a duty of care to third parties.
From 1986 until 1992, California\u27s answer was that an accountant was liable for injury to a third party if that injury was reasonably foreseeable. The 1992 California Supreme Court decision Bily v. Arthur Young discarded this approach in favor of new standard. The new standard requires a third party plaintiff to show that the accountant actually foresaw reliance by the third party.
This Note criticizes the court\u27s reasoning in Bily. The court adopted this approach to protect accountants from disproportionate liability. However, the approach also has the effect of unjustly limiting the availability of recovery for injured third parties where reliance was reasonably foreseeable, but not actually foreseen, by the accountant.
The author suggests that the California legislature should pass legislation overruling Bily. To reconcile the interests of injured third parties and accountants, the new approach would combine reasonable foreseeability and proportionate liability. This approach would strike an equitable balance; accountants would be protected from disproportionate liability and injured third parties would be afforded an avenue of recovery
Thermal expansion properties of composite materials
Thermal expansion data for several composite materials, including generic epoxy resins, various graphite, boron, and glass fibers, and unidirectional and woven fabric composites in an epoxy matrix, were compiled. A discussion of the design, material, environmental, and fabrication properties affecting thermal expansion behavior is presented. Test methods and their accuracy are discussed. Analytical approaches to predict laminate coefficients of thermal expansion (CTE) based on lamination theory and micromechanics are also included. A discussion is included of methods of tuning a laminate to obtain a near-zero CTE for space applications
Three results on representations of Mackey Lie algebras
I. Penkov and V. Serganova have recently introduced, for any non-degenerate
pairing of vector spaces, the Lie algebra
consisting of endomorphisms of whose
duals preserve . In their work, the category
of -modules which are finite
length subquotients of the tensor algebra is singled out and
studied. In this note we solve three problems posed by these authors concerning
the categories . Denoting by
the category with the same objects as
but regarded as -modules, we first
show that when and are paired by dual bases, the functor
taking a module to
its largest weight submodule with respect to a sufficiently nice Cartan
subalgebra of is a tensor equivalence. Secondly, we prove that
when and are countable-dimensional, the objects of
have finite length as -modules.
Finally, under the same hypotheses, we compute the socle filtration of a simple
object in as a -module.Comment: 9 page
Iterated function systems, representations, and Hilbert space
This paper studies a general class of Iterated Function Systems (IFS). No
contractivity assumptions are made, other than the existence of some compact
attractor. The possibility of escape to infinity is considered. Our present
approach is based on Hilbert space, and the theory of representations of the
Cuntz algebras O_n, n=2,3,.... While the more traditional approaches to IFS's
start with some equilibrium measure, ours doesn't. Rather, we construct a
Hilbert space directly from a given IFS; and our construction uses instead
families of measures. Starting with a fixed IFS S_n, with n branches, we prove
existence of an associated representation of O_n, and we show that the
representation is universal in a certain sense. We further prove a theorem
about a direct correspondence between a given system S_n, and an associated
sub-representation of the universal representation of O_n.Comment: 22 pages, 3 figures containing 7 EPS graphics; LaTeX2e ("elsart"
document class); v2 reflects change in Comments onl
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