7,928 research outputs found
"Only decent girls are employed": the respectability, decency and virtue of the garment workers on the Witwatersrand during the thirties.
Paper presented at the Wits History Workshop: The Making of Class, 9-14 February, 198
Photoassociation spectra and the validity of the dipole approximation for weakly bound dimers
Photoassociation (PA) of ultracold metastable helium to the 2s2p manifold is
theoretically investigated using a non-perturbative close-coupled treatment in
which the laser coupling is evaluated without assuming the dipole
approximation. The results are compared with our previous study [Cocks and
Whittingham, Phys. Rev. A 80, 023417 (2009)] that makes use of the dipole
approximation. The approximation is found to strongly affect the PA spectra
because the photoassociated levels are weakly bound, and a similar impact is
predicted to occur in other systems of a weakly bound nature. The inclusion or
not of the approximation does not affect the resonance positions or widths,
however significant differences are observed in the background of the spectra
and the maximum laser intensity at which resonances are discernable. Couplings
not satisfying the dipole selection rule |J-1| <= J' <= |J+1| do not lead to
observable resonances.Comment: 5 pages, 2 figures; Minor textual revision
The Jacobi identity for Dirac-like brackets
For redundant second-class constraints the Dirac brackets cannot be defined
and new brackets must be introduced. We prove here that the Jacobi identity for
the new brackets must hold on the surface of the second-class constraints. In
order to illustrate our proof we work out explicitly the cases of a fractional
spin particle in 2+1 dimensions and the original Brink-Schwarz massless
superparticle in D=10 dimensions in a Lorentz covariant constraints separation.Comment: 14 pages, Latex. Final version to be published in Int. J. Mod. Phys.
Poisson-Lie T-duality and N=2 superconformal WZNW models on compact groups
The supersymmetric generalization of Pisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups is considered. It is shown
that the role of Drinfeld's doubles play the complexifications of the
corresponding compact groups. These complex doubles are used to define the
natural actions of the isotropic subgroups forming the doubles on the group
manifolds of the N=2 superconformal WZNW models. The Poisson- Lie T-duality in
N=2 superconformal U(2)-WZNW model considered in details. It is shown that this
model admits Poisson-Lie symmetries with respect to the isotropic subgroups
forming Drinfeld's double Gl(2,C). Poisson-Lie T-duality transformation maps
this model into itself but acts nontrivialy on the space of classical
solutions. Supersymmetric generalization of Poisson-Lie T-duality in N=2
superconformal WZNW models on the compact groups of higher dimensions is
proposed.Comment: 12 pages, latex, misprints correcte
Players Indifferent to Cooperate and Characterizations of the Shapley Value
In this paper we provide new axiomatizations of the Shapley value for TU-games using axioms that are based on relational aspects in the interactions among players. Some of these relational aspects, in particular the economic or social interest of each player in cooperating with each other, can be found embedded in the characteristic function. We define a particular relation among the players that it is based on mutual indifference. The first newaxiom expresses that the payoffs of two playerswho are not indifferent to each other are affected in the same way if they become enemies and do not cooperate with each other anymore. The second new axiom expresses that the payoff of a player is not affected if players to whom it is indifferent leave the game. We show that the Shapley value is characterized by these two axioms together with the well-known efficiency axiom. Further, we show that another axiomatization of the Shapley value is obtained if we replace the second axiom and efficiency by the axiom which applies the efficiency condition to every class of indifferent players. Finally, we extend the previous results to the case of weighted Shapley values. © Springer-Verlag Berlin Heidelberg 2012
Constraints on Scalar Phantoms
We update the constraints on the minimal model of dark matter, where a stable
real scalar field is added to the standard model Lagrangian with a
renormalizable coupling to the Higgs field. Once we fix the dark matter
abundance, there are only two relevant model parameters, the mass of the scalar
field and that of the Higgs boson. The recent data from the CDMS II experiment
have excluded a parameter region where the scalar field is light such as less
than about 50 GeV. In a large parameter region, the consistency of the model
can be tested by the combination of future direct detection experiments and the
LHC experiments.Comment: 7 pages, 1 figur
Supertraces on the algebra of observables of the rational Calogero model based on the classical root system
A complete set of supertraces on the algebras of observables of the rational
Calogero models with harmonic interaction based on the classical root systems
of B_N, C_N and D_N types is found. These results extend the results known for
the case A_N. It is shown that there exist Q independent supertraces where
Q(B_N)=Q(C_N) is a number of partitions of N into a sum of positive integers
and Q(D_N) is a number of partitions of N into a sum of positive integers with
even number of even integers.Comment: 10 pages, LATE
Development and evaluation of the elastic recovery concept for expandable space structures
Elastic recovery of expandable space structure
Effect of lightning strike on bromine intercalated graphite fiber/epoxy composites
Laminar composites were fabricated from pristine and bromine intercalated pitch based graphite fibers. It was found that laminar composites could be fabricated using either pristine or intercalated graphite fibers using standard fabrication techniques. The intercalated graphite fiber composites had electrical properties which were markedly improved over both the corresponding pitch based and polyacrylonitrile (PAN) based composites. Despite composites resistivities more than an order of magnitude lower for pitch based fiber composites, the lightning strike resistance was poorer than that of the Pan based fiber composites. This leads to the conclusion that the mechanical properties of the pitch fibers are more important than electrical or thermal properties in determining the lightning strike resistance. Based on indicated lightning strike tolerance for high elongation to failure materials, the use of vapor grown, rather than pitch based graphite fibers appears promising
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