1,243 research outputs found
Online Makespan Minimization with Parallel Schedules
In online makespan minimization a sequence of jobs
has to be scheduled on identical parallel machines so as to minimize the
maximum completion time of any job. We investigate the problem with an
essentially new model of resource augmentation. Here, an online algorithm is
allowed to build several schedules in parallel while processing . At
the end of the scheduling process the best schedule is selected. This model can
be viewed as providing an online algorithm with extra space, which is invested
to maintain multiple solutions. The setting is of particular interest in
parallel processing environments where each processor can maintain a single or
a small set of solutions.
We develop a (4/3+\eps)-competitive algorithm, for any 0<\eps\leq 1, that
uses a number of 1/\eps^{O(\log (1/\eps))} schedules. We also give a
(1+\eps)-competitive algorithm, for any 0<\eps\leq 1, that builds a
polynomial number of (m/\eps)^{O(\log (1/\eps) / \eps)} schedules. This value
depends on but is independent of the input . The performance
guarantees are nearly best possible. We show that any algorithm that achieves a
competitiveness smaller than 4/3 must construct schedules. Our
algorithms make use of novel guessing schemes that (1) predict the optimum
makespan of a job sequence to within a factor of 1+\eps and (2)
guess the job processing times and their frequencies in . In (2) we
have to sparsify the universe of all guesses so as to reduce the number of
schedules to a constant.
The competitive ratios achieved using parallel schedules are considerably
smaller than those in the standard problem without resource augmentation
Deterministic Priority Mean-payoff Games as Limits of Discounted Games
International audienceInspired by the paper of de Alfaro, Henzinger and Majumdar about discounted -calculus we show new surprising links between parity games and different classes of discounted games
Dissipative Dynamics of a Josephson Junction In the Bose-Gases
The dissipative dynamics of a Josephson junction in the Bose-gases is
considered within the framework of the model of a tunneling Hamiltonian. The
effective action which describes the dynamics of the phase difference across
the junction is derived using functional integration method. The dynamic
equation obtained for the phase difference across the junction is analyzed for
the finite temperatures in the low frequency limit involving the radiation
terms. The asymmetric case of the Bose-gases with the different order
parameters is calculated as well
Evolution of the macroscopically entangled states in optical lattices
We consider dynamics of boson condensates in finite optical lattices under a
slow external perturbation which brings the system to the unstable equilibrium.
It is shown that quantum fluctuations drive the condensate into the maximally
entangled state. We argue that the truncated Wigner approximation being a
natural generalization of the Gross-Pitaevskii classical equations of motion is
adequate to correctly describe the time evolution including both collapse and
revival of the condensate.Comment: 14 pages, 10 figures, Discussion of reversibility of entanglement is
adde
A quantum beam splitter for atoms
An interferometric method is proposed to controllably split an atomic
condensate in two spatial components with strongly reduced population
fluctuations. All steps in our proposal are in current use in cold atom
laboratories, and we show with a theoretical calculation that our proposal is
very robust against imperfections of the interferometer.Comment: 6 pages, 3 figures, revtex
Prototype scintillator cell for an In-based solar neutrino detector
We describe the work carried out at MPIK to design, model, build and
characterize a prototype cell filled with a novel indium-loaded scintillator of
interest for real-time low energy solar neutrino spectroscopy. First, light
propagation in optical modules was studied with experiments and Monte Carlo
simulations. Subsequently a 5 cm x 5 cm x 100 cm prototype detector was set up
and the optical performances of several samples were measured. We first tested
a benchmark PXE-based scintillator, which performed an attenuation length of ~
4.2 m and a photo-electron yield of ~ 730 pe/MeV. Then we measured three
In-loaded samples. At an In-loading of 44 g/l, an energy resolution of ~ 11.6 %
and a spatial resolution of ~ 7 cm were attained for 477 keV recoil electrons.
The long-range attenuation length in the cell was ~1.3 m and the estimated
photo-electron yield ~ 200 pe/MeV. Light attenuation and relative light output
of all tested samples could be reproduced reasonably well by MC. All optical
properties of this system have remained stable over a period of > 1 y.Comment: 57 pages, 19 figures, 10 tables elsevier template for manuscript
submission submitted to NIMA 10 February 200
Bogoliubov theory of entanglement in a Bose-Einstein condensate
We consider a Bose-Einstein condensate which is illuminated by a short
resonant light pulse that coherently couples two internal states of the atoms.
We show that the subsequent time evolution prepares the atoms in an interesting
entangled state called a spin squeezed state. This evolution is analysed in
detail by developing a Bogoliubov theory which describes the entanglement of
the atoms. Our calculation is a consistent expansion in , where
is the number of particles in the condensate, and our theory predict that it is
possible to produce spin squeezing by at least a factor of . Within
the Bogoliubov approximation this result is independent of temperature.Comment: 14 pages, including 5 figures, minor changes in the presentatio
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