18,565 research outputs found
Structure formation by cosmic strings with a cosmological constant
Final published version.Comment: 4 Page
Towards a precession driven dynamo experiment
The most ambitious project within the DREsden Sodium facility for DYNamo and
thermohydraulic studies (DRESDYN) at Helmholtz-Zentrum Dresden-Rossendorf
(HZDR) is the set-up of a precession-driven dynamo experiment. After discussing
the scientific background and some results of water pre-experiments and
numerical predictions, we focus on the numerous structural and design problems
of the machine. We also outline the progress of the building's construction,
and the status of some other experiments that are planned in the framework of
DRESDYN.Comment: 9 pages, 6 figures, submitted to Magnetohydrodynamic
Enhancement of laser cooling by the use of magnetic gradients
We present a laser cooling scheme for trapped ions and atoms using a
combination of laser couplings and a magnetic gradient field. In a
Schrieffer-Wolff transformed picture, this setup cancels the carrier and blue
sideband terms completely resulting in an improved cooling behaviour compared
to standard cooling schemes (e.g. sideband cooling) and allowing cooling to the
vibrational ground state. A condition for optimal cooling rates is presented
and the cooling behaviour for different Lamb-Dicke parameters and spontaneous
decay rates is discussed. Cooling rates of one order of magnitude less than the
trapping frequency are achieved using the new cooling method. Furthermore the
scheme turns out to be robust under deviations from the optimal parameters and
moreover provides good cooling rates also in the multi particle case.Comment: 14 pages, 8 figure
Optical diode based on the chirality of guided photons
Photons are nonchiral particles: their handedness can be both left and right.
However, when light is transversely confined, it can locally exhibit a
transverse spin whose orientation is fixed by the propagation direction of the
photons. Confined photons thus have chiral character. Here, we employ this to
demonstrate nonreciprocal transmission of light at the single-photon level
through a silica nanofibre in two experimental schemes. We either use an
ensemble of spin-polarised atoms that is weakly coupled to the nanofibre-guided
mode or a single spin-polarised atom strongly coupled to the nanofibre via a
whispering-gallery-mode resonator. We simultaneously achieve high optical
isolation and high forward transmission. Both are controlled by the internal
atomic state. The resulting optical diode is the first example of a new class
of nonreciprocal nanophotonic devices which exploit the chirality of confined
photons and which are, in principle, suitable for quantum information
processing and future quantum optical networks
Amplitude analysis of four-body decays using a massively-parallel fitting framework
The GooFit Framework is designed to perform maximum-likelihood fits for
arbitrary functions on various parallel back ends, for example a GPU. We
present an extension to GooFit which adds the functionality to perform
time-dependent amplitude analyses of pseudoscalar mesons decaying into four
pseudoscalar final states. Benchmarks of this functionality show a significant
performance increase when utilizing a GPU compared to a CPU. Furthermore, this
extension is employed to study the sensitivity on the mixing
parameters and in a time-dependent amplitude analysis of the decay . Studying a sample of 50 000 events and setting
the central values to the world average of and , the statistical sensitivities of and are determined
to be and .Comment: Proceedings of the 22nd International Conference on Computing in High
Energy and Nuclear Physics, CHEP 201
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