845 research outputs found
Upper limits of particle emission from high-energy collision and reaction near a maximally rotating Kerr black hole
The center-of-mass energy of two particles colliding near the horizon of a
maximally rotating black hole can be arbitrarily high if the angular momentum
of either of the incident particles is fine-tuned, which we call a critical
particle. We study particle emission from such high-energy collision and
reaction in the equatorial plane fully analytically. We show that the
unconditional upper limit of the energy of the emitted particle is given by
218.6% of that of the injected critical particle, irrespective of the details
of the reaction and this upper limit can be realized for massless particle
emission. The upper limit of the energy extraction efficiency for this emission
as a collisional Penrose process is given by 146.6%, which can be realized in
the collision of two massive particles with optimized mass ratio. Moreover, we
analyze perfectly elastic collision, Compton scattering, and pair annihilation
and show that net positive energy extraction is really possible for these three
reactions. The Compton scattering is most efficient among them and the
efficiency can reach 137.2%. On the other hand, our result is qualitatively
consistent with the earlier claim that the mass and energy of the emitted
particle are at most of order the total energy of the injected particles and
hence we can observe neither super-heavy nor super-energetic particles.Comment: 22 pages, 3 figures, typos corrected, reference updated, accepted for
publication in Physical Review D, typos correcte
Quantum Dynamics of Three Coupled Atomic Bose-Einstein Condensates
The simplest model of three coupled Bose-Einstein Condensates (BEC) is
investigated using a group theoretical method. The stationary solutions are
determined using the SU(3) group under the mean field approximation. This
semiclassical analysis using the system symmetries shows a transition in the
dynamics of the system from self trapping to delocalization at a critical value
for the coupling between the condensates. The global dynamics are investigated
by examination of the stable points and our analysis shows the structure of the
stable points depends on the ratio of the condensate coupling to the
particle-particle interaction, undergoes bifurcations as this ratio is varied.
This semiclassical model is compared to a full quantum treatment, which also
displays the dynamical transition. The quantum case has collapse and revival
sequences superposed on the semiclassical dynamics reflecting the underlying
discreteness of the spectrum. Non-zero circular current states are also
demonstrated as one of the higher dimensional effects displayed in this system.Comment: Accepted to PR
A symmetry analyser for non-destructive Bell state detection using EIT
We describe a method to project photonic two-qubit states onto the symmetric
and antisymmetric subspaces of their Hilbert space. This device utilizes an
ancillary coherent state, together with a weak cross-Kerr non-linearity,
generated, for example, by electromagnetically induced transparency. The
symmetry analyzer is non-destructive, and works for small values of the
cross-Kerr coupling. Furthermore, this device can be used to construct a
non-destructive Bell state detector.Comment: Final published for
Proton-Deuteron Elastic Scattering from 2.5 to 22.5 MeV
We present the results of a calculation of differential cross sections and
polarization observables for proton-deuteron elastic scattering, for proton
laboratory energies from 2.5 to 22.5 MeV. The Paris potential parametrisation
of the nuclear force is used. As solution method for the charged-composite
particle equations the 'screening and renormalisation approach' is adopted
which allows to correctly take into account the Coulomb repulsion between the
two protons. Comparison is made with the precise experimental data of Sagara et
al. [Phys. Rev. C 50, 576 (1994)] and of Sperison et al. [Nucl. Phys. A422, 81
(1984)].Comment: 24 pages, 8 eps figures, uses REVTe
A Reilly formula and eigenvalue estimates for differential forms
We derive a Reilly-type formula for differential p-forms on a compact
manifold with boundary and apply it to give a sharp lower bound of the spectrum
of the Hodge Laplacian acting on differential forms of an embedded hypersurface
of a Riemannian manifold. The equality case of our inequality gives rise to a
number of rigidity results, when the geometry of the boundary has special
properties and the domain is non-negatively curved. Finally we also obtain, as
a by-product of our calculations, an upper bound of the first eigenvalue of the
Hodge Laplacian when the ambient manifold supports non-trivial parallel forms.Comment: 22 page
On contribution of three-body forces to interaction at intermediate energies
Available data on large-angle nucleon-deuteron elastic scattering
below the pion threshold give a signal for three-body forces. There is a
problem of separation of possible subtle aspects of these forces from off-shell
effects in two-nucleon potentials.
By considering the main mechanisms of the process, we show qualitatively that
in the quasi-binary reaction with the final spin singlet
NN-pair in the S-state the relative contribution of the 3N forces differs
substantially from the elastic channel.
It gives a new testing ground for the problem in question.Comment: 9 pages, Latex, 3 Postscript figure
Multiple-photon resolving fiber-loop detector
We show first reconstructions of the photon-number distribution obtained with
a multi-channel fiber-loop detector. Apart from analyzing the statistics of
light pulses this device can serve as a sophisticated postselection device for
experiments in quantum optics and quantum information. We quantify its
efficiency by means of the Fisher information and compare it to the efficiency
of the ideal photodetector.Comment: 5 pages, 6 figure
Memory Effect, Rejuvenation and Chaos Effect in the Multi-layer Random Energy Model
We introduce magnetization to the Multi-layer Random Energy Model which has a
hierarchical structure, and perform Monte Carlo simulation to observe the
behavior of ac-susceptibility. We find that this model is able to reproduce
three prominent features of spin glasses, i.e., memory effect, rejuvenation and
chaos effect, which were found recently by various experiments on aging
phenomena with temperature variations.Comment: 10 pages, 14 figures, to be submitted to J. Phys. Soc. Jp
Laser-triggered ion acceleration and table top isotope production
We have observed deuterons accelerated to energies of about 2 MeV in the interaction of relativistically intense 10 TW, 400 fs laser pulse with a thin layer of deuterated polystyrene deposited on Mylar film. These high-energy deuterons were directed to the boron sample, where they produced ⌠105âŒ105 atoms of positron active isotope 11C11C from the reaction 10B(d,n)11C.10B(d,n)11C. The activation results suggest that deuterons were accelerated from the front surface of the target. © 2001 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70713/2/APPLAB-78-5-595-1.pd
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