7,258 research outputs found
Physical model for the generation of ideal resources in multipartite quantum networking
We propose a physical model for generating multipartite entangled states of
spin- particles that have important applications in distributed quantum
information processing. Our protocol is based on a process where mobile spins
induce the interaction among remote scattering centers. As such, a major
advantage lies on the management of stationary and well separated spins. Among
the generable states, there is a class of -qubit singlets allowing for
optimal quantum telecloning in a scalable and controllable way. We also show
how to prepare Aharonov, W and Greenberger-Horne-Zeilinger states.Comment: 5 pages, 2 figures. Format revise
Similarities and differences of pumping conventional and self-compacting concrete
In Practice, Self-Compacting Concrete (SCC) is Considered as a Simple Extension of Conventional Vibrated Concrete (CVC) When Pumping is Concerned. the Same Equipment, Materials, Pumping Procedures and Guidelines Used for CVC Are Applied When Pumping SCC. on the Other Hand, It Has Been Clearly Shown that the Rheological Properties and the Mix Design of SCC Are Different Than CVC. Can the Same Pumping Principles Employed for CVC Be Applied for SCC? This Paper Compares the Some Published Results of Pumping of CVC with Those for SCC. a First Striking Difference between Pumping of CVC and SCC is the Flow Behaviour in the Pipes. the Flow of CVC is a Plug, Surrounded by a Lubricating Layer, While during the Flow of SCC, Part of the Concrete Volume itself is Sheared Inside the Pipe. as a Result, the Importance of Viscosity Increases in Case of SCC. Due to the Low Yield Stress of SCC, the Behaviour in Bends is Different, But Quite Complex to Study. Due to the Lower Content of Aggregate and Better Stability of SCC, as It is Less Prone to Internal Water Migration, Blocking is Estimated to Occur at Lower Frequency in Case of SCC. © RILEM 2010
Lamb Shift of Laser-Dressed Atomic States
We discuss radiative corrections to an atomic two-level system subject to an
intense driving laser field. It is shown that the Lamb shift of the
laser-dressed states, which are the natural state basis of the combined
atom-laser system, cannot be explained in terms of the Lamb shift received by
the atomic bare states which is usually observed in spectroscopic experiments.
In the final part, we propose an experimental scheme to measure these
corrections based on the incoherent resonance fluorescence spectrum of the
driven atom.Comment: 4 pages, 1 figure, submitted for publicatio
An analog fluid model for some tachyonic effects in field theory
We consider the sound radiation from an acoustic point-like source moving
along a supersonic ("space-like") trajectory in a fluid at rest. We call it an
acoustic "tachyonic" source. We describe the radiation emitted by this
supersonic source. After quantizing the acoustic perturbations, we present the
distribution of phonons generated by this classical tachyonic source and the
classical wave interference pattern.Comment: 14 pages, 5 figures, accepted for publication in Mod. Phys. Lett.
An analytic study of the off-diagonal mass generation for Yang-Mills theories in the maximal Abelian gauge
We investigate a dynamical mass generation mechanism for the off-diagonal
gluons and ghosts in SU(N) Yang-Mills theories, quantized in the maximal
Abelian gauge. Such a mass can be seen as evidence for the Abelian dominance in
that gauge. It originates from the condensation of a mixed gluon-ghost operator
of mass dimension two, which lowers the vacuum energy. We construct an
effective potential for this operator by a combined use of the local composite
operators technique with the algebraic renormalization and we discuss the gauge
parameter independence of the results. We also show that it is possible to
connect the vacuum energy, due to the mass dimension two condensate discussed
here, with the non-trivial vacuum energy originating from the condensate ,
which has attracted much attention in the Landau gauge.Comment: 24 pages, 2 .eps figures. v2: version accepted for publication in
Phys.Rev.
Locally Weyl invariant massless bosonic and fermionic spin-1/2 action in the and space-times
We search for a real bosonic and fermionic action in four dimensions which
both remain invariant under local Weyl transformations in the presence of
non-metricity and contortion tensor. In the presence of the non-metricity
tensor the investigation is extended to Weyl space-time while when
the torsion is encountered we are restricted to the Riemann-Cartan
space-time. Our results hold for a subgroup of the Weyl-Cartan
space-time and we also calculate extra contributions to the conformal gravity.Comment: 16 page
What Fraction of Gravitational Lens Galaxies Lie in Groups?
We predict how the observed variations in galaxy populations with environment
affect the number and properties of gravitational lenses in different
environments. Two trends dominate: lensing strongly favors early-type galaxies,
which tend to lie in dense environments, but dense environments tend to have a
larger ratio of dwarf to giant galaxies than the field. The two effects nearly
cancel, and the distribution of environments for lens and non-lens galaxies are
not substantially different (lens galaxies are slightly less likely than
non-lens galaxies to lie in groups and clusters). We predict that about 20% of
lens galaxies are in bound groups (defined as systems with a line-of-sight
velocity dispersion sigma in the range 200 < sigma < 500 km/s), and another
roughly 3% are in rich clusters (sigma > 500 km/s). Therefore at least roughly
25% of lenses are likely to have environments that significantly perturb the
lensing potential. If such perturbations do not significantly increase the
image separation, we predict that lenses in groups have a mean image separation
that is about 0.2'' smaller than that for lenses in the field and estimate that
20-40 lenses in groups are required to test this prediction with significance.
The tail of the distribution of image separations is already illuminating.
Although lensing by galactic potential wells should rarely produce lenses with
image separations theta >~ 6'', two such lenses are seen among 49 known lenses,
suggesting that environmental perturbations of the lensing potential can be
significant. Further comparison of theory and data will offer a direct probe of
the dark halos of galaxies and groups and reveal the extent to which they
affect lensing estimates of cosmological parameters.Comment: 32 pages, 6 embedded figures; accepted for publication in Ap
Weak nonlinearities: A new route to optical quantum computation
Quantum information processing (QIP) offers the promise of being able to do
things that we cannot do with conventional technology. Here we present a new
route for distributed optical QIP, based on generalized quantum non-demolition
measurements, providing a unified approach for quantum communication and
computing. Interactions between photons are generated using weak
non-linearities and intense laser fields--the use of such fields provides for
robust distribution of quantum information. Our approach requires only a
practical set of resources, and it uses these very efficiently. Thus it
promises to be extremely useful for the first quantum technologies, based on
scarce resources. Furthermore, in the longer term this approach provides both
options and scalability for efficient many-qubit QIP.Comment: 7 Pages, 4 Figure
β-Decay Half-Lives of 76;77Co, 79;80Ni, and 81Cu: Experimental Indication of a Doubly Magic 78Ni
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