1,224 research outputs found
Problems with interpretation of He ground state
The continuum of He nucleus is studied theoretically in a three-body
He++ model basing on the recent information concerning He
spectrum [Golovkov, \textit{et al.}, Phys. Rev. C \textbf{76}, 021605(R)
(2007)]. The He ground state (g.s.) candidate with structure
for new g.s. energy of He is predicted to be at about
MeV. The peak in the cross section associated with this state may be
shifted to a lower energy (e.g. MeV) when He is populated in
reactions with Li due to peculiar reaction mechanism. Formation of the
low-energy ( keV) ``alternative'' ground state with structure
is highly probable in He in the case of considerable
attraction (e.g. fm) in the s-wave He channel, which properties are
still quite uncertain. This result either questions the existing experimental
low-energy spectrum of He or place a limit on the scattering length in
He channel, which contradicts existing data.Comment: 14 pages, 13 figures, 1 tabl
Static deflection control of flexible beams by piezo-electric actuators
This study deals with the utilization of piezo-electric actuators in controlling the static deformation of flexible beams. An optimum design procedure is presented to enable the selection of the optimal location, thickness and excitation voltage of the piezo-electric actuators in a way that would minimize the deflection of the beam to which these actuators are bonded. Numerical examples are presented to illustrate the application of the developed optimization procedure in minimizing the structural deformation of beams of different materials when subjected to different loading and end conditions using ceramic or polymeric piezo-electric actuators. The results obtained emphasize the importance of the devised rational procedure in designing beam-actuator systems with minimal elastic distortions
Hartman effect and spin precession in graphene
Spin precession has been used to measure the transmission time \tau over a
distance L in a graphene sheet. Since conduction electrons in graphene have an
energy-independent velocity v, one would expect \tau > L/v. Here we calculate
that \tau < L/v at the Dirac point (= charge neutrality point) in a clean
graphene sheet, and we interpret this result as a manifestation of the Hartman
effect (apparent superluminality) known from optics.Comment: 6 pages, 4 figures; v2: added a section on the case of
perpendicularly aligned magnetizations; v3: added a figur
The -matrix inverse scattering approach for coupled channels with different thresholds
The inverse scattering method within the -matrix approach to the two
coupled-channel problem is discussed. We propose a generalization of the
procedure to the case with different thresholds.Comment: 20 pages, 3 figure
Threshold Effects in Multi-channel Coupling and Spectroscopic Factors in Exotic Nuclei
In the threshold region, the cross section and the associated overlap
integral obey the Wigner threshold law that results in the Wigner-cusp
phenomenon. Due to flux conservation, a cusp anomaly in one channel manifests
itself in other open channels, even if their respective thresholds appear at a
different energy. The shape of a threshold cusp depends on the orbital angular
momentum of a scattered particle; hence, studies of Wigner anomalies in weakly
bound nuclei with several low-lying thresholds can provide valuable
spectroscopic information. In this work, we investigate the threshold behavior
of spectroscopic factors in neutron-rich drip-line nuclei using the Gamow Shell
Model, which takes into account many-body correlations and the continuum
effects. The presence of threshold anomalies is demonstrated and the
implications for spectroscopic factors are discussed.Comment: Accepted in Physical Review C Figure correcte
The Faraday Quantum Clock and Non-local Photon Pair Correlations
We study the use of the Faraday effect as a quantum clock for measuring
traversal times of evanescent photons through magneto-refractive structures.
The Faraday effect acts both as a phase-shifter and as a filter for circular
polarizations. Only measurements based on the Faraday phase-shift properties
are relevant to the traversal time measurements. The Faraday polarization
filtering may cause the loss of non-local (Einstein-Podolsky-Rosen) two-photon
correlations, but this loss can be avoided without sacrificing the clock
accuracy. We show that a mechanism of destructive interference between
consecutive paths is responsible for superluminal traversal times measured by
the clock.Comment: 6 figure
Compact and Loosely Bound Structures in Light Nuclei
A role of different components in the wave function of the weakly bound light
nuclei states was studied within the framework of the cluster model, taking
into account of orbitals "polarization". It was shown that a limited number of
structures associated with the different modes of nucleon motion can be of
great importance for such systems. Examples of simple and quite flexible trial
wave functions are given for the nuclei Be, He. Expressions for the
microscopic wave functions of these nuclei were found and used for the
calculation of basic nuclear characteristics, using well known central-exchange
nucleon-nucleon potentials.Comment: 19 pages, 3 ps figure
Quantum Abacus for counting and factorizing numbers
We generalize the binary quantum counting algorithm of Lesovik, Suslov, and
Blatter [Phys. Rev. A 82, 012316 (2010)] to higher counting bases. The
algorithm makes use of qubits, qutrits, and qudits to count numbers in a base
2, base 3, or base d representation. In operating the algorithm, the number n <
N = d^K is read into a K-qudit register through its interaction with a stream
of n particles passing in a nearby wire; this step corresponds to a quantum
Fourier transformation from the Hilbert space of particles to the Hilbert space
of qudit states. An inverse quantum Fourier transformation provides the number
n in the base d representation; the inverse transformation is fully quantum at
the level of individual qudits, while a simpler semi-classical version can be
used on the level of qudit registers. Combining registers of qubits, qutrits,
and qudits, where d is a prime number, with a simpler single-shot measurement
allows to find the powers of 2, 3, and other primes d in the number n. We show,
that the counting task naturally leads to the shift operation and an algorithm
based on the quantum Fourier transformation. We discuss possible
implementations of the algorithm using quantum spin-d systems, d-well systems,
and their emulation with spin-1/2 or double-well systems. We establish the
analogy between our counting algorithm and the phase estimation algorithm and
make use of the latter's performance analysis in stabilizing our scheme.
Applications embrace a quantum metrological scheme to measure a voltage (analog
to digital converter) and a simple procedure to entangle multi-particle states.Comment: 23 pages, 15 figure
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