21,378 research outputs found
Design of two-dimensional sharp-edged-throat supersonic nozzle with boundary-layer correction
Computer program accounts for effective nozzle geometry changes due to boundary layer displacement thickness. Program input and output are discussed
Review of Spectroscopic Data for Measurements of Stratospheric Species
Results and recommendations from a two day workshop are discussed. A review of the current status of experimental and theoretical spectroscopic data on molecules of stratospheric interest is given along with recommendations for additional research. Methods for disseminating new and existing data are also discussed
Readout scheme of the fullerene-based quantum computer by a single electron transistor
The readout of the quantum spin state is a challenge for any spin-based
quantum computing implementation. We propose a scheme, based on the achieved
technique of single electron transistor (SET), to implement the readout of
electronic spin state inside a doped fullerene by means of the
magnetic dipole-dipole coupling and spin filters. In the presence of an
external magnetic field, we show how to perform the spin state detection by
transforming the information contained in the spin state into the tunneling
current. The robustness of our scheme against sources of error is discussed.Comment: RevTex, 1 table and two figures. Latest versio
Valence Quark Distribution in A=3 Nuclei
We calculate the quark distribution function for 3He/3H in a relativistic
quark model of nuclear structure which adequately reproduces the nucleon
approximation, nuclear binding energies, and nuclear sizes for small nuclei.
The results show a clear distortion from the quark distribution function for
individual nucleons (EMC effect) arising dominantly from a combination of
recoil and quark tunneling effects. Antisymmetrization (Pauli) effects are
found to be small due to limited spatial overlaps. We compare our predictions
with a published parameterization of the nuclear valence quark distributions
and find significant agreement.Comment: 18pp., revtex4, 4 fig
Semi-regular masas of transfinite length
In 1965 Tauer produced a countably infinite family of semi-regular masas in
the hyperfinite factor, no pair of which are conjugate by an
automorphism. This was achieved by iterating the process of passing to the
algebra generated by the normalisers and, for each , finding
masas for which this procedure terminates at the -th stage. Such masas are
said to have length . In this paper we consider a transfinite version of
this idea, giving rise to a notion of ordinal valued length. We show that all
countable ordinals arise as lengths of semi-regular masas in the hyperfinite
factor. Furthermore, building on work of Jones and Popa, we
obtain all possible combinations of regular inclusions of irreducible
subfactors in the normalising tower.Comment: 14 page
Periodically-driven quantum matter: the case of resonant modulations
Quantum systems can show qualitatively new forms of behavior when they are
driven by fast time-periodic modulations. In the limit of large driving
frequency, the long-time dynamics of such systems can often be described by a
time-independent effective Hamiltonian, which is generally identified through a
perturbative treatment. Here, we present a general formalism that describes
time-modulated physical systems, in which the driving frequency is large, but
resonant with respect to energy spacings inherent to the system at rest. Such a
situation is currently exploited in optical-lattice setups, where superlattice
(or Wannier-Stark-ladder) potentials are resonantly modulated so as to control
the tunneling matrix elements between lattice sites, offering a powerful method
to generate artificial fluxes for cold-atom systems. The formalism developed in
this work identifies the basic ingredients needed to generate interesting flux
patterns and band structures using resonant modulations. Additionally, our
approach allows for a simple description of the micro-motion underlying the
dynamics; we illustrate its characteristics based on diverse dynamic-lattice
configurations. It is shown that the impact of the micro-motion on physical
observables strongly depends on the implemented scheme, suggesting that a
theoretical description in terms of the effective Hamiltonian alone is
generally not sufficient to capture the full time-evolution of the system.Comment: 16 pages, 3 figures; includes a new Section III dedicated to the
strong-driving regim
Characterizing the Hofstadter butterfly's outline with Chern numbers
In this work, we report original properties inherent to independent particles
subjected to a magnetic field by emphasizing the existence of regular
structures in the energy spectrum's outline. We show that this fractal curve,
the well-known Hofstadter butterfly's outline, is associated to a specific
sequence of Chern numbers that correspond to the quantized transverse
conductivity. Indeed the topological invariant that characterizes the
fundamental energy band depicts successive stairways as the magnetic flux
varies. Moreover each stairway is shown to be labeled by another Chern number
which measures the charge transported under displacement of the periodic
potential. We put forward the universal character of these properties by
comparing the results obtained for the square and the honeycomb geometries.Comment: Accepted for publication in J. Phys. B (Jan 2009
Neutrino masses or new interactions
Recent proposals to study the mass of the "electron" neutrino at a
sensitivity of 0.3 eV can be used to place limits on the right handed and
scalar charged currents at a level which improves on the present experimental
limits. Indeed the neglect of the possibility of such interactions can lead to
the inference of an incorrect value for the mass, as we illustrate.Comment: 12 pages and 3 figures. Contributed to the XX International Symposium
on Lepton and Photon Interactions at High Energies, Rome, July 2001, and to
the International Europhysics Conference on High Energy Physics, Budapest,
July 2001. Preprint numbers added, misprints correcte
- …