86,120 research outputs found
Density-dependent deformed relativistic Hartree-Bogoliubov theory in continuum
The deformed relativistic Hartree-Bogoliubov theory in continuum with the
density-dependent meson-nucleon couplings is developed. The formulism is
briefly presented with the emphasis on handling the density-dependent
couplings, meson fields, and potentials in axially deformed system with partial
wave method. Taking the neutron-rich nucleus Mg as an example, the newly
developed code is verified by the spherical relativistic continuum
Hartree-Bogoliubov calculations, where only the spherical components of the
densities are considered. When the deformation is included self-consistently,
it is shown that the spherical components of density-dependent coupling
strengths are dominant, while the contributions from low-order deformed
components are not negligible.Comment: 5 pages, 3 figures, and 1 tabl
Neutron halo in deformed nuclei from a relativistic Hartree-Bogoliubov model in a Woods-Saxon basis
Halo phenomenon in deformed nuclei is studied by using a fully
self-consistent deformed relativistic Hartree-Bogoliubov model in a spherical
Woods-Saxon basis with the proper asymptotic behavior at large distance from
the nuclear center. Taking a deformed neutron-rich and weakly bound nucleus
Mg as an example and by examining contributions of the halo, deformation
effects, and large spatial extensions, we show a decoupling of the halo
orbitals from the deformation of the core.Comment: 6 pages, 2 figures, to appear in the proceedings of the International
Nuclear Physics Conference (INPC 2010), July 4-9 2010, Vancouve
Optimal Event-Driven Multi-Agent Persistent Monitoring of a Finite Set of Targets
We consider the problem of controlling the movement of multiple cooperating
agents so as to minimize an uncertainty metric associated with a finite number
of targets. In a one-dimensional mission space, we adopt an optimal control
framework and show that the solution is reduced to a simpler parametric
optimization problem: determining a sequence of locations where each agent may
dwell for a finite amount of time and then switch direction. This amounts to a
hybrid system which we analyze using Infinitesimal Perturbation Analysis (IPA)
to obtain a complete on-line solution through an event-driven gradient-based
algorithm which is also robust with respect to the uncertainty model used. The
resulting controller depends on observing the events required to excite the
gradient-based algorithm, which cannot be guaranteed. We solve this problem by
proposing a new metric for the objective function which creates a potential
field guaranteeing that gradient values are non-zero. This approach is compared
to an alternative graph-based task scheduling algorithm for determining an
optimal sequence of target visits. Simulation examples are included to
demonstrate the proposed methods.Comment: 12 pages full version, IEEE Conference on Decision and Control, 201
Casimir pistons with hybrid boundary conditions
The Casimir effect giving rise to an attractive or repulsive force between
the configuration boundaries that confine the massless scalar field is
reexamined for one to three-dimensional pistons in this paper. Especially, we
consider Casimir pistons with hybrid boundary conditions, where the boundary
condition on the piston is Neumann and those on other surfaces are Dirichlet.
We show that the Casimir force on the piston is always repulsive, in contrast
with the same problem where the boundary conditions are Dirichlet on all
surfaces.Comment: 8 pages, 4 figures,references added, minor typos correcte
Do methanethiol adsorbates on the Au(111) surface dissociate?
The interaction of methanethiol molecules CHSH with the Au(111) surface
is investigated, and it is found for the first time that the S-H bond remains
intact when the methanethiol molecules are adsorbed on the regular Au(111)
surface. However, it breaks if defects are present in the Au(111) surface. At
low coverage, the fcc region is favored for S atom adsorption, but at saturated
coverage the adsorption energies at various sites are almost iso-energetic. The
presented calculations show that a methanethiol layer on the regular Au(111)
surface does not dimerize.Comment: 4 pages, 2 figures, 4 tables, submitted to Phys. Rev. Let
A Nearly Polar Orbit for the Extrasolar Hot Jupiter WASP-79b
We report the measurement of a spin-orbit misalignment for WASP-79b, a
recently discovered, bloated transiting hot Jupiter from the WASP survey. Data
were obtained using the CYCLOPS2 optical-fiber bundle and its simultaneous
calibration system feeding the UCLES spectrograph on the Anglo-Australian
Telescope. We have used the Rossiter-McLaughlin effect to determine the
sky-projected spin-orbit angle to be lambda = -106+19-13 degrees. This result
indicates a significant misalignment between the spin axis of the host star and
the orbital plane of the planet -- the planet being in a nearly polar orbit.
WASP-79 is consistent with other stars that have Teff > 6250K and host hot
Jupiters in spin-orbit misalignment.Comment: 8 pages, 2 figures, in press ApJL (accepted 2 August 2013
The Casimir force of Quantum Spring in the (D+1)-dimensional spacetime
The Casimir effect for a massless scalar field on the helix boundary
condition which is named as quantum spring is studied in our recent
paper\cite{Feng}. In this paper, the Casimir effect of the quantum spring is
investigated in -dimensional spacetime for the massless and massive
scalar fields by using the zeta function techniques. We obtain the exact
results of the Casimir energy and Casimir force for any , which indicate a
symmetry of the two space dimensions. The Casimir energy and Casimir
force have different expressions for odd and even dimensional space in the
massless case but in both cases the force is attractive. In the case of
odd-dimensional space, the Casimir energy density can be expressed by the
Bernoulli numbers, while in the even case it can be expressed by the
-function. And we also show that the Casimir force has a maximum value
which depends on the spacetime dimensions. In particular, for a massive scalar
field, we found that the Casimir force varies as the mass of the field changes.Comment: 9 pages, 5 figures, v2, massive case added, refs. adde
On cost-effective communication network designing
How to efficiently design a communication network is a paramount task for
network designing and engineering. It is, however, not a single objective
optimization process as perceived by most previous researches, i.e., to
maximize its transmission capacity, but a multi-objective optimization process,
with lowering its cost to be another important objective. These two objectives
are often contradictive in that optimizing one objective may deteriorate the
other. After a deep investigation of the impact that network topology, node
capability scheme and routing algorithm as well as their interplays have on the
two objectives, this letter presents a systematic approach to achieve a
cost-effective design by carefully choosing the three designing aspects. Only
when routing algorithm and node capability scheme are elegantly chosen can
BA-like scale-free networks have the potential of achieving good tradeoff
between the two objectives. Random networks, on the other hand, have the
built-in character for a cost-effective design, especially when other aspects
cannot be determined beforehand.Comment: 6 pages, 4 figure
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