170,915 research outputs found
A parallel and adaptive multigrid solver for the solutions of the optimal control of geometric evolution laws in two and three dimensions
We present a problem concerning the optimal control of geometric evolution laws. This is a minimisation problem that aims to find a control η which minimises the objective functional J subject to some imposed constraints. We apply this methodology to an application of whole cell tracking. Given two sets of data of cell morphologies, we may solve the optimal control problem to dynamically reconstruct the cell movements between the time frame of these two sets of data. This problem is solved in two and three space dimensions, using a state-of-the-art numerical method, namely multigrid, with adaptivity and parallelism
Zirconium carbide as an electrocatalyst for the chromous-chromic redox couple
Zirconium carbide is used as a catalyst in a REDOX cell for the oxidation of chromous ions to chromic ions and for the reduction of chromic ions to chromous ions. The zirconium carbide is coated on an inert electronically conductive electrode which is present in the anode fluid of the cell
D^0-D^0bar mixing in \Upsilon(1S) \to D^0 D^0bar decay at Super-B
\Dz-\Dzb mixing and significant CP violation in the charm system may
indicate the signature of new physics. In this study, we suggest that the
coherent \DzDzb events from the decay of \Upsilon(1S) \to \Dz \Dzb can be
used to measure both mixing parameters and CP violation in charm decays. The
neutral mesons from decay are strongly boosted, so that it
will offer the possibility to measure the proper-time interval, ,
between the fully-reconstructed \Dz and \Dzb. Both coherent and
time-dependent information can be used to extract \Dz-\Dzb mixing parameters.
The sensitivity of the measurement should be improved at B factories or
super-B.Comment: 6 pages, 1 figure, this is the last version to appear in Phys. Rev.
Dispersive Cylindrical Cloaks under Non-Monochromatic Illumination
Transformation-based cylindrical cloaks and concentrators are illuminated
with non-monochromatic waves and unusual effects are observed with interesting
potential applications. The transient responses of the devices are studied
numerically with the Finite-Difference Time-Domain method and the results are
verified with analytical formulas. We compute the effective bandwidth of
several cloaking schemes as well as the effect of losses on the performance of
the structures. We also find that narrowband behavior, frequency shift effects,
time delays and spatial disturbances of the incoming waves are dominant due to
the inherently dispersive nature of the devices. These effects are important
and should be taken into account when designing metamaterial-based devices.Comment: 12 pages, 9 figure
Rashba spin splitting in biased semiconductor quantum wells
Rashba spin splitting (RSS) in biased semiconductor quantum wells is
investigated theoretically based on the eight-band envelope function model. We
find that at large wave vectors, RSS is both nonmonotonic and anisotropic as a
function of in-plane wave vector, in contrast to the widely used linear and
isotropic model. We derive an analytical expression for RSS, which can
correctly reproduce such nonmonotonic behavior at large wave vectors. We also
investigate numerically the dependence of RSS on the various band parameters
and find that RSS increases with decreasing band gap and subband index,
increasing valence band offset, external electric field, and well width. Our
analytical expression for RSS provides a satisfactory explanation to all these
features.Comment: 5 pages, 4 figures, author names corrected, submitted to Phys. Rev.
Noncommutativity as a Possible Origin of the Ultrahigh Energy Cosmic Ray and the TeV-photon Paradoxes
In this paper, we present a general modified dispersion relation derived from
q-deformed noncommutative theory and apply it to the ultrahigh energy cosmic
ray and the TeV-photon paradoxes--threshold anomalies. Our purpose is not only
trying to solve these puzzles by noncommutative theory but also to support
noncommutative theory through the coincidence of the region in the parameter
space for resolving the threshold anomalies with the one from the q-deformed
noncommutative theory.Comment: 9 pages, 1 figur
Effective spin model for the spin-liquid phase of the Hubbard model on the triangular lattice
We show that the spin liquid phase of the half-filled Hubbard model on the
triangular lattice can be described by a pure spin model. This is based on a
high-order strong coupling expansion (up to order 12) using perturbative
continuous unitary transformations. The resulting spin model is consistent with
a transition from three-sublattice long-range magnetic order to an insulating
spin liquid phase, and with a jump of the double occupancy at the transition.
Exact diagonalizations of both models show that the effective spin model is
quantitatively accurate well into the spin liquid phase, and a comparison with
the Gutzwiller projected Fermi sea suggests a gapless spectrum and a spinon
Fermi surface.Comment: 4 pages, 4 figures, published versions with additional dat
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