31,396 research outputs found
Effects of uncertainties and errors on Lyapunov control
Lyapunov control (open-loop) is often confronted with uncertainties and
errors in practical applications. In this paper, we analyze the robustness of
Lyapunov control against the uncertainties and errors in quantum control
systems. The analysis is carried out through examinations of uncertainties and
errors, calculations of the control fidelity under influences of the
certainties and errors, as well as discussions on the caused effects. Two
examples, a closed control system and an open control system, are presented to
illustrate the general formulism.Comment: 4 pages, 5 figure
Effects of Line-tying on Resistive Tearing Instability in Slab Geometry
The effects of line-tying on resistive tearing instability in slab geometry
is studied within the framework of reduced magnetohydrodynamics
(RMHD).\citep{KadomtsevP1974,Strauss1976} It is found that line-tying has a
stabilizing effect. The tearing mode is stabilized when the system length
is shorter than a critical length , which is independent of the
resistivity . When is not too much longer than , the
growthrate is proportional to . When is sufficiently long,
the tearing mode scaling is recovered. The transition
from to occurs at a transition length
.Comment: Correct a typ
Comment on "Peierls Gap in Mesoscopic Ring Threated by a Magnetic Flux"
In a recent letter, Yi et al. PRL 78, 3523 (1997), have considered the
stability of a Charge Density Wave in a one-dimensional ring, in the presence
of an Aharonov-Bohm flux. This comment shows that, in one dimension, the
stability of the Charge Density Wave depends on the parity of the number of
electrons in the ring. This effect is similar to the parity effect known for
the persistent current in one-dimensional rings.Comment: Latex, 1 page, 2 figure
Suppression of ferromagnetic ordering in doped manganites: Effects of the superexchange interaction
From a Monte Carlo study of the ferromagnetic Kondo lattice model for doped
manganites, including the antiferromagnetic superexchange interaction
(), we found that the ferromagnetic ordering was suppressed as
increased. The ferromagnetic transition temperature , as obtained from a
mean field fit to the calculated susceptibilities, was found to decrease
monotonically with increasing . Further, the suppression in
scales with the bandwidth narrowing induced by the antiferromagnetic
frustration originating from . From these results, we propose that the
change in the superexchange interaction strength between the electrons
of the Mn ions is one of the mechanisms responsible for the suppression in
observed in manganites of the type
(LaPr)CaMnO.Comment: 5 pages, 6 figures. To appear in PR
InGaAsP p-i-n photodiodes for optical communication at the 1.3-µm wavelength
The preparation and properties of Cd-diffused p-n homojunction InGaAsP photodiodes designed specifically for operation at the 1.3-µm wavelength are described. At a reverse bias of 10 V, the dark current of these diodes was as low as 15 pA. The peak responsivity at 1.3-µm wavelength was 0.7 A/W. An impulse response (full width at half maximum) of 60 ps and a 3-dB bandwidth of 5.5 GHz were achieved.
Atom-molecule conversion with particle losses
Based on the mean-field approximation and the phase space analysis, we study
the dynamics of an atom-molecule conversion system subject to particle loss.
Starting from the many-body dynamics described by a master equation, an
effective nonlinear Schr\"odinger equation is introduced. The classical phase
space is then specified and classified by fixed points. The boundary, which
separate different dynamical regimes have been calculated and discussed. The
effect of particle loss on the conversion efficiency and the self-trapping is
explored.Comment: 6 pages, 5 figure
Constructive Wall-Crossing and Seiberg-Witten
We outline a comprehensive and first-principle solution to the wall-crossing
problem in D=4 N=2 Seiberg-Witten theories. We start with a brief review of the
multi-centered nature of the typical BPS states and recall how the
wall-crossing problem thus becomes really a bound state formation/dissociation
problem. Low energy dynamics for arbitrary collections of dyons is derived,
from Seiberg-Witten theory, with the proximity to the so-called marginal
stability wall playing the role of the small expansion parameter. We find that,
surprisingly, the low energy dynamics of n+1 BPS dyons cannot
be consistently reduced to the classical moduli space, \CM, yet the index can
be phrased in terms of \CM. We also explain how an equivariant version of
this index computes the protected spin character of the underlying field
theory, where SO(3)_\CJ isometry of \CM turns out to be the diagonal
subgroup of spatial rotation and R-symmetry. The so-called
rational invariants, previously seen in the Kontsevich-Soibelman formalism of
wall-crossing, are shown to emerge naturally from the orbifolding projection
due to Bose/Fermi statistics.Comment: 25 pages, conference proceeding contribution for "Progress of Quantum
Field Theory and String Theory," Osaka, April 201
- …