2,373 research outputs found
Inverse scattering procedures for the reconstruction of one-dimensional permittivity range profile
In the present work we have presented a reliable and efficient algorithm for the data inversion, which is based on a fully nonlinear data model in conjunction with an optimization technique. The reconstruction of the permittivity range profile has been tested both on
synthetic and real data to validate the electromagnetic code as well as to assess the accuracy and efficiency of the reconstruction procedure. We have studied the resolution of the algorithm and its robustness to the noise, demonstrating the ability of our procedure to be able to recognize the presence of high discontinuities even independently from the discretization fixed by the user.
As a part of the ongoing improvement of the presented method, we have addressed the implementation of a new optimization algorithm, namely the particle swarm optimization, which has been customized and enhanced for our purposes.
Finally, a detailed description of a fast and efficient procedure to evaluate the green’s function for a multilayered medium has been given. This is the groundwork useful for the next step toward a more reliable and versatile forward solver to be implemented in the inversion procedure
Solutions of a certain class of fractional differintegral equations
AbstractRecently, several authors demonstrated the usefulness of fractional calculus in obtaining particular solutions of a number of such familiar second-order differential equations as those associated with Gauss, Legendre, Jacobi, Chebyshev, Coulomb, Whittaker, Euler, Hermite, and Weber equations. The main object of this paper is to show how some of the latest contributions on the subject by Tu et al. [1], involving the associated Legendre, Euler, and Hermite equations, can be presented in a unified manner by suitably appealing to a general theorem on particular solutions of a certain class of fractional differintegral equations
The interpretation of non-Markovian stochastic Schr\"odinger equations as a hidden-variable theory
Do diffusive non-Markovian stochastic Schr\"odinger equations (SSEs) for open
quantum systems have a physical interpretation? In a recent paper [Phys. Rev. A
66, 012108 (2002)] we investigated this question using the orthodox
interpretation of quantum mechanics. We found that the solution of a
non-Markovian SSE represents the state the system would be in at that time if a
measurement was performed on the environment at that time, and yielded a
particular result. However, the linking of solutions at different times to make
a trajectory is, we concluded, a fiction. In this paper we investigate this
question using the modal (hidden variable) interpretation of quantum mechanics.
We find that the noise function appearing in the non-Markovian SSE can
be interpreted as a hidden variable for the environment. That is, some chosen
property (beable) of the environment has a definite value even in the
absence of measurement on the environment. The non-Markovian SSE gives the
evolution of the state of the system ``conditioned'' on this environment hidden
variable. We present the theory for diffusive non-Markovian SSEs that have as
their Markovian limit SSEs corresponding to homodyne and heterodyne detection,
as well as one which has no Markovian limit.Comment: 9 page
A dual-mode mm-wave injection-locked frequency divider with greater than 18% locking range in 65nm CMOS
Only abstrac
Non-Markovian homodyne-mediated feedback on a two-level atom: a quantum trajectory treatment
Quantum feedback can stabilize a two-level atom against decoherence
(spontaneous emission), putting it into an arbitrary (specified) pure state.
This requires perfect homodyne detection of the atomic emission, and
instantaneous feedback. Inefficient detection was considered previously by two
of us. Here we allow for a non-zero delay time in the feedback circuit.
Because a two-level atom is a nonlinear optical system, an analytical solution
is not possible. However, quantum trajectories allow a simple numerical
simulation of the resulting non-Markovian process. We find the effect of the
time delay to be qualitatively similar to that of inefficient detection. The
solution of the non-Markovian quantum trajectory will not remain fixed, so that
the time-averaged state will be mixed, not pure. In the case where one tries to
stabilize the atom in the excited state, an approximate analytical solution to
the quantum trajectory is possible. The result, that the purity () of the average state is given by (where
is the spontaneous emission rate) is found to agree very well with the
numerical results.Comment: Changed content, Added references and Corrected typo
Invasive Allele Spread under Preemptive Competition
We study a discrete spatial model for invasive allele spread in which two
alleles compete preemptively, initially only the "residents" (weaker
competitors) being present. We find that the spread of the advantageous
mutation is well described by homogeneous nucleation; in particular, in large
systems the time-dependent global density of the resident allele is well
approximated by Avrami's law.Comment: Computer Simulation Studies in Condensed Matter Physics XVIII, edited
by D.P. Landau, S.P. Lewis, and H.-B. Schuttler, (Springer, Heidelberg,
Berlin, in press
Magnetic field effect on the dielectric constant of glasses: Evidence of disorder within tunneling barriers
The magnetic field dependence of the low frequency dielectric constant
(H) of a structural glass a - SiO2 + xCyHz was studied from 400 mK to 50
mK and for H up to 3T. Measurement of both the real and the imaginary parts of
is used to eliminate the difficult question of keeping constant the
temperature of the sample while increasing H: a non-zero (H) dependence is
reported in the same range as that one very recently reported on multicomponent
glasses. In addition to the recently proposed explanation based on
interactions, the reported (H) is interpreted quantitatively as a
consequence of the disorder lying within the nanometric barriers of the
elementary tunneling systems of the glass.Comment: latex Bcorrige1.tex, 5 files, 4 figures, 7 pages [SPEC-S02/009
Safety and reactogenicity of the 10-valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) co-administered with DTPa-HBV-IPV/Hib in Vietnamese infants
Quantum Kinetic Theory III: Quantum kinetic master equation for strongly condensed trapped systems
We extend quantum kinetic theory to deal with a strongly Bose-condensed
atomic vapor in a trap. The method assumes that the majority of the vapor is
not condensed, and acts as a bath of heat and atoms for the condensate. The
condensate is described by the particle number conserving Bogoliubov method
developed by one of the authors. We derive equations which describe the
fluctuations of particle number and phase, and the growth of the Bose-Einstein
condensate. The equilibrium state of the condensate is a mixture of states with
different numbers of particles and quasiparticles. It is not a quantum
superposition of states with different numbers of particles---nevertheless, the
stationary state exhibits the property of off-diagonal long range order, to the
extent that this concept makes sense in a tightly trapped condensate.Comment: 3 figures submitted to Physical Review
- …