2,236 research outputs found
Observation of Exceptional Points in Electronic Circuits
Two damped coupled oscillators have been used to demonstrate the occurrence
of exceptional points in a purely classical system. The implementation was
achieved with electronic circuits in the kHz-range. The experimental results
perfectly match the mathematical predictions at the exceptional point. A
discussion about the universal occurrence of exceptional points -- connecting
dissipation with spatial orientation -- concludes the paper.Comment: 4 pages, latex, 3 postscript figures, submitted for publicatio
Chaos in Axially Symmetric Potentials with Octupole Deformation
Classical and quantum mechanical results are reported for the single particle
motion in a harmonic oscillator potential which is characterized by a
quadrupole deformation and an additional octupole deformation. The chaotic
character of the motion is srongly dependent on the quadrupole deformation in
that for a prolate deformation virtually no chaos is discernible while for the
oblate case the motion shows strong chaos when the octupole term is turned on.Comment: 6 pages LaTex plus 4 figures available by contacting the authors
directly, published in PHYS.REV.LETT. 72(1994) 235
The economic value of remote sensing by satellite: An ERTS overview and the value of continuity of service. Volume 2: Source document
The economic value of an ERS system with a technical capability similar to ERTS, allowing for increased coverage obtained through the use of multiple active satellites in orbit is presented. A detailed breakdown of the benefits achievable from an ERS system is given and a methodology for their estimation is established. The ECON case studies in agriculture, water use, and land cover are described along with the current ERTS system. The cost for a projected ERS system is given
United States benefits of improved worldwide wheat crop information from a LANDSAT system
The value of worldwide information improvements on wheat crops, promised by LANDSAT, is measured in the context of world wheat markets. These benefits are based on current LANDSAT technical goals and assume that information is made available to all (United States and other countries) at the same time. A detailed empirical sample demonstration of the effect of improved information is given; the history of wheat commodity prices for 1971-72 is reconstructed and the price changes from improved vs. historical information are compared. The improved crop forecasting from a LANDSAT system assumed include wheat crop estimates of 90 percent accuracy for each major wheat producing region. Accurate, objective worldwide wheat crop information using space systems may have a very stabilizing influence on world commodity markets, in part making possible the establishment of long-term, stable trade relationships
Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dots
We report on the development and testing of a coplanar stripline antenna that
is designed for integration in a magneto-photoluminescence experiment to allow
coherent control of individual electron spins confined in single self-assembled
semiconductor quantum dots. We discuss the design criteria for such a structure
which is multi-functional in the sense that it serves not only as microwave
delivery but also as electrical top gate and shadow mask for the single quantum
dot spectroscopy. We present test measurements on hydrogenated amorphous
silicon, demonstrating electrically detected magnetic resonance using the
in-plane component of the oscillating magnetic field created by the coplanar
stripline antenna necessary due to the particular geometry of the quantum dot
spectroscopy. From reference measurements using a commercial electron spin
resonance setup in combination with finite element calculations simulating the
field distribution in the structure, we obtain an average magnetic field of
~0.2mT at the position where the quantum dots would be integrated into the
device. The corresponding pi-pulse time of ~0.3us fully meets the requirements
set by the high sensitivity optical spin read-out scheme developed for the
quantum dot
Statistical Fluctuations of Electromagnetic Transition Intensities in pf-Shell Nuclei
We study the fluctuation properties of E2 and M1 transition intensities among
T=0,1 states of A = 60 nuclei in the framework of the interacting shell model,
using a realistic effective interaction for pf-shell nuclei with a Ni56 as a
core. It is found that the B(E2) distributions are well described by the
Gaussian orthogonal ensemble of random matrices (Porter-Thomas distribution)
independently of the isobaric quantum number T_z. However, the statistics of
the B(M1) transitions is sensitive to T_z: T_z=1 nuclei exhibit a Porter-Thomas
distribution, while a significant deviation from the GOE statistics is observed
for self-conjugate nuclei (T_z=0).Comment: 8 pages, latex, 3 figures (ps format
Large N Scaling Behavior of the Lipkin-Meshkov-Glick Model
We introduce a novel semiclassical approach to the Lipkin model. In this way
the well-known phase transition arising at the critical value of the coupling
is intuitively understood. New results -- showing for strong couplings the
existence of a threshold energy which separates deformed from undeformed states
as well as the divergence of the density of states at the threshold energy --
are explained straightforwardly and in quantitative terms by the appearance of
a double well structure in a classical system corresponding to the Lipkin
model. Previously unnoticed features of the eigenstates near the threshold
energy are also predicted and found to hold.Comment: 4 pages, 2 figures, to appear in PR
Excited state quantum phase transitions in many-body systems
Phenomena analogous to ground state quantum phase transitions have recently
been noted to occur among states throughout the excitation spectra of certain
many-body models. These excited state phase transitions are manifested as
simultaneous singularities in the eigenvalue spectrum (including the gap or
level density), order parameters, and wave function properties. In this
article, the characteristics of excited state quantum phase transitions are
investigated. The finite-size scaling behavior is determined at the mean field
level. It is found that excited state quantum phase transitions are universal
to two-level bosonic and fermionic models with pairing interactions.Comment: LaTeX (elsart), 37 pages; to be published in Ann. Phys. (N.Y.
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