143,647 research outputs found
Dynamics of a two-species Bose-Einstein condensate in a double well
We study the dynamics of a two-species Bose-Einstein condensate in a double
well. Such a system is characterized by the intraspecies and interspecies
s-wave scattering as well as the Josephson tunneling between the two wells and
the population transfer between the two species. We investigate the dynamics
for some interesting regimes and present numerical results to support our
conclusions. In the case of vanishing intraspecies scattering lengths and a
weak interspecies scattering length, we find collapses and revivals in the
population dynamics. A possible experimental implementation of our proposal is
briefly discussed.Comment: 7 pages, 5 figure
Observing collapse in two colliding dipolar Bose-Einstein condensates
We study the collision of two Bose-Einstein condensates with pure dipolar
interaction. A stationary pure dipolar condensate is known to be stable when
the atom number is below a critical value. However, collapse can occur during
the collision between two condensates due to local density fluctuations even if
the total atom number is only a fraction of the critical value. Using full
three-dimensional numerical simulations, we observe the collapse induced by
local density fluctuations. For the purpose of future experiments, we present
the time dependence of the density distribution, energy per particle and the
maximal density of the condensate. We also discuss the collapse time as a
function of the relative phase between the two condensates.Comment: 6 pages, 7 figure
Tidal wave in 102Pd: Rotating condensate of up to seven d-bosons
The yrast states of even even vibrational and transitional nuclei are inter-
preted as a rotating condensate of interacting d-bosons and the corresponding
semi-classical tidal wave concept. A simple experimental manifestation of the
anharmonicity caused by the boson interaction is found. The interpretation is
substantiated by calculations based on the Collective Model and the Cranking
Model.Comment: Proceedings of CGS1
Detection of a single-charge defect in a metal-oxide-semiconductor structure using vertically coupled Al and Si single-electron transistors
An Al-AlO_x-Al single-electron transistor (SET) acting as the gate of a
narrow (~ 100 nm) metal-oxide-semiconductor field-effect transistor (MOSFET)
can induce a vertically aligned Si SET at the Si/SiO_2 interface near the
MOSFET channel conductance threshold. By using such a vertically coupled Al and
Si SET system, we have detected a single-charge defect which is tunnel-coupled
to the Si SET. By solving a simple electrostatic model, the fractions of each
coupling capacitance associated with the defect are extracted. The results
reveal that the defect is not a large puddle or metal island, but its size is
rather small, corresponding to a sphere with a radius less than 1 nm. The small
size of the defect suggests it is most likely a single-charge trap at the
Si/SiO_2 interface. Based on the ratios of the coupling capacitances, the
interface trap is estimated to be about 20 nm away from the Si SET.Comment: 5 pages and 5 figure
Modelling psychological responses to the great East Japan earthquake and nuclear incident
This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits
unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited - Copyright @ 2012 Goodwin et al.This article has been made available through the Brunel Open Access Publishing Fund.The Great East Japan (Tōhoku/Kanto) earthquake of March 2011was followed by a major tsunami and nuclear incident. Several previous studies have suggested a number of psychological responses to such disasters. However, few previous studies have modelled individual differences in the risk perceptions of major events, or the implications of these perceptions for relevant behaviours. We conducted a survey specifically examining responses to the Great Japan earthquake and nuclear incident, with data collected 11-13 weeks following these events. 844 young respondents completed a questionnaire in three regions of Japan; Miyagi (close to the earthquake and leaking nuclear plants), Tokyo/Chiba (approximately 220 km from the nuclear plants), and Western Japan (Yamaguchi and Nagasaki, some 1000 km from the plants). Results indicated significant regional differences in risk perception, with greater concern over earthquake risks in Tokyo than in Miyagi or Western Japan. Structural equation analyses showed that shared normative concerns about earthquake and nuclear risks, conservation values, lack of trust in governmental advice about the nuclear hazard, and poor personal control over the nuclear incident were positively correlated with perceived earthquake and nuclear risks. These risk perceptions further predicted specific outcomes (e.g. modifying homes, avoiding going outside, contemplating leaving Japan). The strength and significance of these pathways varied by region. Mental health and practical implications of these findings are discussed in the light of the continuing uncertainties in Japan following the March 2011 events
An Analytic and Probabilistic Approach to the Problem of Matroid Representibility
We introduce various quantities that can be defined for an arbitrary matroid,
and show that certain conditions on these quantities imply that a matroid is
not representable over . Mostly, for a matroid of rank , we
examine the proportion of size- subsets that are dependent, and give
bounds, in terms of the cardinality of the matroid and a prime power, for
this proportion, below which the matroid is not representable over
. We also explore connections between the defined quantities and
demonstrate that they can be used to prove that random matrices have high
proportions of subsets of columns independent
Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSbTe
Substitution of Sb in FeSb by less than 0.5% of Te induces a transition
from a correlated semiconductor to an unconventional metal with large effective
charge carrier mass . Spanning the entire range of the semiconductor-metal
crossover, we observed an almost constant enhancement of the measured
thermopower compared to that estimated by the classical theory of electron
diffusion. Using the latter for a quantitative description one has to employ an
enhancement factor of 10-30. Our observations point to the importance of
electron-electron correlations in the thermal transport of FeSb, and
suggest a route to design thermoelectric materials for cryogenic applications.Comment: 3 pages, 3 figures, accepted for publication in Appl. Phys. Lett.
(2011
An quantum approach of measurement based on the Zurek's triple model
In a close form without referring the time-dependent Hamiltonian to the total
system, a consistent approach for quantum measurement is proposed based on
Zurek's triple model of quantum decoherence [W.Zurek, Phys. Rev. D 24, 1516
(1981)]. An exactly-solvable model based on the intracavity system is dealt
with in details to demonstrate the central idea in our approach: by peeling off
one collective variable of the measuring apparatus from its many degrees of
freedom, as the pointer of the apparatus, the collective variable de-couples
with the internal environment formed by the effective internal variables, but
still interacts with the measured system to form a triple entanglement among
the measured system, the pointer and the internal environment. As another
mechanism to cause decoherence, the uncertainty of relative phase and its
many-particle amplification can be summed up to an ideal entanglement or an
Shmidt decomposition with respect to the preferred basis.Comment: 22pages,3figure
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