4,058 research outputs found
Ehrenfest Dynamics and Frictionless Cooling Methods
Recently introduced methods which result in shortcuts to adiabaticity,
particularly in the context of frictionless cooling, are rederived and
discussed in the framework of an approach based on Ehrenfest dynamics. This
construction provides physical insights into the emergence of the Ermakov
equation, the choice of its boundary conditions, and the use of minimum
uncertainty states as indicators of the efficiency of the procedure.
Additionally, it facilitates the extension of frictionless cooling to more
general situations of physical relevance, such as optical dipole trapping
schemes. In this context, we discuss frictionless cooling in the short-time
limit, a complementary case to the one considered in the literature, making
explicit the limitations intrinsic to the technique when the full
three-dimensional case is analyzed.Comment: 9 pages, 4 figures, v2: To appear in Physical Review A. (some minor
typos corrected and some references added
Squeezing and robustness of frictionless cooling strategies
Quantum control strategies that provide shortcuts to adiabaticity are
increasingly considered in various contexts including atomic cooling. Recent
studies have emphasized practical issues in order to reduce the gap between the
idealized models and actual ongoing implementations. We rephrase here the
cooling features in terms of a peculiar squeezing effect, and use it to
parametrize the robustness of frictionless cooling techniques with respect to
noise-induced deviations from the ideal time-dependent trajectory for the
trapping frequency. We finally discuss qualitative issues for the experimental
implementation of this scheme using bichromatic optical traps and lattices,
which seem especially suitable for cooling Fermi-Bose mixtures and for
investigating equilibration of negative temperature states, respectively.Comment: 9 pages, 7 figures; To appear in Physical Review
Fragility of the Commons under Prospect-Theoretic Risk Attitudes
We study a common-pool resource game where the resource experiences failure
with a probability that grows with the aggregate investment in the resource. To
capture decision making under such uncertainty, we model each player's risk
preference according to the value function from prospect theory. We show the
existence and uniqueness of a pure Nash equilibrium when the players have
heterogeneous risk preferences and under certain assumptions on the rate of
return and failure probability of the resource. Greater competition, vis-a-vis
the number of players, increases the failure probability at the Nash
equilibrium; we quantify this effect by obtaining bounds on the ratio of the
failure probability at the Nash equilibrium to the failure probability under
investment by a single user. We further show that heterogeneity in attitudes
towards loss aversion leads to higher failure probability of the resource at
the equilibrium.Comment: Accepted for publication in Games and Economic Behavior, 201
Frequency and time profiles of metric wave isolated Type I solar noise storm bursts at high spectral and temporal resolution
Type I noise storms constitute a sizeable faction of the active-Sun radio
emission component. Observations of isolated instances of such bursts, in the
swept-frequency-mode at metric wavelengths, have remained sparse, with several
unfilled regions in the frequency coverage. Dynamic spectra of the burst
radiation, in the 30 - 130 MHz band, obtained from the recently commissioned
digital High Resolution Spectrograph (HRS) at the Gauribidanur Radio
Observatory, on account of the superior frequency and time resolution, have
unravelled in explicit detail the temporal and spectral profiles of isolated
bursts. Apart from presenting details on their fundamental emission features,
the time and frequency profile symmetry, with reference to custom-specific
Gaussian distributions, has been chosen as the nodal criterion to statistically
explain the state of the source regions in the vicinity of magnetic
reconnections, the latent excitation agent that contributes to plasma wave
energetics, and the quenching phenomenon that causes damping of the burst
emission.Comment: 9 pages 7 black and white / grey-scale figures (inclusive of 3
composite). MNRAS - accepte
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