57,828 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
The Environmental Contribution to Wayfinding in Museums: Enhancement and Usage by Controlling Flows and Paths
The field of research in which wayfinding is situated refers to the way people move in reaction to environmental stimulation. It therefore fully concerns not just signage but also space designing, its geometric configuration, technical solutions and their material characterization. The focus is consequently on environmental factors that facilitate wayfinding in a museum (accessibility, visibility, etc.) and on other elements such as spatial configuration, architectural features and functional aspects. These factors influence relational phenomena and therefore visitors’ satisfaction. Methods and tools for designing and managing spaces have been studied in the research. The configurational analysis method of space has been used to objectify syntactic features of space. In particular, the outcomes of an experimental project, which have been analyzed in a master’s thesis on the re-functionalization of the museum of Palazzo dei Diamanti in Ferrara, are presented. Permeability, proximity, connections of spaces, namely meaningful features to ensure wayfinding have been examined. Space parameters resulting from the geometry of the layout, from the visual connections and from the changes of direction were then evaluated. The outcomes have been used as inputs for designing a unitary tour route circuit, that also reconnects the museum’s second floor, and for planning three independent alternative routes for a differentiated use of the museum
Raman spectra of GexAsySe1−x−y glasses
Various Ge–As–Se glasses spanning a mean coordination number (MCN) from 2.2 to 2.94 have been investigated using differential scanning calorimetry and Raman spectroscopy. The glass transition temperature Tg was found to increase with increasing MCN, except for those glasses located within the nanoscale phase-separated region of the phase diagram. The evolution of Raman features at wavenumbers from 150 to 350 cm⁻¹ exhibits two transitionlike features. Merging of the 225 and 250 cm⁻¹ modes at MCN=2.5 is a symbol of the extinction of Se–Se bonds. Additionally, the appearance of two modes at 280–290 and 170 cm⁻¹ at MCN>2.7 come from the defect modes of ethanelike Ge₂Se₆/₂. The increase in the scattering from these defects is an important factor leading to enhanced optical loss in the glasses with high MCN.This research was partly supported by the Australian
Research Council through its Centres of Excellence and Federation
Fellow Programs
First axion dark matter search with toroidal geometry
We firstly report an axion haloscope search with toroidal geometry. In this
pioneering search, we exclude the axion-photon coupling
down to about GeV over the axion mass range from 24.7
to 29.1 eV at a 95\% confidence level. The prospects for axion dark matter
searches with larger scale toroidal geometry are also considered.Comment: 5 pages, 5 figures, 1 table and to appear in PRD-R
Imprinting a complete information about a quantum channel on its output state
We introduce a novel property of bipartite quantum states, which we call
"faithfulness", and we say that a state is faithful when acting with a channel
on one of the two quantum systems, the output state carries a complete
information about the channel. The concept of faithfulness can also be extended
to sets of states, when the output states patched together carry a complete
imprinting of the channel.Comment: revtex4, 4 pages, submitted to PR
Construction of equilibrium networks with an energy function
We construct equilibrium networks by introducing an energy function depending
on the degree of each node as well as the product of neighboring degrees. With
this topological energy function, networks constitute a canonical ensemble,
which follows the Boltzmann distribution for given temperature. It is observed
that the system undergoes a topological phase transition from a random network
to a star or a fully-connected network as the temperature is lowered. Both
mean-field analysis and numerical simulations reveal strong first-order phase
transitions at temperatures which decrease logarithmically with the system
size. Quantitative discrepancies of the simulation results from the mean-field
prediction are discussed in view of the strong first-order nature.Comment: To appear in J. Phys.
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