1,691 research outputs found
Dynamical Casimir-Polder energy between an excited and a ground-state atom
We consider the Casimir-Polder interaction between two atoms, one in the
ground state and the other in its excited state. The interaction is
time-dependent for this system, because of the dynamical self-dressing and the
spontaneous decay of the excited atom. We calculate the dynamical
Casimir-Polder potential between the two atoms using an effective Hamiltonian
approach. The results obtained and their physical meaning are discussed and
compared with previous results based on a time-independent approach which uses
a non-normalizable dressed state for the excited atom.Comment: 11 page
Gender in the Construction Industry: Literature Review and Comparative Survey of Menâs and Womenâs Perceptions in UK Construction Consultancies
For more than two decades, construction industry leaders have made attempts to attract more women into professional roles to ease skills shortages and diversify the workforce. However, the number of women working in the industry has not improved significantly. This paper reviews previous literature on gender diversity in the construction industry and disseminates findings from a survey that investigated whether there are significant differences in self-perception between men and women in construction consultancies operating in the United Kingdom (UK). The survey questionnaire was completed by 60 men and 57 women. Analysis of the results confirmed that women tend to follow âzig-zagâ career development paths and that âglobal self-worthâ of women over the age of 40 is the lowest among all ages. However, little variation was found on initiatives to improve retention of women in construction consultancies. The results reveal that both men and women regarded improved flexible working-arrangements, transparent promotion criteria, return-to-work training, and outreach programs to schools the most crucial initiatives to retain women. This reinforces the call for organizations to introduce innovative strategic plans to change the masculine culture of the construction profession and modernize working practice away from the existing rather outdated traditional structure
Field fluctuations near a conducting plate and Casimir-Polder forces in the presence of boundary conditions
We consider vacuum fluctuations of the quantum electromagnetic field in the
presence of an infinite and perfectly conducting plate. We evaluate how the
change of vacuum fluctuations due to the plate modifies the Casimir-Polder
potential between two atoms placed near the plate. We use two different methods
to evaluate the Casimir-Polder potential in the presence of the plate. They
also give new insights on the role of boundary conditions in the Casimir-Polder
interatomic potential, as well as indications for possible generalizations to
more complicated boundary conditions.Comment: 10 page
Effect of boundaries on vacuum field fluctuations and radiation-mediated interactions between atoms
In this paper we discuss and review several aspects of the effect of boundary
conditions and structured environments on dispersion and resonance interactions
involving atoms or molecules, as well as on vacuum field fluctuations. We first
consider the case of a perfect mirror, which is free to move around an
equilibrium position and whose mechanical degrees of freedom are treated
quantum mechanically. We investigate how the quantum fluctuations of the
mirror's position affect vacuum field fluctuations for both a one-dimensional
scalar and electromagnetic field, showing that the effect is particularly
significant in the proximity of the moving mirror. This result can be also
relevant for possible gravitational effects, since the field energy density
couples to gravity. We stress that this interaction-induced modification of the
vacuum field fluctuations can be probed through the Casimir-Polder interaction
with a polarizable body, thus allowing to detect the effect of the mirror's
quantum position fluctuations. We then consider the effect of an environment
such as an isotropic photonic crystal or a metallic waveguide, on the resonance
interaction between two entangled identical atoms, one excited and the other in
the ground state. We discuss the strong dependence of the resonance interaction
with the relative position of the atomic transition frequency with the gap of
the photonic crystal in the former case, and with the cut-off frequency of
waveguide in the latter.Comment: 8 pages, 2 figures, Proceedings of the Eighth International Workshop
DICE 2016 Spacetime - Matter - Quantum Mechanic
Testing the gamma-ray burst variability/peak luminosity correlation on a Swift homogeneous sample
We test the gamma-ray burst correlation between temporal variability and peak
luminosity of the -ray profile on a homogeneous sample of 36 Swift/BAT
GRBs with firm redshift determination. This is the first time that this
correlation can be tested on a homogeneous data sample. The correlation is
confirmed, as long as the 6 GRBs with low luminosity (<5x10^{50} erg s^{-1} in
the rest-frame 100-1000 keV energy band) are ignored. We confirm that the
considerable scatter of the correlation already known is not due to the
combination of data from different instruments with different energy bands, but
it is intrinsic to the correlation itself. Thanks to the unprecedented
sensitivity of Swift/BAT, the variability/peak luminosity correlation is tested
on low-luminosity GRBs. Our results show that these GRBs are definite outliers.Comment: Accepted for Publication in MNRAS. 10 pages, 5 figures, 3 table
Validation of an Emission Model for a Marine Diesel Engine with Data from Sea Operations
In this study, a model is developed to simulate the dynamics of an internal combustion engine, and it is calibrated and validated against reliable experimental data, making it a tool that can effectively be adopted to conduct emission predictions. In this work, the Ricardo WAVE software is applied to the simulation of a particular marine diesel engine, a four-stroke engine used in the maritime field. Results from the bench tests are used for the calibration of the model. Finally, the calibration of the model and its validation with full-scale data measured at sea are presented. The prediction includes not only the classic engine operating parameters for a comparison with surveys but also an estimate of nitrogen oxide emissions, which are compared with similar results obtained with emission factors. The calibration of the model made it possible to obtain an overlap between the simulation results and real data with an average error of approximately 7% on power, torque, and consumption. The model provides encouraging results, suggesting further applications, such as in the study on transient conditions, coupling of the engine model with the ship model for a complete simulation of the operating conditions, and optimization studies on consumption and emissions. The availability of the emission data during the sea trial and validated simulation results are the strengths and novelties of this work
Are Swift gamma-ray bursts consistent with the Ghirlanda relation?
A few tight correlations linking several properties of gamma-ray bursts
(GRBs), namely the spectral peak energy, the total radiated energy, and the
afterglow break time, have been discovered with pre-Swift GRBs. They were used
to constrain the cosmological parameters, together with type-Ia supernovae.
However, the tightness of these correlations is a challenge to GRB models. We
explore the effect of adding Swift bursts to the Ghirlanda and Liang-Zhang
relations. Although they are both still valid, they become somewhat weakened
mostly due to the presence of significant outliers, which otherwise are
apparently normal GRBs so difficult to distinguish. The increased dispersion of
the relations makes them less reliable for purposes of precision cosmology.Comment: Paper accepted for publication on A&A (7 pages, 2 figures). Small
changes after comment
Nonlocal field correlations and dynamical Casimir-Polder forces between one excited- and two ground-state atoms
The problem of nonlocality in the dynamical three-body Casimir-Polder
interaction between an initially excited and two ground-state atoms is
considered. It is shown that the nonlocal spatial correlations of the field
emitted by the excited atom during the initial part of its spontaneous decay
may become manifest in the three-body interaction. The observability of this
new phenomenon is discussed.Comment: 17 pages, 1 figure, sub. to Phys. Rev.
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