2,137 research outputs found
Spontaneous emission of an atom near an oscillating mirror
We investigate the spontaneous emission of one atom placed near an oscillating reflecting plate. We consider the atom modeled as a two-level system, interacting with the quantum electromagnetic field in the vacuum state, in the presence of the oscillating mirror. We suppose that the plate oscillates adiabatically, so that the time-dependence of the interaction Hamiltonian is entirely enclosed in the time-dependent mode functions, satisfying the boundary conditions at the plate surface, at any given time. Using time-dependent perturbation theory, we evaluate the transition rate to the ground-state of the atom, and show that it depends on the time-dependent atom-plate distance. We also show that the presence of the oscillating mirror significantly affects the physical features of the spontaneous emission of the atom, in particular the spectrum of the emitted radiation. Specifically, we find the appearance of two symmetric lateral peaks in the spectrum, not present in the case of a static mirror, due to the modulated environment. The two lateral peaks are separated from the central peak by the modulation frequency, and we discuss the possibility to observe them with actual experimental techniques of dynamical mirrors and atomic trapping. Our results indicate that a dynamical (i.e., time-modulated) environment can give new possibilities to control and manipulate also other radiative processes of two or more atoms or molecules nearby, for example their cooperative decay or the resonant energy transfer
Vacuum field correlations and three-body Casimir-Polder potential with one excited atom
The three-body Casimir-Polder potential between one excited and two
ground-state atoms is evaluated. A physical model based on the dressed field
correlations of vacuum fluctuations is used, generalizing a model previously
introduced for three ground-state atoms. Although the three-body potential with
one excited atom is already known in the literature, our model gives new
insights on the nature of non-additive Casimir-Polder forces with one or more
excited atoms.Comment: 9 page
Voices from the Coolest Corner of Hell: A Content Analysis of Slave Narratives in the Study of Creolization in the Education of 19th Century African American Slaves
The general argument made by Southern historian, Ulrich Bonnell Phillips in 1918, is that the plantation functioned as a type of school for the slave. Similarly, in 1976, Anthony Gerald Albanese examined the plantation system as an institution that conditioned the behaviors of both slaves and slave owners. I maintain that the plantation system was not only an educative agency that conditioned behaviors, but also a conduit for the creolization process. The focus of this study is creolization in the education of African American slaves in the nineteenth century. This is a mixed methods content analysis of African American slave narratives. I use Michel-Rolph Trouillot’s plantation context heuristic to help conceptualize the creolization process that I believe is present within the text. Within the qualitative strand of the sequential mixed method design, I identify thematic codes that signify pedagogy and creolization theory. I classify these codes into three families: slave-making strategies (SMS) codes, creolization theory (CT) codes, and education and literacy (EL) codes. The coding units I collect during the qualitative phase of this study will make up the dataset for the quantitative phase of research in which I explore the relationships among coding families
Nonequilibrium dressing in a cavity with a movable reflecting mirror
We consider a movable mirror coupled to a one-dimensional massless scalar
field in a cavity. Both the field and the mirror's mechanical degrees of
freedom are described quantum-mechanically, and they can interact each other
via the radiation pressure operator. We investigate the dynamical evolution of
mirror and field starting from a nonequilibrium initial state, and their local
interaction which brings the system to a stationary configuration for long
times. This allows us to study the time-dependent dressing process of the
movable mirror interacting with the field, and its dynamics leading to a local
equilibrium dressed configuration. Also, in order to explore the effect of the
radiation pressure on both sides of the movable mirror, we generalize the
effective field-mirror Hamiltonian and previous results to the case of two
cavities sharing the same mobile boundary. This leads us to address, in the
appropriate limit, the dynamical dressing problem of a single mobile wall,
bounded by a harmonic potential, in the vacuum space.Comment: 10 pages, 4 figure
Van der Waals and resonance interactions between accelerated atoms in vacuum and the Unruh effect
We discuss different physical effects related to the uniform acceleration of
atoms in vacuum, in the framework of quantum electrodynamics. We first
investigate the van der Waals/Casimir-Polder dispersion and resonance
interactions between two uniformly accelerated atoms in vacuum. We show that
the atomic acceleration significantly affects the van der Waals force, yielding
a different scaling of the interaction with the interatomic distance and an
explicit time dependence of the interaction energy. We argue how these results
could allow for an indirect detection of the Unruh effect through dispersion
interactions between atoms. We then consider the resonance interaction between
two accelerated atoms, prepared in a correlated Bell-type state, and
interacting with the electromagnetic field in the vacuum state, separating
vacuum fluctuations and radiation reaction contributions, both in the
free-space and in the presence of a perfectly reflecting plate. We show that
nonthermal effects of acceleration manifest in the resonance interaction,
yielding a change of the distance dependence of the resonance interaction
energy. This suggests that the equivalence between temperature and acceleration
does not apply to all radiative properties of accelerated atoms. To further
explore this aspect, we evaluate the resonance interaction between two atoms in
non inertial motion in the coaccelerated (Rindler) frame and show that in this
case the assumption of an Unruh temperature for the field is not required for a
complete equivalence of locally inertial and coaccelerated points of views.Comment: 8 pages, Proceedings of the Eighth International Workshop DICE 2016
Spacetime - Matter - Quantum Mechanic
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New Insights into the Charge-Transfer-to-Solvent Spectrum of Aqueous Iodide: Surface versus Bulk.
Liquid phase charge-transfer-to-solvent (CTTS) transitions are important, as they serve as photochemical routes to solvated electrons. In this work, broadband deep-ultraviolet electronic sum frequency generation (DUV-ESFG) and two-photon absorption (2PA) spectroscopic techniques were used to assign and compare the nature of the aqueous iodide CTTS excitations at the air/water interface and in bulk solution. In the one-photon absorption (1PA) spectrum, excitation to the 6s Rydberg-like orbital (5p → 6s) gives rise to a pair of spin-orbit split iodine states, 2P3/2 and 2P1/2. In the 2PA spectra, the lower-energy 2P3/2 peak is absent and the observed 2PA peak, which is ∼0.14 eV blue-shifted relative to the upper 2P1/2 CTTS peak seen in 1PA, arises from 5p → 6p electronic promotion. The band observed in the ESFG spectrum is attributed to mixing of excited states involving 5p → 6p and 5p → 6s promotions caused by both vibronic coupling and the external electric field generated by asymmetric interfacial solvation
WISE Circumstellar Disks in the Young Sco-Cen Association
We present an analysis of the WISE photometric data for 829 stars in the
Sco-Cen OB2 association, using the latest high-mass membership probabilities.
We detect infrared excesses associated with 135 BAF-type stars, 99 of which are
secure Sco-Cen members. There is a clear increase in excess fraction with
membership probability, which can be fitted linearly. We infer that 41+-5% of
Sco-Cen OB2 BAF stars to have excesses, while the field star excess fraction is
consistent with zero. This is the first time that the probability of
non-membership has been used in the calculation of excess fractions for young
stars. We do not observe any significant change in excess fraction between the
three subgroups. Within our sample, we have observed that B-type association
members have a significantly smaller excess fraction than A and F-type
association members.Comment: 5 Pages, 3 figure, 4 tables. Complete table 1 included. Accepted to
MNRAS Letter
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