129 research outputs found
Time-dependent Casimir-Polder forces and partially dressed states
A time-dependent Casimir-Polder force is shown to arise during the time
evolution of a partially dressed two-level atom. The partially dressed atom is
obtained by a rapid change of an atomic parameter such as its transition
frequency, due to the action of some external agent. The electromagnetic field
fluctuations around the atom, averaged over the solid angle for simplicity, are
calculated as a function of time, and it is shown that the interaction energy
with a second atom yields a dynamical Casimir-Polder potential between the two
atoms
Thermal and non-thermal signatures of the Unruh effect in Casimir-Polder forces
We show that Casimir-Polder forces between two relativistic uniformly
accelerated atoms exhibit a transition from the short distance thermal-like
behavior predicted by the Unruh effect, to a long distance non-thermal
behavior, associated with the breakdown of a local inertial description of the
system. This phenomenology extends the Unruh thermal response detected by a
single accelerated observer to an accelerated spatially extended system of two
particles, and we identify the characteristic length scale for this crossover
with the inverse of the proper acceleration of the two atoms. Our results are
derived separating at fourth order in perturbation theory the contributions of
vacuum fluctuations and radiation reaction field to the Casimir-Polder
interaction between two atoms moving in two generic stationary trajectories
separated by a constant distance, and linearly coupled to a scalar field. The
field can be assumed in its vacuum state or at finite temperature, resulting in
a general method for the computation of Casimir-Polder forces in stationary
regimes.Comment: 6 pages, 1 figure. Revised versio
Nonlocal properties of dynamical three-body Casimir-Polder forces
We consider the three-body Casimir-Polder interaction between three atoms
during their dynamical self-dressing. We show that the time-dependent
three-body Casimir-Polder interaction energy displays nonlocal features related
to quantum properties of the electromagnetic field and to the nonlocality of
spatial field correlations. We discuss the measurability of this intriguing
phenomenon and its relation with the usual concept of stationary three-body
forces.Comment: 4 page
The Affect of Globalization on Terrorism
This thesis proposal will dive into the concept of terrorism and how it is an act of force and has proven to be detrimental to the modern world. In addition, this thesis will analyze the concept of terrorism as well as the rationale behind it. It is important to understand and study this as terrorism is a complex entity made up of different themes. The concentration of this thesis will highlight how globalization has affected the phenomena of terrorism in the past, present, and ultimately the future. Globalization and terrorism have a relationship that many scholars and researchers have noticed. Historical events as well as data patterns have proved this to be accurate as well. Terrorism is a phenomenon that has been around for centuries, taking different forms as it has evolved. Due to gradual change, terrorist groups organize their attacks based on ideologies primarily. It is at the forefront of problems not only the United States faces, but the world too. This concept has spread across the world causing fear and chaos to innocent civilians. This gradual change that has changed the dynamic of terrorism is globalization. Globalization has allowed for many exchanges between people around the world. These exchanges include people, goods, ideologies, religion, etc. Based on this claim, it can be inferred that globalization has provided a positive outcome to the world by bringing together countries and people. However, it is crucial to note that while many people have felt globalization has benefited them, there are many people around the world that have felt threatened by the spread of this concept. Globalization has benefited heinous acts like terrorism through involvement of modern technologies. My thesis statement is “Globalization has affected terrorism in the way it has made terrorism easier, more accessible, and has impacted the frequency in which attacks occur.” The iv findings provided in the literature review and data analysis support the evidence that globalization does impact terrorism through different factors that affect countries daily. In other words, is there a significant relationship between globalization factors and rates of terrorism globally
Spatial correlations of vacuum fluctuations and the Casimir-Polder potential
We calculate the Casimir-Polder intermolecular potential using an effective
Hamiltonian recently introduced. We show that the potential can be expressed in
terms of the dynamical polarizabilities of the two atoms and the equal-time
spatial correlation of the electric field in the vacuum state. This gives
support to an interesting physical model recently proposed in the literature,
where the potential is obtained from the classical interaction between the
instantaneous atomic dipoles induced and correlated by the vacuum fluctuations.
Also, the results obtained suggest a more general validity of this intuitive
model, for example when external boundaries or thermal fields are present.Comment: 7 page
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
Tuning the collective decay of two entangled emitters by means of a nearby surface
We consider the radiative properties of a system of two identical correlated
atoms interacting with the electromagnetic field in its vacuum state in the
presence of a generic dielectric environment. We suppose that the two emitters
are prepared in a symmetric or antisymmetric superposition of one ground state
and one excited state and we evaluate the transition rate to the collective
ground state, showing distinctive cooperative radiative features. Using a
macroscopic quantum electrodynamics approach to describe the electromagnetic
field, we first obtain an analytical expression for the decay rate of the two
entangled two-level atoms in terms of the Green's tensor of the generic
external environment. We then investigate the emission process when both atoms
are in free space and subsequently when a perfectly reflecting mirror is
present, showing how the boundary affects the physical features of the
superradiant and subradiant emission by the two coupled emitters. The
possibility to control and tailor radiative processes is also discussed.Comment: 11 pages, 8 figure
Casimir-Polder potentials as entanglement probe
We have considered the interaction of a pair of spatially separated two-level
atoms with the electromagnetic field in its vacuum state and we have analyzed
the amount of entanglement induced between the two atoms by the non local field
fluctuations. This has allowed us to characterize the quantum nature of the non
local correlations of the electromagnetic field vacuum state as well as to link
the induced quantum entanglement with Casimir-Polder potentials.Comment: Published on Europhysics Letters 78 (2007) 3000
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