14,167 research outputs found
Induced Coherence and Stable Soliton Spiraling
We develop a theory of soliton spiraling in a bulk nonlinear medium and
reveal a new physical mechanism: periodic power exchange via induced coherence,
which can lead to stable spiraling and the formation of dynamical two-soliton
states. Our theory not only explains earlier observations, but provides a
number of predictions which are also verified experimentally. Finally, we show
theoretically and experimentally that soliton spiraling can be controled by the
degree of mutual initial coherence.Comment: 4 pages, 5 figure
GEMINI: A Generic Multi-Modal Natural Interface Framework for Videogames
In recent years videogame companies have recognized the role of player
engagement as a major factor in user experience and enjoyment. This encouraged
a greater investment in new types of game controllers such as the WiiMote, Rock
Band instruments and the Kinect. However, the native software of these
controllers was not originally designed to be used in other game applications.
This work addresses this issue by building a middleware framework, which maps
body poses or voice commands to actions in any game. This not only warrants a
more natural and customized user-experience but it also defines an
interoperable virtual controller. In this version of the framework, body poses
and voice commands are respectively recognized through the Kinect's built-in
cameras and microphones. The acquired data is then translated into the native
interaction scheme in real time using a lightweight method based on spatial
restrictions. The system is also prepared to use Nintendo's Wiimote as an
auxiliary and unobtrusive gamepad for physically or verbally impractical
commands. System validation was performed by analyzing the performance of
certain tasks and examining user reports. Both confirmed this approach as a
practical and alluring alternative to the game's native interaction scheme. In
sum, this framework provides a game-controlling tool that is totally
customizable and very flexible, thus expanding the market of game consumers.Comment: WorldCIST'13 Internacional Conferenc
Complete Set of Homogeneous Isotropic Analytic Solutions in Scalar-Tensor Cosmology with Radiation and Curvature
We study a model of a scalar field minimally coupled to gravity, with a
specific potential energy for the scalar field, and include curvature and
radiation as two additional parameters. Our goal is to obtain analytically the
complete set of configurations of a homogeneous and isotropic universe as a
function of time. This leads to a geodesically complete description of the
universe, including the passage through the cosmological singularities, at the
classical level. We give all the solutions analytically without any
restrictions on the parameter space of the model or initial values of the
fields. We find that for generic solutions the universe goes through a singular
(zero-size) bounce by entering a period of antigravity at each big crunch and
exiting from it at the following big bang. This happens cyclically again and
again without violating the null energy condition. There is a special subset of
geodesically complete non-generic solutions which perform zero-size bounces
without ever entering the antigravity regime in all cycles. For these, initial
values of the fields are synchronized and quantized but the parameters of the
model are not restricted. There is also a subset of spatial curvature-induced
solutions that have finite-size bounces in the gravity regime and never enter
the antigravity phase. These exist only within a small continuous domain of
parameter space without fine tuning initial conditions. To obtain these
results, we identified 25 regions of a 6-parameter space in which the complete
set of analytic solutions are explicitly obtained.Comment: 38 pages, 29 figure
Batalin-Vilkovisky Integrals in Finite Dimensions
The Batalin-Vilkovisky method (BV) is the most powerful method to analyze
functional integrals with (infinite-dimensional) gauge symmetries presently
known. It has been invented to fix gauges associated with symmetries that do
not close off-shell. Homological Perturbation Theory is introduced and used to
develop the integration theory behind BV and to describe the BV quantization of
a Lagrangian system with symmetries. Localization (illustrated in terms of
Duistermaat-Heckman localization) as well as anomalous symmetries are discussed
in the framework of BV.Comment: 35 page
Approximate dynamical symmetry of hydrogen atoms in circularly polarized microwave fields
This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevA.50.5077.We report the discovery of an integrable three-dimensional Hamiltonian system with a velocity-dependent potential. A two-dimensional restriction of that system is (for low frequencies) a good approximation of the motion (in the polarization plane) of the hydrogen atom in circularly polarized microwave fields. An additional integral of motion of the integrable two-dimensional system (being approximate invariant for the hydrogen atom in a circular field) is used in the calculation of the classical ionization field threshold. The result is consistent with all available experimental observations
Hydrogen atoms in circularly polarized microwave fields: Near-integrability and ionization
This is the published version, also available here: http://dx.doi.org/10.1103/PhysRevA.52.1358.We have recently found that the hydrogen atom in a circularly polarized (CP) microwave field possesses an approximate dynamical symmetry and its bounded motion can be well described by a three-dimensional integrable (but nonseparable) Hamiltonian function with a velocity-dependent potential [Raković and Chu, Phys. Rev. A 50, 5077 (1994)]. This finding provides a theoretical foundation for the understanding of the origin of the regularity of Rydberg atom dynamics in CP fields. We describe here the phase space topology of the three-dimensional integrable system relevant to the microwave ionization of the hydrogen atoms in CP fields. Using the integrable system as an approximation to the real system and with the use of the two additional integrals of motion, we are able to trace the deformation of the tori up to the point of bifurcation (ionization). From this, we have determined the classical ionization-field threshold law fth≊1/cn40, where n0 is the principal quantum number of the initial state of the hydrogen atom and c is almost a constant (≊6 a.u.). These results are in good accord with the existing experimental observations
Diffusion due to the Beam-Beam Interaction and Fluctuating Fields in Hadron Colliders
Random fluctuations in the tune, beam offsets and beam size in the presence
of the beam-beam interaction are shown to lead to significant particle
diffusion and emittance growth in hadron colliders. We find that far from
resonances high frequency noise causes the most diffusion while near resonances
low frequency noise is responsible for the large emittance growth observed.
Comparison of different fluctuations shows that offset fluctuations between the
beams causes the largest diffusion for particles in the beam core.Comment: 5 pages, 3 postscript figure
New high-efficiency source of photon pairs for engineering quantum entanglement
We have constructed an efficient source of photon pairs using a
waveguide-type nonlinear device and performed a two-photon interference
experiment with an unbalanced Michelson interferometer. Parametric
down-converted photons from the nonlinear device are detected by two detectors
located at the output ports of the interferometer. Because the interferometer
is constructed with two optical paths of different length, photons from the
shorter path arrive at the detector earlier than those from the longer path. We
find that the difference of arrival time and the time window of the coincidence
counter are important parameters which determine the boundary between the
classical and quantum regime. When the time window of the coincidence counter
is smaller than the arrival time difference, fringes of high visibility
(80 10%) were observed. This result is only explained by quantum theory
and is clear evidence for quantum entanglement of the interferometer's optical
paths.Comment: 4 pages, 4 figures, IQEC200
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