AnomalousAnomalous AharonovBohmAharonovBohm gapgap
Marini, Andrea
currents #12;The AB effect in carbon nano-tubes (CNTs) A. Bachtold et al., Nature 397, 673 (1999) S. Zaric is increased... ...consistently with a gap flux dependence #12;The AB effect in carbon nano-tubes (CNTs) AAnomalousAnomalous AharonovBohmAharonovBohm gapgap oscillations inoscillations in carbon
Does the Aharonov–Bohm Effect Exist?
Timothy H. Boyer
2000-01-01
We draw a distinction between the Aharonov–Bohm phase shift and the Aharonov–Bohm effect. Although the Aharonov–Bohm phase shift occurring when an electron beam passes around a magnetic solenoid is well-verified experimentally, it is not clear whether this phase shift occurs because of classical forces or because of a topological effect occurring in the absence of classical forces as claimed by
Aharonov-Bohm Effect in Synchrotron Radiation
Bagrov, V G; Levin, A; Tlyachev, V B
2001-01-01
Synchrotron radiation of a charged particle in a constant uniform magnetic field and in the presence of the Aharonov-Bohm solenoid field is studied in the frame of the relativistic quantum theory. First, to this end exact solutions of the Klein-Gordon and Dirac equations are found. Using such solutions, all characteristics of one photon spontaneous irradiation, such as its intensity and angular distribution and polarization were calculated and analyzed. It is shown that usual spectrum of the synchrotron radiation is essentially affected by the presence of the solenoid (the Aharonov-Bohm effect). We believe that this deformation may be observed by spectroscopic methods of measurement. It is shown that
Aharonov-Bohm ring with fluctuating flux
NASA Astrophysics Data System (ADS)
Marquardt, Florian; Bruder, C.
2002-03-01
We consider a noninteracting system of electrons on a clean one-channel Aharonov-Bohm ring that is threaded by a fluctuating magnetic flux. The flux derives from a Caldeira-Leggett bath of harmonic oscillators. We address the influence of the bath on the following properties: one- and two-particle Green's functions, dephasing, persistent current, and visibility of the Aharonov-Bohm effect in cotunneling transport through the ring. For the bath spectra considered here (including Nyquist noise of an external coil), we find no dephasing in the linear transport regime at zero temperature.
Aharonov-Bohm Effect and Hidden Photons
Arias, Paola
2013-01-01
Signs of hypothetical light gauge bosons from a hidden sector may appear in Aharonov-Bohm-like experiments. The absence of signal in carried on experiments allow us to set a modest constraint to the mass and coupling constant of these particles. Our findings open the possibility to exploit the leaking of hidden magnetic field in a different setup of experiments.
Aharonov-Bohm Effect and Hidden Photons
Paola Arias
2013-09-17
Signs of hypothetical light gauge bosons from a hidden sector may appear in Aharonov-Bohm-like experiments. The absence of signal in carried on experiments allow us to set a modest constraint to the mass and coupling constant of these particles. Our findings open the possibility to exploit the leaking of hidden magnetic field in a different setup of experiments.
Aharonov-Bohm oscillation Magnetic field
Wang, Wei Hua
;+ + + + + + + + + + + EF AlGaAs GaAs Wave-function of 2DEG 2DEG undoped AlGaAs GaAs GaAs wafer doped 2DEG GaAs AlGaAs/GaAs Buffer GaAs/AlGaAs #12;2DEG metal gate Sample surface #12; AB #12; p k p=hk =(2/h)(1 pdl-2 pdl- 100083 20061219 #12; Aharonov-Bohm oscillation Magnetic field current Shot noise
Aharonov-Bohm effects of the photon
M. P. Silverman
1991-01-01
Although completely neutral systems are not expected to manifest the Aharonov-Bohm effect, it is shown that photons propagating through the vector potential field of a string of magnetic flux can, in principle, give rise to flux-dependent phenomena by means of nonlinear quantum electrodynamic processes involving virtual electtron-positron pairs. The magnetic flux dependence is determined for lowest order contributions to (i)
Aharonov-Bohm effects of the photon
NASA Astrophysics Data System (ADS)
Silverman, M. P.
1991-06-01
Although completely neutral systems are not expected to manifest the Aharonov-Bohm effect, it is shown that photons propagating through the vector potential field of a string of magnetic flux can, in principle, give rise to flux-dependent phenomena by means of nonlinear quantum electrodynamic processes involving virtual electtron-positron pairs. The magnetic flux dependence is determined for lowest order contributions to (i) vacuum polarisation, (ii) light scattering by an external scalar potential, and (iii) light-light scattering.
The electric Aharonov-Bohm effect
Weder, Ricardo [Departamento de Metodos Matematicos y Numericos, Instituto de Investigaciones en Matematicas Aplicadas y en Sistemas, Universidad Nacional Autonoma de Mexico, Apartado Postal 20-726, Mexico DF 01000 (Mexico)
2011-05-15
The seminal paper of Aharonov and Bohm [Phys. Rev. 115, 485 (1959)] is at the origin of a very extensive literature in some of the more fundamental issues in physics. They claimed that electromagnetic fields can act at a distance on charged particles even if they are identically zero in the region of space where the particles propagate, that the fundamental electromagnetic quantities in quantum physics are not only the electromagnetic fields but also the circulations of the electromagnetic potentials; what gives them a real physical significance. They proposed two experiments to verify their theoretical conclusions. The magnetic Aharonov-Bohm effect, where an electron is influenced by a magnetic field that is zero in the region of space accessible to the electron, and the electric Aharonov-Bohm effect where an electron is affected by a time-dependent electric potential that is constant in the region where the electron is propagating, i.e., such that the electric field vanishes along its trajectory. The Aharonov-Bohm effects imply such a strong departure from the physical intuition coming from classical physics that it is no wonder that they remain a highly controversial issue after more than fifty years, in spite of the fact that they are discussed in most of the text books in quantum mechanics. The magnetic case has been studied extensively. The experimental issues were settled by the remarkable experiments of Tonomura et al. [Phys. Rev. Lett. 48, 1443 (1982); Phys. Rev. Lett. 56, 792 (1986)] with toroidal magnets, that gave a strong evidence of the existence of the effect, and by the recent experiment of Caprez et al. [Phys. Rev. Lett. 99, 210401 (2007)] that shows that the results of the Tonomura et al. experiments cannot be explained by the action of a force. The theoretical issues were settled by Ballesteros and Weder [Commun. Math. Phys. 285, 345 (2009); J. Math. Phys. 50, 122108 (2009); Commun. Math. Phys. 303, 175 (2011)] who rigorously proved that quantum mechanics predicts the experimental results of Tonomura et al. and of Caprez et al. The electric Aharonov-Bohm effect has been much less studied. Actually, its existence, that has not been confirmed experimentally, is a very controversial issue. In their 1959 paper Aharonov and Bohm proposed an ansatz for the solution to the Schroedinger equation in regions where there is a time-dependent electric potential that is constant in space. It consists in multiplying the free evolution by a phase given by the integral in time of the potential. The validity of this ansatz predicts interference fringes between parts of a coherent electron beam that are subjected to different potentials. In this paper we prove that the exact solution to the Schroedinger equation is given by the Aharonov-Bohm ansatz up to an error bound in norm that is uniform in time and that decays as a constant divided by the velocity. Our results give, for the first time, a rigorous proof that quantum mechanics predicts the existence of the electric Aharonov-Bohm effect, under conditions that we provide. We hope that our results will stimulate the experimental research on the electric Aharonov-Bohm effect.
Photonic Aharonov-Bohm Effect Based on Dynamic Modulation
NASA Astrophysics Data System (ADS)
Fang, Kejie; Yu, Zongfu; Fan, Shanhui
2012-04-01
We show that when the refractive index of a photonic system is harmonically modulated, the phase of the modulation introduces an effective gauge potential for photons. This effective gauge potential can be used to create a photonic Aharonov-Bohm effect. We show that the photonic Aharonov-Bohm effect provides the optimal mechanism for achieving complete on-chip nonmagnetic optical isolation.
Photonic Aharonov–Bohm effect in photon–phonon interactions
Li, Enbang; Eggleton, Benjamin J.; Fang, Kejie; Fan, Shanhui
2014-01-01
The Aharonov–Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov–Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov–Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon–phonon interactions to demonstrate that photonic Aharonov–Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon–phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov–Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential. PMID:24476790
Photonic Aharonov-Bohm effect in photon-phonon interactions
NASA Astrophysics Data System (ADS)
Li, Enbang; Eggleton, Benjamin J.; Fang, Kejie; Fan, Shanhui
2014-01-01
The Aharonov-Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov-Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov-Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon-phonon interactions to demonstrate that photonic Aharonov-Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon-phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov-Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential.
Photonic Aharonov-Bohm effect in photon-phonon interactions.
Li, Enbang; Eggleton, Benjamin J; Fang, Kejie; Fan, Shanhui
2014-01-01
The Aharonov-Bohm effect is one of the most intriguing phenomena in both classical and quantum physics, and associates with a number of important and fundamental issues in quantum mechanics. The Aharonov-Bohm effects of charged particles have been experimentally demonstrated and found applications in various fields. Recently, attention has also focused on the Aharonov-Bohm effect for neutral particles, such as photons. Here we propose to utilize the photon-phonon interactions to demonstrate that photonic Aharonov-Bohm effects do exist for photons. By introducing nonreciprocal phases for photons, we observe experimentally a gauge potential for photons in the visible range based on the photon-phonon interactions in acousto-optic crystals, and demonstrate the photonic Aharonov-Bohm effect. The results presented here point to new possibilities to control and manipulate photons by designing an effective gauge potential. PMID:24476790
Geometry of the Aharonov Bohm Effect
NASA Astrophysics Data System (ADS)
Huerfano, R. S.; López, M. A.; Socolovsky, M.
2007-11-01
We show that the connection responsible for any Abelian or non-Abelian Aharonov Bohm effect with n parallel “magnetic” flux lines in ?3, lies in a trivial G-principal bundle P? M, i.e. P is isomorphic to the product M× G, where G is any path connected topological group; in particular a connected Lie group. We also show that two other bundles are involved: the universal covering space tilde{M}to M , where path integrals are computed, and the associated bundle P× G ? m ? M, where the wave function and its covariant derivative are sections.
Locality of the Aharonov-Bohm-Casher effect
NASA Astrophysics Data System (ADS)
Kang, Kicheon
2015-05-01
We address the question of locality versus nonlocality in the Aharonov-Bohm and the Aharonov-Casher effects. For this purpose, we investigate all possible configurations of ideal shielding of the overlap between the electromagnetic fields generated by a charge and by a magnetic flux and analyze their consequences on the Aharonov-Bohm-Casher interference. In a classical treatment of shielding, the Aharonov-Bohm-Casher effect vanishes regardless of the geometry of shielding when the local overlap of electromagnetic fields is completely eliminated. On the other hand, the result depends on the configuration of shielding if the charge quantization in the superconducting shield is taken into account. It is shown that our results are fully understood in terms of the fluctuating local-field interaction. Our analysis strongly supports the alternative view on the Aharonov-Bohm-Casher interference that the effects originate from the local action of electromagnetic fields.
Classical Electrodynamics without Fields and the Aharonov-Bohm effect
Eugene V. Stefanovich
2008-03-19
The Darwin-Breit Hamiltonian is applied to the Aharonov-Bohm experiment. In agreement with the standard Maxwell-Lorentz theory, the force acting on electrons from infinite solenoids or ferromagnetic rods vanishes. However, the interaction energies and phase factors of the electron wave packets are non-zero. This allows us to explain the Aharonov-Bohm effect without involvement of electromagnetic potentials, fields, and topological properties of space.
Relativistic Corrections to the Aharonov-Bohm Scattering
M. Gomes; J. M. C. Malbouisson; A. J. da Silva
1996-11-05
We determine the |p|/m expansion of the two body scattering amplitude of the quantum theory of a Chern-Simons field minimally coupled to a scalar field with quartic self-interaction. It is shown that the existence of a critical value of the self-interaction parameter for which the 2-particle amplitude reduces to the Aharonov-Bohm one is restricted to the leading, nonrelativistic, order. The subdominant terms correspond to relativistic corrections to the Aharonov-Bohm scattering.
Classical Electrodynamics without Fields and the Aharonov-Bohm effect
Eugene V. Stefanovich
2008-01-01
The Darwin-Breit Hamiltonian is applied to the Aharonov-Bohm experiment. In agreement with the standard Maxwell-Lorentz theory, the force acting on electrons from infinite solenoids or ferromagnetic rods vanishes. However, the interaction energies and phase factors of the electron wave packets are non-zero. This allows us to explain the Aharonov-Bohm effect without involvement of electromagnetic potentials, fields, and topological properties of
Photonic Aharonov-Bohm effect based on dynamic modulation.
Fang, Kejie; Yu, Zongfu; Fan, Shanhui
2012-04-13
We show that when the refractive index of a photonic system is harmonically modulated, the phase of the modulation introduces an effective gauge potential for photons. This effective gauge potential can be used to create a photonic Aharonov-Bohm effect. We show that the photonic Aharonov-Bohm effect provides the optimal mechanism for achieving complete on-chip nonmagnetic optical isolation. PMID:22587255
Aharonov-Bohm effect in optical activity
NASA Astrophysics Data System (ADS)
Tan, C. Z.
2010-09-01
Optically active media have the helical and dissymmetric crystal structure, which constrains the motions of the electrons to a helical path under the influence of the incident electric field. The charge flow along the helices induces a magnetic field in the direction of the axis of helices. The helical structure hence acts as natural micro-solenoids for the electromagnetic waves passing through them. Optical rotation is related to the difference in the accumulative Aharonov-Bohm (AB) phase between the right- and the left-circularly polarized waves. The AB phase is proportional to the angular momentum of an electron moving around the micro-solenoid. Originally the AB phase is shown to be a continuous function of the magnetic flux. However, quantization of the geometrical angular momentum leads to the quantized AB phase. The rotatory power and the Verdet constant are proportional to the refractive index of the medium. The quantized current in the micro-solenoid is proportional to the Bohr magneton and inversely proportional to the area of the helices.
Fan, Shanhui
Photonic Aharonov-Bohm Effect Based on Dynamic Modulation Kejie Fang Department of Physics potential can be used to create a photonic Aharonov-Bohm effect. We show that the photonic Aharonov-Bohm of the modulation can be used to create an effective gauge potential and, hence, a photonic Aharonov-Bohm effect
Holonomy, Aharonov-Bohm effect and phonon scattering in superfluids
Claudio Furtado; A. M. de M. Carvalho; L. C. Garcia de Andrade; F. Moraes
2004-01-08
In this article we discuss the analogy between superfluids and a spinning thick cosmic string. We use the geometrical approach to obtain the geometrical phases for a phonon in the presence of a vortex. We use loop variables for a geometric description of Aharonov-Bohm effect in these systems. We use holonomy transformations to characterize globally the "space-time" of a vortex and in this point of view we study the gravitational analog of the Aharonov-Bohm effect in this system. We demonstrate that in the general case the Aharonov-Bohm effect has a contribution both from the rotational and the translational holonomy. We study also Berrys quantum phase for phonons in this systems.
Anomalous aharonov-bohm gap oscillations in carbon nanotubes.
Sangalli, Davide; Marini, Andrea
2011-10-12
The gap oscillations caused by a magnetic flux penetrating a carbon nanotube represent one of the most spectacular observations of the Aharonov-Bohm effect at the nanoscale. Our understanding of this effect is, however, based on the assumption that the electrons are strictly confined on the tube surface, on trajectories that are not modified by curvature effects. Using an ab initio approach based on density functional theory, we show that this assumption fails at the nanoscale inducing important corrections to the physics of the Aharonov-Bohm effect. Curvature effects and electronic density that is spilled out of the nanotube surface are shown to break the periodicity of the gap oscillations. We predict the key phenomenological features of this anomalous Aharonov-Bohm effect in semiconductive and metallic tubes and the existence of a large metallic phase in the low flux regime of multiwalled nanotubes, also suggesting possible experiments to validate our results. PMID:21805987
The gravitational Aharonov-Bohm effect with photons
Edward G. Harris
1996-01-01
The analogy between general relativity and electromagnetism suggests that there is a gravitational analog of the Aharonov-Bohm effect. There is indeed such an effect. Since gravitation couples to all fields, the effect should exist for photons. There is a close connection with the Sagnac effect. Both the electromagnetic field and the gravitational field are classical fields, so the effect could
Analogue of Aharonov-Bohm effect in spin gauge theory
P C Naik
1986-01-01
We predict the possibility of observing analogue of the Aharonov-Bohm effect due to long range interaction between spins originating\\u000a in the framework of spin gauge theory developed earlier. The effect is predicted for both electrons (fermions) and photons.\\u000a Appropriate experimental set-ups are suggested.
QED processes beyond the Aharonov-Bohm effect
J. Audretsch; V. D. Skarzhinsky
1997-01-01
We consider QED - processes in the presence of an infinitely thin and infinitely long straight string with a magnetic flux inside it. The bremsstrahlung from an electron passing by the magnetic string and the electron-positron pair production by a single photon are reviewed. Based on the exact electron and positron solutions of the Dirac equation in the external Aharonov-Bohm
Exact quantum description of the Aharonov–Bohm effect
M. Y Choi; Minchul Lee
2004-01-01
The Aharonov–Bohm effect is considered in the fully quantum mechanical description, where the magnet as well as the moving charged particle is treated as a quantum object and interactions between them are mediated by virtual photon exchange. Employing the path integral representation, we not only establish the standard AB effect in an exact fashion but also reveal the origin of
Aharonov-Bohm effect without closing a loop
A. Retzker; S. Nussinov; B. Reznik; Y. Aharonov; A. Botero
2006-01-01
We discuss the consequences of the Aharonov-Bohm (AB) effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bipartite or multipartite entangled photons states, or alternatively, gives rise to an overall
Quantum Processes beyond the Aharonov-Bohm Effect
Jürgen Audretsch; Vladimir D. Skarzhinsky
1998-01-01
We consider QED processes in the presence of an infinitely thin and infinitely long straight string with a magnetic flux inside it. The bremsstrahlung from an electron passing by the magnetic string and the electron-positron pair production by a single photon are reviewed. Based on the exact electron and positron solutions of the Dirac equation in the external Aharonov-Bohm potential
Aharonov-Bohm effect and the mass of the photon
David G. Boulware; S. Deser
1989-01-01
We show that the Aharonov-Bohm effect requires that the vector potential couple minimally to matter, not that it be a gauge field: The effect is present in massive (finite-range) electrodynamics, reducing smoothly to the original result in the limit of infinite range. Indeed, it may be used to provide an experimental bound on the range which is much larger than
Symmetry-protected many-body Aharonov-Bohm effect
Santos, Luiz H.
It is known as a purely quantum effect that a magnetic flux affects the real physics of a particle, such as the energy spectrum, even if the flux does not interfere with the particle's path—the Aharonov-Bohm effect. Here ...
Group-theoretical derivation of Aharonov-Bohm phase shifts
Hagen, C. R. [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627-0171 (United States)] [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627-0171 (United States)
2013-02-15
The phase shifts of the Aharonov-Bohm effect are generally determined by means of the partial wave decomposition of the underlying Schroedinger equation. It is shown here that they readily emerge from an o(2,1) calculation of the energy levels employing an added harmonic oscillator potential which discretizes the spectrum.
Aharonov-Bohm Effect in Cyclotron and Synchrotron Radiations
Bagrov, V G; Levin, A; Tlyachev, V B
2000-01-01
We study the impact of Aharonov-Bohm solenoid on the radiation of a charged particle moving in a constant uniform magnetic field. With this aim in view, exact solutions of Klein-Gordon and Dirac equations are found in the magnetic-solenoid field. Using such solutions, we calculate exactly all the characteristics of one-photon spontaneous radiation both for spinless and spinning particle. Considering non-relativistic and relativistic approximations, we analyze cyclotron and synchrotron radiations in detail. Radiation peculiarities caused by the presence of the solenoid may be considered as a manifestation of Aharonov-Bohm effect in the radiation. In particular, it is shown that new spectral lines appear in the radiation spectrum. Due to angular distribution peculiarities of the radiation intensity, these lines can in principle be isolated from basic cyclotron and synchrotron radiation spectra
Aharonov-Bohm effect in cyclotron and synchrotron radiations
NASA Astrophysics Data System (ADS)
Bagrov, V. G.; Gitman, D. M.; Levin, A.; Tlyachev, V. B.
2001-07-01
We study the impact of Aharonov-Bohm solenoid on the radiation of a charged particle moving in a constant uniform magnetic field. With this aim in view, exact solutions of Klein-Gordon and Dirac equations are found in the magnetic-solenoid field. Using such solutions, we calculate exactly all the characteristics of one-photon spontaneous radiation both for spinless and spinning particle. Considering non-relativistic and relativistic approximations, we analyze cyclotron and synchrotron radiations in detail. Radiation peculiarities caused by the presence of the solenoid may be considered as a manifestation of Aharonov-Bohm effect in the radiation. In particular, it is shown that new spectral lines appear in the radiation spectrum. Due to angular distribution peculiarities of the radiation intensity, these lines can in principle be isolated from basic cyclotron and synchrotron radiation spectra.
Aharonov-Bohm Effect in Cyclotron and Synchrotron Radiations
V. G. Bagrov; D. M. Gitman; A. Levin; V. B. Tlyachev
2000-11-06
We study the impact of Aharonov-Bohm solenoid on the radiation of a charged particle moving in a constant uniform magnetic field. With this aim in view, exact solutions of Klein-Gordon and Dirac equations are found in the magnetic-solenoid field. Using such solutions, we calculate exactly all the characteristics of one-photon spontaneous radiation both for spinless and spinning particle. Considering non-relativistic and relativistic approximations, we analyze cyclotron and synchrotron radiations in detail. Radiation peculiarities caused by the presence of the solenoid may be considered as a manifestation of Aharonov-Bohm effect in the radiation. In particular, it is shown that new spectral lines appear in the radiation spectrum. Due to angular distribution peculiarities of the radiation intensity, these lines can in principle be isolated from basic cyclotron and synchrotron radiation spectra
Classical Electromagnetism and the Aharonov–Bohm Phase Shift
Timothy H. Boyer
2000-01-01
Although there is good experimental evidence for the Aharonov–Bohm phase shift occurring when a solenoid is placed between the beams forming a double-slit electron interference pattern, there has been very little analysis of the relevant classical electromagnetic forces. These forces between a point charge and a solenoid involve subtle relativistic effects of order v\\u000a2\\u000a\\/c\\u000a2\\u000a analogous to those
On the Nonabelian Aharonov Bohm Scattering of Spinless Particles
M. Gomes; L. C. Malacarne; A. J. da Silva
1998-12-01
The Aharonov Bohm scattering for spinless, isospin 1/2, particles interacting through a nonabelian Chern-Simons field is studied. Starting from the relativistic quantum field theory and using a Coulomb gauge formulation, the one loop renormalization program is implemented. Through the introduction of an intermediary cutoff, separating the regions of high and low integration momentum, the nonrelativistic limit is derived. The next to leading relativistic approximation is also determined. In this approach quantum field theory vacuum polarization effects are automatically incorporated.
Mathematical Justification of the Aharonov-Bohm Hamiltonian
César R. de Oliveira; Marciano Pereira
2008-01-01
It is presented, in the framework of nonrelativistic quantum mechanics, a justification of the usual Aharonov-Bohm hamiltonian\\u000a (with solenoid of radius greater than zero). This is obtained by way of increasing sequences of finitely long solenoids together\\u000a with a natural impermeability procedure; further, both limits commute. Such rigorous limits are in the strong resolvent sense\\u000a and in both ?2 and
Radiative corrections to the Aharonov-Bohm scattering
NASA Astrophysics Data System (ADS)
de Albuquerque, L. C.; Gomes, M.; da Silva, A. J.
2000-01-01
We consider the scattering of relativistic electrons from a thin magnetic flux tube and perturbatively calculate the order ? radiative correction to the first order Born approximation. We show also that the second order Born amplitude vanishes, and obtain a finite inclusive cross section for the one-body scattering which incorporates soft photon bremsstrahlung effects. Moreover, we determine the radiatively corrected Aharonov-Bohm potential and, in particular, verify that an induced magnetic field is generated outside of the flux tube.
Aharonov-Bohm effect for light in a moving medium
NASA Astrophysics Data System (ADS)
Vieira, Marcelo; Carvalho, Alexandre M. de M.; Furtado, Claudio
2014-07-01
In this paper we propose a way to detect the Aharonov-Bohm effect for light in a moving medium. We use the position-dependent photon wave function to describe the propagation of the photon in order to evaluate the phase shift acquired by the photon while it passes around a rotating cylinder embedded in a viscous fluid. We show that this phase depends on the speed of the fluid as well as the electromagnetic properties of the cylinder.
Aharonov-Bohm effect in cyclotron and synchrotron radiations
V. G. Bagrov; D. M. Gitman; A. Levin; V. B. Tlyachev
2001-01-01
We study the impact of Aharonov-Bohm solenoid on the radiation of a charged particle moving in a constant uniform magnetic field. With this aim in view, exact solutions of Klein-Gordon and Dirac equations are found in the magnetic-solenoid field. Using such solutions, we calculate exactly all the characteristics of one-photon spontaneous radiation both for spinless and spinning particle. Considering non-relativistic
Microscopic theory of the Aharonov-Bohm effect
E. Santos; I. Gonzalo
1999-01-01
A fully quantum theory of the Aharonov-Bohm effect is presented. It is based on the interaction, mediated by virtual photon exchange, between the traveling electron and the atomic magnetic dipoles of an infinitely long permanent magnet. The calculation involves second-order time-dependent perturbation theory. As expected, the relative phase between the two states---corresponding to the two alternative paths---interfering on the screen
Radiative Corrections to the Aharonov-Bohm Scattering
D'Albuquerque, L C; Da Silva, A J
2000-01-01
We consider the scattering of relativistic electrons from a thin magnetic flux tube and perturbatively calculate the order $\\alpha$, radiative correction, to the first order Born approximation. We show also that the second order Born amplitude vanishes, and obtain a finite inclusive cross section for the one-body scattering which incorporates soft photon bremsstrahlung effects. Moreover, we determine the radiatively corrected Aharonov-Bohm potential and, in particular, verify that an induced magnetic field is generated outside of the flux tube.
Aharonov–Bohm effect in cyclotron and synchrotron radiations
V. G. Bagrov; D. M. Gitman; A. Levin; V. B. Tlyachev
2001-01-01
We study the impact of Aharonov–Bohm solenoid on the radiation of a charged particle moving in a constant uniform magnetic field. With this aim in view, exact solutions of Klein–Gordon and Dirac equations are found in the magnetic-solenoid field. Using such solutions, we calculate exactly all the characteristics of one-photon spontaneous radiation both for spinless and spinning particle. Considering non-relativistic
Aharonov-Bohm effect and the mass of the photon
NASA Astrophysics Data System (ADS)
Boulware, David G.; Deser, S.
1989-11-01
We show that the Aharonov-Bohm effect requires that the vector potential couple minimally to matter, not that it be a gauge field: The effect is present in massive (finite-range) electrodynamics, reducing smoothly to the original result in the limit of infinite range. Indeed, it may be used to provide an experimental bound on the range which is much larger than the ``table-top'' apparatus, namely a lower limit of order 102 km.
Radiative Corrections to the Aharonov-Bohm Scattering
L. C. de Albuquerque; M. Gomes; A. J. da Silva
1999-06-22
We consider the scattering of relativistic electrons from a thin magnetic flux tube and perturbatively calculate the order $\\alpha$, radiative correction, to the first order Born approximation. We show also that the second order Born amplitude vanishes, and obtain a finite inclusive cross section for the one-body scattering which incorporates soft photon bremsstrahlung effects. Moreover, we determine the radiatively corrected Aharonov-Bohm potential and, in particular, verify that an induced magnetic field is generated outside of the flux tube.
Aharonov-Bohm oscillations in disordered topological insulator nanowires
J. H. Bardarson; P. W. Brouwer; J. E. Moore
2010-01-01
A direct signature of electron transport at the metallic surface of a\\u000atopological insulator is the Aharonov-Bohm oscillation observed in a recent\\u000astudy of Bi_2Se_3 nanowires [Peng et al., Nature Mater. 9, 225 (2010)] where\\u000aconductance was found to oscillate as a function of magnetic flux $\\\\phi$\\u000athrough the wire, with a period of one flux quantum $\\\\phi_0=h\\/e$ and maximum
Goddard III, William A.
. Recently, attention has also focused on the AharonovBohm effect for neutral particles, such as photons-optic crystals, and demonstrate the photonic AharonovBohm effect. The results presented here point to newARTICLE Received 5 Nov 2013 | Accepted 9 Jan 2014 | Published 30 Jan 2014 Photonic AharonovBohm
Experimental demonstration of a photonic Aharonov-Bohm effect at radio frequencies
NASA Astrophysics Data System (ADS)
Fang, Kejie; Yu, Zongfu; Fan, Shanhui
2013-02-01
Building upon recent theoretical proposals for creating an effective gauge field for photons, we experimentally demonstrate the photonic Aharonov-Bohm effect. The effect relies on the nonreciprocal phase acquired by photons during photonic transitions. Our photonic Aharonov-Bohm interferometer is broadly tunable with a contrast ratio above 30 dB, as the operating frequency varies between 8 and 12 MHz.
Parity violation in Aharonov-Bohm systems: The spontaneous Hall effect
R. Emparan; M. A. Valle Basagoiti
1994-01-01
We show how macroscopic manifestations of P (and T) symmetry breaking can arise in a simple system subject to Aharonov-Bohm interactions. Specifically, we study the conductivity of a gas of charged particles moving through a dilute array of flux tubes. The interaction of the electrons with the flux tubes is taken to be of a purely Aharonov-Bohm type. We find
Inelastic transport through Aharonov-Bohm interferometer in Kondo regime
Yoshii, Ryosuke; Eto, Mikio [Faculty of Science and Technology, Keio University, Yokohama 223-8522 (Japan); Sakano, Rui [Institute for Solid State Physics, University of Tokyo, Kashiwa 277-8581 (Japan); Affleck, Ian [Department of Physics and Astronomy, University of British Columbia, Vancouver (Canada)
2013-12-04
We formulate elastic and inelastic parts of linear conductance through an Aharonov-Bohm (AB) ring with an embedded quantum dot in the Kondo regime. The inelastic part G{sub inel} is proportional to T{sup 2} when the temperature T is much smaller than the Kondo temperature T{sub K}, whereas it is negligibly small compared with elastic part G{sub el} when T ? T{sub K}. G{sub inel} weakly depends on the magnetic flux penetrating the AB ring, which disturbs the precise detection of G{sub el}/(G{sub el}+G{sub inel}) by the visibility of AB oscillation.
QED processes beyond the Aharonov-Bohm effect
Audretsch, J
1998-01-01
We consider QED - processes in the presence of an infinitely thin and infinitely long straight string with a magnetic flux inside it. The bremsstrahlung from an electron passing by the magnetic string and the electron-positron pair production by a single photon are reviewed. Based on the exact electron and positron solutions of the Dirac equation in the external Aharonov-Bohm potential we present matrix elements for these processes. The dependence of the resulting cross sections on energies, directions and polarizations of the involved particles is discussed for low energies.
QED processes beyond the Aharonov-Bohm effect
J. Audretsch; V. D. Skarzhinsky
1997-09-14
We consider QED - processes in the presence of an infinitely thin and infinitely long straight string with a magnetic flux inside it. The bremsstrahlung from an electron passing by the magnetic string and the electron-positron pair production by a single photon are reviewed. Based on the exact electron and positron solutions of the Dirac equation in the external Aharonov-Bohm potential we present matrix elements for these processes. The dependence of the resulting cross sections on energies, directions and polarizations of the involved particles is discussed for low energies.
The gravitational Aharonov-Bohm effect with photons
NASA Astrophysics Data System (ADS)
Harris, Edward G.
1996-04-01
The analogy between general relativity and electromagnetism suggests that there is a gravitational analog of the Aharonov-Bohm effect. There is indeed such an effect. Since gravitation couples to all fields, the effect should exist for photons. There is a close connection with the Sagnac effect. Both the electromagnetic field and the gravitational field are classical fields, so the effect could have been predicted in the interval between the publication of the theory of general relativity in 1915 and the discovery of quantum mechanics in the mid 1920s.
Aharonov-Bohm effect without closing a loop
NASA Astrophysics Data System (ADS)
Retzker, A.; Aharonov, Y.; Botero, A.; Nussinov, S.; Reznik, B.
2006-03-01
We discuss the consequences of the Aharonov-Bohm (AB) effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bipartite or multipartite entangled photons states, or alternatively, gives rise to an overall AB phase that can be measured relative to another reference system. These setups involve processes of annihilation or creation of electron-hole pairs. We discuss the relevance of such effects in “vacuum birefringence" in QED, and comment on their connection to other known effects.
Optically induced Aharonov-Bohm effect in mesoscopic rings
NASA Astrophysics Data System (ADS)
Sigurdsson, H.; Kibis, O. V.; Shelykh, I. A.
2014-12-01
We show theoretically that strong electron coupling to circularly polarized photons in non-singly-connected nanostructures results in the appearance of an artificial gauge field that changes the electron phase. The effect arises from the breaking of time-reversal symmetry and is analogous to the well-known Aharonov-Bohm phase effect. It can manifest itself in the oscillations of conductance as a function of the intensity and frequency of the illumination. The theory of the effect is elaborated for mesoscopic rings in both ballistic and diffusive regimes.
Realization of adiabatic Aharonov-Bohm scattering with neutrons
Erik Sjöqvist; Martin Almquist; Ken Mattsson; Zeynep Nilhan Gürkan; Björn Hessmo
2015-03-08
The adiabatic Aharonov-Bohm (AB) effect is a manifestation of the Berry phase acquired when some slow variables take a planar spin around a loop. While the effect has been observed in molecular spectroscopy, direct measurement of the topological phase shift in a scattering experiment has been elusive in the past. Here, we demonstrate an adiabatic AB effect for neutrons that scatter on a long straight current-carrying wire. We propose an experiment to verify the effect and demonstrate its feasibility by explicit simulation of the dynamics of unpolarized very slow neutrons that scatter on the wire under realistic conditions.
NASA Astrophysics Data System (ADS)
Kawaguchi, Satoshi
2015-05-01
In this study, we consider the Kondo temperature and differential conductance for an Aharonov-Bohm ring with an embedded quantum dot connected with noncollinear ferromagnetic leads. Starting from the tight-binding model, we propose an equivalent Anderson model, in which the density of states depends on the Aharonov-Bohm phase. By applying the poor man's scaling approach to the Hamiltonian, we derive the dependences of the Kondo temperature and differential conductance on the Aharonov-Bohm phase, spin polarization, angle of magnetic moment, and asymmetry parameters. We show conditions for the nonmonotonic behavior of the differential conductance in terms of the spin splitting and Aharonov-Bohm phase. In addition, by extending the model to the case of a finite ring size, we show that the Kondo temperature crucially depends on ring size, but the properties of the scaled temperature are similar to ones for the small ring-size limit.
What did we learn from the Aharonov-Bohm effect? Is spin 1/2 different?
Peshkin, M.
1994-06-01
I review what has been learned about fundamental issues in quantum mechanics from the Aharonov-Bohm effect. Following that, I consider the Aharonov-Casher effect and the Scalar Aharonov-Bohm effect, in both of which a spin-1/2 particle interacts with a local electromagnetic field through its magnetic moment, and conclude that those effects can be described as observable effects of local torques.
Photon mass and quantum effects of the Aharonov-Bohm type
NASA Astrophysics Data System (ADS)
Spavieri, G.; Rodriguez, M.
2007-05-01
The magnetic field due to the photon rest mass mph modifies the standard results of the Aharonov-Bohm effect for electrons, and of other recent quantum effects. For the effect involving a coherent superposition of beams of particles with opposite electromagnetic properties, by means of a tabletop experiment, the limit mph?10-51g is achievable, improving by 6 orders of magnitude that derived by Boulware and Deser for the Aharonov-Bohm effect.
Photon mass and quantum effects of the Aharonov-Bohm type
Spavieri, G
2007-01-01
The magnetic field due to the photon rest mass $m_{ph}$ modifies the standard results of the Aharonov-Bohm effect for electrons, and of other recent quantum effects. For the effect involving a coherent superposition of beams of particles with opposite electromagnetic properties, by means of a table-top experiment, the limit $m_{ph}x10^{-51}g$ is achievable, improving by 6 orders of magnitude that derived by Boulware and Deser for the Aharonov-Bohm effect.
Photon mass and quantum effects of the Aharonov-Bohm type
G. Spavieri; M. Rodriguez
2007-05-08
The magnetic field due to the photon rest mass $m_{ph}$ modifies the standard results of the Aharonov-Bohm effect for electrons, and of other recent quantum effects. For the effect involving a coherent superposition of beams of particles with opposite electromagnetic properties, by means of a table-top experiment, the limit $m_{ph}x10^{-51}g$ is achievable, improving by 6 orders of magnitude that derived by Boulware and Deser for the Aharonov-Bohm effect.
Graphene rings in magnetic fields: Aharonov-Bohm effect and valley splitting
2010-01-01
We study the conductance of mesoscopic graphene rings in the presence of a perpendicular magnetic field by means of numerical calculations based on a tight-binding model. First, we consider the magnetoconductance of such rings and observe the Aharonov-Bohm effect. We investigate different regimes of the magnetic flux up to the quantum Hall regime, where the Aharonov-Bohm oscillations are suppressed. Results
Microscopic theory of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Santos, E.; Gonzalo, I.
1999-02-01
A fully quantum theory of the Aharonov-Bohm effect is presented. It is based on the interaction, mediated by virtual photon exchange, between the traveling electron and the atomic magnetic dipoles of an infinitely long permanent magnet. The calculation involves second-order time-dependent perturbation theory. As expected, the relative phase between the two states—corresponding to the two alternative paths—interfering on the screen agrees with that predicted in the usual theory. However our method may allow to get corrections, for instance due to the size and shape of the electron wave packet, the possible soft-photon emission or the excitation of the atoms in the magnet.
Classical light analogue of the nonlocal Aharonov-Bohm effect
Satapathy, Nandan; Mehta, Poonam; Sinha, Supurna; Samuel, Joseph; Ramachandran, Hema
2012-01-01
We demonstrate the existence of a non-local geometric phase in the intensity-intensity correlations of classical incoherent light, that is not seen in the lower order correlations. This two-photon Pancharatnam phase was observed and modulated in a Mach-Zehnder interferometer. Using acousto-optic interaction, independent phase noise was introduced to light in the two arms of the interferometer to create two independent incoherent classical sources from laser light. The experiment is the classical optical analogue of the multi-particle Aharonov-Bohm effect. As the trajectory of light over the Poincare sphere introduces a phase shift observable only in the intensity-intensity correlation, it provides a means of deflecting the two-photon wavefront, while having no effect on single photons.
Classical light analogue of the nonlocal Aharonov-Bohm effect
Nandan Satapathy; Deepak Pandey; Poonam Mehta; Supurna Sinha; Joseph Samuel; Hema Ramachandran
2012-02-13
We demonstrate the existence of a non-local geometric phase in the intensity-intensity correlations of classical incoherent light, that is not seen in the lower order correlations. This two-photon Pancharatnam phase was observed and modulated in a Mach-Zehnder interferometer. Using acousto-optic interaction, independent phase noise was introduced to light in the two arms of the interferometer to create two independent incoherent classical sources from laser light. The experiment is the classical optical analogue of the multi-particle Aharonov-Bohm effect. As the trajectory of light over the Poincare sphere introduces a phase shift observable only in the intensity-intensity correlation, it provides a means of deflecting the two-photon wavefront, while having no effect on single photons.
Size effects in Aharonov-Bohm graphene rings.
Yan, Cong-Hua; Wei, Lian-Fu
2010-07-28
Aharonov-Bohm (AB) effects in mesoscopic metal rings have been extensively studied. In this paper, we investigate these effects on the persistent currents (PCs) in a closed graphene ring with broken time-reversal symmetry. A hard boundary condition is introduced to describe the Dirac electrons moving along such a ring-shaped configuration, and then the induced persistent currents are numerically calculated. Differing from the properties of PCs revealed in the metal AB rings, we show that the present PCs neither show the regular saw-tooth-like features nor present the odd-even symmetry of the electron number. More interestingly, we show that the energy difference between the two valleys and the amplitude of the oscillating PCs increase with the decrease (increase) of the radius (width) of the graphene ring. Our results imply that the AB effect and size-dependent PCs in ring-shaped microstructures could be tested at room temperature. PMID:21399310
Size effects in Aharonov-Bohm graphene rings
NASA Astrophysics Data System (ADS)
Yan, Cong-Hua; Wei, Lian-Fu
2010-07-01
Aharonov-Bohm (AB) effects in mesoscopic metal rings have been extensively studied. In this paper, we investigate these effects on the persistent currents (PCs) in a closed graphene ring with broken time-reversal symmetry. A hard boundary condition is introduced to describe the Dirac electrons moving along such a ring-shaped configuration, and then the induced persistent currents are numerically calculated. Differing from the properties of PCs revealed in the metal AB rings, we show that the present PCs neither show the regular saw-tooth-like features nor present the odd-even symmetry of the electron number. More interestingly, we show that the energy difference between the two valleys and the amplitude of the oscillating PCs increase with the decrease (increase) of the radius (width) of the graphene ring. Our results imply that the AB effect and size-dependent PCs in ring-shaped microstructures could be tested at room temperature.
Aharonov-Bohm Hamiltonians, isospectrality and minimal partitions
NASA Astrophysics Data System (ADS)
Bonnaillie-Noël, V.; Helffer, B.; Hoffmann-Ostenhof, T.
2009-05-01
The spectral analysis of Aharonov-Bohm Hamiltonians with flux \\frac12 leads surprisingly to a new insight on some questions of isospectrality appearing for example in Jakobson et al (2006 J. Comput. Appl. Math. 194 141-55) and Levitin et al (J. Phys. A: Math. Gen. 39 2073-82) and of minimal partitions (Helffer et al 2009 Ann. Inst. H. Poincaré Anal. Non Linéaire 26 101-38). We will illustrate this point of view by discussing the question of spectral minimal 3-partitions for the rectangle \\big]{-}\\frac a2,\\frac a2\\big[\\times \\big]{-}\\frac b2,\\frac b2\\big[ , with 0 < a <= b. It has been observed in Helffer et al (2009 Ann. Inst. H. Poincaré Anal. Non Linéaire 26 101-38) that when 0<\\frac ab < \\sqrt{\\vphantom{A^A}\\smash{\\\\frac 38}} the minimal 3-partition is obtained by the three nodal domains of the third eigenfunction corresponding to the three rectangles \\big]{-}\\frac a2,\\frac a2\\big[\\times \\big] {-}\\frac b2,-\\frac b6\\big[, \\big]{-}\\frac a2,\\frac a2\\big[\\times \\big]{-}\\frac b6,\\frac b6\\big[ and \\big]{-}\\frac a2,\\frac a2\\big[\\times \\big] \\frac b6, \\frac b2\\big[ . We will describe a possible mechanism of transition for increasing \\frac ab between these nodal minimal 3-partitions and non-nodal minimal 3-partitions at the value \\sqrt{\\vphantom{A^A}\\smash{\\\\frac 38}} and discuss the existence of symmetric candidates for giving minimal 3-partitions when \\sqrt{\\vphantom{A^A}\\smash{\\\\frac 38}} <\\frac ab \\leq 1 . Numerical analysis leads very naturally to nice questions of isospectrality which are solved by the introduction of Aharonov-Bohm Hamiltonians or by going on the double covering of the punctured rectangle.
Marini, Andrea
;The AB effect in carbon nano-tubes (CNTs) A. Bachtold et al., Nature 397, 673 (1999) S. Zaric et alCarbon nanotubes in confined magneticCarbon nanotubes in confined magnetic fields: Aharonov;OutlineOutline Aharonov-Bohm oscillations in Carbon nanotubes Curvature effects Persistent currents #12
Aharonov--Bohm effect, electrodynamics postulates, and Lorentz condition
V. B. Bobrov; S. A. Trigger; G. J. F. van Heijst; P. P. J. M. Schram
2013-06-28
The problem of the relation between the Ahronov-Bohm effect and traditional postulates of electrodynamics, which claim that only electric and magnetic fields are observable, is resolved by denial of the statement about validity of the Maxwell equations for microscopic fields. We proceed from the idea that the Maxwell equations, as the generalization of experimental data, are valid only for averaged values. We show that microscopic electrodynamics should be based on postulation of the d'Alembert equations for four-vector of the electromagnetic field potential. The Lorentz condition is valid only for the averages and provides the implementation of the Maxwell equations for averages. This concept eliminates the problem of electromagnetic field quantization and provides the correctness of all known results of quantum electrodynamics. Therefore, the "virtuality" of the longitudinal and scalar photons has a formal mathematical character, conditioned by the Maxwell equations for averaged fields. The longitudinal and scalar photons provide not only the Coulomb interaction of charged particles, but also allow the electrical Aharonov-Bohm effect.
Optical Signatures of the Aharonov-Bohm Phase in Single-Walled Carbon Nanotubes
NASA Astrophysics Data System (ADS)
Zaric, Sasa; Ostojic, Gordana N.; Kono, Junichiro; Shaver, Jonah; Moore, Valerie C.; Strano, Michael S.; Hauge, Robert H.; Smalley, Richard E.; Wei, Xing
2004-05-01
We report interband magneto-optical spectra for single-walled carbon nanotubes in high magnetic fields up to 45 tesla, confirming theoretical predictions that the band structure of a single-walled carbon nanotube is dependent on the magnetic flux ? threading the tube. We have observed field-induced optical anisotropy as well as red shifts and splittings of absorption and photoluminescence peaks. The amounts of shifts and splittings depend on the value of ?/?0 and are quantitatively consistent with theories based on the Aharonov-Bohm effect. These results represent evidence of the influence of the Aharonov-Bohm phase on the band gap of a solid.
The Aharonov-Bohm effect: A quantum or a relativistic phenomenon?
K. Wilhelm; B. N. Dwivedi
2014-08-23
The Aharonov-Bohm effect is considered by most authors as a quantum effect, but a generally accepted explanation does not seem to be available. The phenomenon is studied here under the assumption that hypothetical electric dipole distributions configured by moving charges in the solenoid act on the electrons as test particles. The relative motions of the interacting charged particles introduce relativistic time dilations. The massless dipoles are postulated as part of an impact model that has recently been proposed to account for the far-reaching electrostatic forces between charged particles described by Coulomb's law. The model provides a quantitative explanation of the Aharonov-Bohm effect.
Stokes' theorem, gauge symmetry and the time-dependent Aharonov-Bohm effect
Macdougall, James, E-mail: jbm34@mail.fresnostate.edu; Singleton, Douglas, E-mail: dougs@csufresno.edu [Department of Physics, California State University Fresno, Fresno, California 93740-8031 (United States)] [Department of Physics, California State University Fresno, Fresno, California 93740-8031 (United States)
2014-04-15
Stokes' theorem is investigated in the context of the time-dependent Aharonov-Bohm effect—the two-slit quantum interference experiment with a time varying solenoid between the slits. The time varying solenoid produces an electric field which leads to an additional phase shift which is found to exactly cancel the time-dependent part of the usual magnetic Aharonov-Bohm phase shift. This electric field arises from a combination of a non-single valued scalar potential and/or a 3-vector potential. The gauge transformation which leads to the scalar and 3-vector potentials for the electric field is non-single valued. This feature is connected with the non-simply connected topology of the Aharonov-Bohm set-up. The non-single valued nature of the gauge transformation function has interesting consequences for the 4-dimensional Stokes' theorem for the time-dependent Aharonov-Bohm effect. An experimental test of these conclusions is proposed.
Modular Momentum of the Aharonov-Bohm Effect on Noncommutative Lattices
Takeo Miura
2012-07-23
Based on the technique of noncommutative geometry, it is shown that, by means of the concept of the theta quantization, there is an equivalence between the notion of the modular momentum of the Aharonov-Bohm effect and the notion of a noncommutative lattice over a circle poset.
Photon localisation, the Pryce operator and the Aharonov-Bohm effect
Arun Kumar Pati
1996-01-01
The existence of the Pryce operator allows us to localise a photon optimally, although not precisely, in space and time. We interpret the additional term in the Pryce operator as a non-Abelian gauge potential in the momentum space and predict an Aharonov-Bohm effect for the photon.
Time-dependent electron transport through an Aharonov–Bohm ring embedded with two quantum dots
Hui Pan; Li-Na Zhao; Rong Lü
2008-01-01
The time-dependent electron transport through an Aharonov–Bohm ring embedded with two quantum dots in the presence of external microwave (MW) fields are investigated theoretically by using the nonequilibrium Green's function method. Whether the MW field can induce or suppress the Fano resonance depends on the part to which the field is applied. When the MW field is applied only to
Electron-positron pair production in the Aharonov-Bohm potential
Vladimir D. Skarzhinsky; Jürgen Audretsch; Ulf Jasper
1996-01-01
In the framework of QED we evaluate the cross section for electron-positron pair production by a single photon in the presence of the external Aharonov-Bohm potential in first order of perturbation theory. We analyze energy, angular, and polarization distributions at different energy regines: near the threshold and at high photon energies.
Photon localisation, the Pryce operator and the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Pati, Arun Kumar
1996-02-01
The existence of the Pryce operator allows us to localise a photon optimally, although not precisely, in space and time. We interpret the additional term in the Pryce operator as a non-Abelian gauge potential in the momentum space and predict an Aharonov-Bohm effect for the photon.
Polarized excitons in nanorings and the optical Aharonov-Bohm effect
A. O. Govorov; S. E. Ulloa; K. Karrai; R. J. Warburton
2002-01-01
The quantum nature of matter lies in the wave function phases that accumulate while particles move along their trajectories. A prominent example is the Aharonov-Bohm phase, which has been studied in connection with the conductance of nanostructures. However, optical response in solids is determined by neutral excitations, for which no sensitivity to magnetic flux would be expected. We propose a
On the possibility of transmitting signals by means of the Aharonov-Bohm effect
A. N. Ageev; A. G. Chirkov; B. N. Shalaev; L. A. Markova
2010-01-01
A mental experiment on the possible effect of an alternating current flowing along generating lines of an infinitely long cylinder on the interference diffraction pattern of microparticles has been considered. The possibility of exciting and detecting electromagnetic waves, which correspond to a zero electromagnetic field, and transmitting signals by means of the Aharonov-Bohm effect changing the phase of the electron
The Aharonov-Bohm effect and its applications to electron phase microscopy
Tonomura, Akira
2006-01-01
The Aharonov-Bohm effect was conclusively established by a series of our electron interference experiments, with the help of some advanced techniques, such as coherent field-emission electron beams and microlithography. Using this fundamental principle behind the interaction of an electron wave with electromagnetic fields, new observation techniques were developed to directly observe microscopic objects and quantum phenomena previously unobservable. PMID:25792772
Aharonov-Bohm oscillations in the exciton luminescence from a semiconductor nanoring
Chemnitz, Technische Universität
Aharonov-Bohm oscillations in the exciton luminescence from a semiconductor nanoring R. A. Romer 1 of an exciton con#12;ned within a semiconductor ring is studied theoretically. We demonstrate that, despite of InGaAs self-assembled in the course of epitaxial growth in a GaAs matrix. Together with generic
Aharonov-Bohm-like scattering, localization, and novel electronic states in hydrogenated graphene
Andrey Shytov; Dmitry Abanin; Leonid Levitov
2009-01-01
Metallic nature of transport in graphene, which is fairly robust with respect to varying amounts of disorder, changes in an unexpected way when vacancies are introduced in this material. At low energies, near the Dirac point, electron scattering on vacancies mimics scattering on Aharonov-Bohm solenoids carrying unit flux. This type of scattering results in a very narrow band of states
The Aharonov-Bohm effect and Tonomura et al. experiments: Rigorous results
Ballesteros, Miguel; Weder, Ricardo [Projet POems, Domaine de Voluceau-Rocquencourt, Institut National de Recherche en Informatique et en Automatique Paris-Rocquencourt, BP 105, 78153 Le Chesnay Cedex France (France)
2009-12-15
The Aharonov-Bohm effect is a fundamental issue in physics. It describes the physically important electromagnetic quantities in quantum mechanics. Its experimental verification constitutes a test of the theory of quantum mechanics itself. The remarkable experiments of Tonomura et al. ['Observation of Aharonov-Bohm effect by electron holography', Phys. Rev. Lett 48, 1443 (1982) and 'Evidence for Aharonov-Bohm effect with magnetic field completely shielded from electron wave', Phys. Rev. Lett 56, 792 (1986)] are widely considered as the only experimental evidence of the physical existence of the Aharonov-Bohm effect. Here we give the first rigorous proof that the classical ansatz of Aharonov and Bohm of 1959 ['Significance of electromagnetic potentials in the quantum theory', Phys. Rev. 115, 485 (1959)], that was tested by Tonomura et al., is a good approximation to the exact solution to the Schroedinger equation. This also proves that the electron, that is, represented by the exact solution, is not accelerated, in agreement with the recent experiment of Caprez et al. in 2007 ['Macroscopic test of the Aharonov-Bohm effect', Phys. Rev. Lett. 99, 210401 (2007)], that shows that the results of the Tonomura et al. experiments can not be explained by the action of a force. Under the assumption that the incoming free electron is a Gaussian wave packet, we estimate the exact solution to the Schroedinger equation for all times. We provide a rigorous, quantitative error bound for the difference in norm between the exact solution and the Aharonov-Bohm Ansatz. Our bound is uniform in time. We also prove that on the Gaussian asymptotic state the scattering operator is given by a constant phase shift, up to a quantitative error bound that we provide. Our results show that for intermediate size electron wave packets, smaller than the ones used in the Tonomura et al. experiments, quantum mechanics predicts the results observed by Tonomura et al. with an error bound smaller than 10{sup -99}. It would be quite interesting to perform experiments with electron wave packets of intermediate size. Furthermore, we provide a physical interpretation of our error bound.
Noncommutative Correction to the Aharonov-Bohm Scattering: a Field Theory Approach
M. A. Anacleto; M. Gomes; A. J. da Silva; D. Spehler
2004-07-15
We study a noncommutative nonrelativistic theory in 2+1 dimensions of a scalar field coupled to the Chern-Simons field. In the commutative situation this model has been used to simulate the Aharonov-Bohm effect in the field theory context. We verified that, contrarily to the commutative result, the inclusion of a quartic self-interaction of the scalar field is not necessary to secure the ultraviolet renormalizability of the model. However, to obtain a smooth commutative limit the presence of a quartic gauge invariant self-interaction is required. For small noncommutativity we fix the corrections to the Aharonov-Bohm scattering and prove that up to one-loop the model is free from dangerous infrared/ultraviolet divergences.
Nonrelativistic Limit of the Scalar Chern-Simons Theory and the Aharonov-Bohm Scattering
M. Gomes; J. M. C. Malbouisson; A. J. da Silva
1998-01-28
We study the nonrelativistic limit of the quantum theory of a Chern-Simons field minimally coupled to a scalar field with quartic self-interaction. The renormalization of the relativistic model, in the Coulomb gauge, is discussed. We employ a procedure to calculate scattering amplitudes for low momenta that generates their $|p|/m$ expansion and separates the contributions coming from high and low energy intermediary states. The two body scattering amplitude is calculated up to order $p^2/m^2$. It is shown that the existence of a critical value of the self-interaction parameter for which the 2-particle scattering amplitude reduces to the Aharonov-Bohm one is a strictly nonrelativistic feature. The subdominant terms correspond to relativistic corrections to the Aharonov-Bohm scattering. A nonrelativistic reduction scheme and an effective nonrelativistic Lagrangian to account for the relativistic corrections are proposed.
Parity violation in Aharonov-Bohm systems: The spontaneous Hall effect
NASA Astrophysics Data System (ADS)
Emparan, R.; Valle Basagoiti, M. A.
1994-05-01
We show how macroscopic manifestations of P (and T) symmetry breaking can arise in a simple system subject to Aharonov-Bohm interactions. Specifically, we study the conductivity of a gas of charged particles moving through a dilute array of flux tubes. The interaction of the electrons with the flux tubes is taken to be of a purely Aharonov-Bohm type. We find that the system exhibits a nonzero transverse conductivity, i.e., a spontaneous Hall effect. This is in contrast to the fact that the cross sections for both scattering and bremsstrahlung (soft-photon emission) of a single electron from a flux tube are invariant under reflections. We argue that the asymmetry in the conductivity coefficients arises from many-body effects. On the other hand, the transverse conductivity has the same dependence on universal constants that appears in the quantum Hall effect, a result that we relate to the validity of the mean-field approximation.
Aharonov-Bohm effect in quantum-to-classical correspondence of the Heisenberg principle
NASA Astrophysics Data System (ADS)
Lin, De-Hone; Chang, Jee-Gong; Hwang, Chi-Chuan
2003-04-01
The exact energy spectrum and wave function of a charged particle moving in the Coulomb field and Aharonov-Bohm’s magnetic flux are solved by the nonintegrable phase factor. The universal formula for the matrix elements of the radial operator r? of arbitrary power ? is given by an analytical solution. The difference between the classical limit of matrix elements of inverse radius in quantum mechanics and the Fourier components of the corresponding quantity for the pure Coulomb system in classical mechanics is examined in reference to the correspondence principle of Heisenberg. Explicit calculation shows that the influence of nonlocal Aharonov-Bohm effect exists even in the classical limit. The semiclassical quantization rule for systems containing the topological effect is presented in the light of Heisenberg’s corresponding principle.
Parity Violation in Aharonov-Bohm Systems: The Spontaneous Hall Effect
R. Emparan; M. A. Valle Basagoiti
1993-12-21
We show how macroscopic manifestations of $P$ (and $T$) symmetry breaking can arise in a simple system subject to Aharonov-Bohm interactions. Specifically, we study the conductivity of a gas of charged particles moving through a dilute array of flux tubes. The interaction of the electrons with the flux tubes is taken to be of a purely Aharonov-Bohm type. We find that the system exhibits a non-zero transverse conductivity, i.e., a spontaneous Hall effect. This is in contrast with the fact that the cross sections for both scattering and bremsstrahlung (soft photon emission) of a single electron from a flux tube are invariant under reflections. We argue that the asymmetry in the conductivity coefficients arises from many-body effects. On the other hand, the transverse conductivity has the same dependence on universal constants that appears in the Quantum Hall Effect, a result that we relate to the validity of the Mean Field approximation.
Flux-dependent level attraction in double-dot Aharonov-Bohm interferometers
Björn Kubala; Jürgen König
2002-01-01
We study electron transport through a closed Aharonov-Bohm interferometer containing two noninteracting single-level quantum dots. The quantum-dot levels are coupled to each other indirectly via the leads. We find that this coupling yields signatures of an effective flux-dependent level attraction in the linear conductance. Furthermore, we predict a suppression of transport when both levels are close to the Fermi level
NASA Astrophysics Data System (ADS)
Kibis, O. V.; Sigurdsson, H.; Shelykh, I. A.
2015-06-01
We show theoretically that the strong coupling of circularly polarized photons to an exciton in ringlike semiconductor nanostructures results in physical nonequivalence of clockwise and counterclockwise exciton rotations in the ring. As a consequence, the stationary energy splitting of exciton states corresponding to these mutually opposite rotations appears. This excitonic Aharonov-Bohm effect depends on the intensity and frequency of the circularly polarized field and can be detected in state-of-the-art optical experiments.
Polarized excitons in nanorings and the optical Aharonov-Bohm effect
A. O. Govorov; K. Karrai; R. J. Warburton
2002-01-01
The quantum nature of matter lies in the wave function phases that accumulate\\u000awhile particles move along their trajectories. A prominent example is the\\u000aAharonov-Bohm phase, which has been studied in connection with the conductance\\u000aof nanostructures. However, optical response in solids is determined by neutral\\u000aexcitations, for which no sensitivity to magnetic flux would be expected. We\\u000apropose a
On the possibility of transmitting signals by means of the Aharonov-Bohm effect
A. N. Ageev; A. G. Chirkov; B. N. Shalaev; L. A. Markova
2010-01-01
A mental experiment on the possible effect of an alternating current flowing along generating lines of an infinitely long\\u000a cylinder on the interference diffraction pattern of microparticles has been considered. The possibility of exciting and detecting\\u000a electromagnetic waves, which correspond to a zero electromagnetic field, and transmitting signals by means of the Aharonov-Bohm\\u000a effect changing the phase of the electron
Mesoscopic Transport Through a Quantum-Dot-Embedded Aharonov-Bohm Ring Threaded with AC Flux
Hong-Kang Zhao
2001-01-01
The electron transporting through a mesoscopic ring embedded with one quantum dot and threaded by dc and ac magnetic fluxes is investigated by employing the Keldysh nonequilibrium Green function technique. The tunneling current and differential conductance are derived to show the Aharonov-Bohm-like effect induced by external magnetic fluxes. The multi-channel ring and multi-level quantum dot system is studied. The quenching
Photon mass and quantum effects of the Aharonov-Bohm type
G. Spavieri; M. Rodriguez
2007-01-01
The magnetic field due to the photon rest mass mph modifies the standard results of the Aharonov-Bohm effect for electrons, and of other recent quantum effects. For the effect involving a coherent superposition of beams of particles with opposite electromagnetic properties, by means of a tabletop experiment, the limit mph~=10-51g is achievable, improving by 6 orders of magnitude that derived
Analysis of Aharonov-Bohm effect due to time-dependent vector potentials
NASA Astrophysics Data System (ADS)
Lee, B.; Yin, E.; Gustafson, T. K.; Chiao, R.
1992-04-01
We analyze and propose a method to detect the Aharonov-Bohm effect due to time-varying vector potentials, specifically those arising from a coherent light source. We show that the effect is feasible for use as a light-intensity detector. The quantum limit of detection is that of a single photon. Such a system would be a quantum-nondemolition measurement since no photon absorption occurs.
Photon mass and quantum effects of the Aharonov-Bohm type
G. Spavieri; M. Rodriguez
2007-01-01
The magnetic field due to the photon rest mass m{sub ph} modifies the standard results of the Aharonov-Bohm effect for electrons, and of other recent quantum effects. For the effect involving a coherent superposition of beams of particles with opposite electromagnetic properties, by means of a tabletop experiment, the limit m{sub ph}10¹ g is achievable, improving by 6 orders of
Analysis of Aharonov-Bohm effect due to time-dependent vector potentials
B. Lee; E. Yin; T. K. Gustafson; R. Chiao
1992-01-01
We analyze and propose a method to detect the Aharonov-Bohm effect due to time-varying vector potentials, specifically those arising from a coherent light source. We show that the effect is feasible for use as a light-intensity detector. The quantum limit of detection is that of a single photon. Such a system would be a quantum-nondemolition measurement since no photon absorption
Anomalous Aharonov-Bohm Conductance Oscillations from Topological Insulator Surface States
Yi Zhang; Ashvin Vishwanath
2010-01-01
We study Aharonov-Bohm (AB) conductance oscillations arising from the surface states of a topological insulator nanowire, when a magnetic field is applied along its length. With strong surface disorder, these oscillations are predicted to have a component with anomalous period Phi0=hc\\/e, twice the conventional period. The conductance maxima are achieved at odd multiples of (1)\\/(2)Phi0, implying that a pi AB
Eckle, H.-P.; Johannesson, H.; Stafford, C. A.
2001-07-02
We study the persistent currents induced by both the Aharonov-Bohm and Aharonov-Casher effects in a one-dimensional mesoscopic ring coupled to a sidebranch quantum dot at Kondo resonance. For privileged values of the Aharonov-Bohm-Casher fluxes, the problem can be mapped onto an integrable model, exactly solvable by a Bethe ansatz. In the case of a pure magnetic Aharonov-Bohm flux, we find that the presence of the quantum dot has no effect on the persistent current. In contrast, the Kondo resonance interferes with the spin-dependent Aharonov-Casher effect to induce a current which, in the strong-coupling limit, is independent of the number of electrons in the ring.
Scattering of spin 1/2 particles by the 2+1 dimensional noncommutative Aharonov-Bohm potential
A. F. Ferrari; M. Gomes; C. A. Stechhahn
2007-08-28
In this work we study modifications in the Aharonov-Bohm effect for relativistic spin 1/2 particles due to the noncommutativity of spacetime in $2 + 1$ dimensions. The noncommutativity gives rise to a correction to the Aharonov-Bohm potential which is highly singular at the origin, producing divergences in a perturbative expansion around the usual solution of the free Dirac equation. This problem is surmounted by using a perturbative expansion around the exact solution of the \\textit{commutative} Aharonov-Bohm problem. We calculate, in this setting, the scattering amplitude and the corrections to the differential and total cross sections for a spin 1/2 particle, in the small-flux limit.
The Sagnac Effect in curved space-times from an analogy with the Aharonov-Bohm Effect
Matteo Luca Ruggiero
2005-10-28
In the context of the natural splitting, the standard relative dynamics can be expressed in terms of gravito-electromagnetic fields, which allow to formally introduce a gravito-magnetic Aharonov-Bohm effect. We showed elsewhere that this formal analogy can be used to derive the Sagnac effect in flat space-time as a gravito-magnetic Aharonov-Bohm effect. Here, we generalize those results to study the General Relativistic corrections to the Sagnac effect in some stationary and axially symmetric geometries, such as the space-time around a weakly gravitating and rotating source, Kerr space-time, G\\"{odel} universe and Schwarzschild space-time.
A charged particle in a homogeneous magnetic field accelerated by a time periodic Aharonov-Bohm flux
T. Kalvoda; P. Stovicek
2011-07-14
We consider a nonrelativistic quantum charged particle moving on a plane under the influence of a uniform magnetic field and driven by a periodically time-dependent Aharonov-Bohm flux. We observe an acceleration effect in the case when the Aharonov-Bohm flux depends on time as a sinusoidal function whose frequency is in resonance with the cyclotron frequency. In particular, the energy of the particle increases linearly for large times. An explicit formula for the acceleration rate is derived with the aid of the quantum averaging method, and then it is checked against a numerical solution with a very good agreement.
Tunable Pseudogap Kondo Effect and Quantum Phase Transitions in Aharonov-Bohm Interferometers
Dias Da Silva, Luis G [ORNL; Sandler, Nancy [Ohio University; Simon, Pascal [Ohio University; Ingersent, Kevin [University of Florida; Ulloa, Sergio E [Ohio University, Athens
2009-01-01
We study two quantum dots embedded in the arms of an Aharonov-Bohm ring threaded by a magnetic flux. This system can be described by an effective one-impurity Anderson model with an energy- and flux- dependent density of states. For specific values of the flux, this density of states vanishes at the Fermi energy, yielding a controlled realization of the pseudogap Kondo effect. The conductance and trans- mission phase shifts reflect a nontrivial interplay between wave interference and interactions, providing clear signatures of quantum phase transitions between Kondo and non-Kondo ground states.
Timothy H. Boyer
2005-06-23
The classical electromagnetic lag assocated with the Aharonov-Bohm phase shift is obtained by using a Darwin-Lagrangian analysis similar to that given by Coleman and Van Vleck to identify the puzzling forces of the Shockley-James paradox. The classical forces cause changes in particle velocities and so produce a relative lag leading to the same phase shift as predicted by Aharonov and Bohm and observed in experiments. An experiment is proposed to test for this lag aspect implied by the classical analysis but not present in the currently-accepted quantum topological description of the phase shift.
Scattering of spin-polarized electron in an Aharonov-Bohm potential
Khalilov, V.R. [Faculty of Physics, Moscow State University, 119899 Moscow (Russian Federation); Ho, C.-L. [Department of Physics, Tamkang University, Tamsui 25137, Taiwan (China)], E-mail: hcl@mail.tku.edu.tw
2008-05-15
The scattering of spin-polarized electrons in an Aharonov-Bohm vector potential is considered. We solve the Pauli equation in 3 + 1 dimensions taking into account explicitly the interaction between the three-dimensional spin magnetic moment of electron and magnetic field. Expressions for the scattering amplitude and the cross section are obtained for spin-polarized electron scattered off a flux tube of small radius. It is also shown that bound electron states cannot occur in this quantum system. The scattering problem for the model of a flux tube of zero radius in the Born approximation is briefly discussed.
Lai, Wenxi; Xing, Yunhui; Ma, Zhongshui
2013-05-22
Phase relaxation of electrons transferring through an electromechanical transistor is studied using the Aharonov-Bohm interferometer. Using the quantum master equation approach, the phase properties of an electron are numerically analyzed based on the interference fringes. The coherence of the electron is partially destroyed by its scattering on excited levels of the local nanomechanical oscillator. The transmission amplitudes with respect to two adjacent mechanical vibrational levels have a phase difference of ?. The character of the ? phase shift depends on the oscillator frequency only and is robust over a wide range of values of the applied voltage, tunneling length and damping rate of the mechanical oscillator. PMID:23615899
Loopholes in the interpretation of experiments on the Aharonov-Bohm effect
Herman Batelaan; Maria Becker
2015-07-02
The independence of the Aharonov-Bohm phase shift on particle velocity is one of its defining properties. The classical counterpart to this dispersionless behavior is the absence of forces along the direction of motion of the particle. A reevaluation of the experimental demonstration that forces are absent in the AB physical system is given, including previously unpublished data. It is shown that the debate on the presence or absence of forces is not settled, and an experiment searching for dispersionless forces is proposed.
On the possibility of transmitting signals by means of the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Ageev, A. N.; Chirkov, A. G.; Shalaev, B. N.; Markova, L. A.
2010-12-01
A mental experiment on the possible effect of an alternating current flowing along generating lines of an infinitely long cylinder on the interference diffraction pattern of microparticles has been considered. The possibility of exciting and detecting electromagnetic waves, which correspond to a zero electromagnetic field, and transmitting signals by means of the Aharonov-Bohm effect changing the phase of the electron wave function has been discussed. The results can be used in the design of a detector of an electromagnetic field that does not absorb photons of the detected radiation.
Aharonov-Bohm effects of radiative noise in linear dispersive media
NASA Astrophysics Data System (ADS)
Kurizki, G.
1991-05-01
It is suggested that the quantum uncertainty of cavity radiation is measurable via Aharonov-Bohm effects for electrons in a ring which is threaded by the magnetic cavity flux. When the electrons follow this oscillatory flux nearly adiabatically, and dissipation is negligible, the noise in the ring current should provide a quantum-nondemolition measure of the flux uncertainty. Unlike standard photodetection, such measurements should reveal the scaling of the flux uncertainty with the diamagnetic or dielectric index of the cavity medium, depending on the dimensions of the electron ring.
Zero modes in a system of Aharonov--Bohm solenoids on the Lobachevsky plane
V. A. Geyler; P. Stovicek
2005-09-01
We consider a spin 1/2 charged particle on the Lobachevsky plane subjected to a magnetic field corresponding to a discrete system of Aharonov-Bohm solenoids. Let $H^+$ and $H^-$ be the two components of the Pauli operator for spin up and down, respectively. We show that neither $H^+$ nor $H^-$ has a zero mode if the number of solenoids is finite. On the other hand, a construction is described of an infinite periodic system of solenoids for which either $H^+$ or $H^-$ has zero modes depending on the value of the flux carried by the solenoids.
Influence of Induced Charges in the Electric Aharonov-Bohm Effect
Rui-Feng Wang
2014-09-24
This paper states that the induced charge should not be neglected in the electric Aharonov-Bohm effect. If the induced charge is taken into account, the interference pattern of the moving charge will not change with the potential difference between the two metal tubes. It means that the scale potential itself can not affect the phase of the moving charge, and the true factor affecting the phase of the moving charge is the energy of the system including the moving charge and the induced charge.
Enhanced spin figure of merit in an Aharonov-Bohm ring with a double quantum dot
Zhou, Xingfei; Qi, Fenghua; Jin, Guojun, E-mail: gjin@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, Nanjing 210093 (China)
2014-04-21
We theoretically investigate the thermoelectric effects in an Aharonov-Bohm ring with a serially coupled double quantum dot embedded in one arm. An external magnetic field is perpendicularly applied to the two dots. Using the nonequilibrium Green's function method in the linear-response regime, we calculate the charge and spin figures of merit. When the energy levels of the two quantum dots are equal and the system is connected to two normal leads, a large spin figure of merit (Z{sub s}T???4.5) accompanying with a small charge figure of merit (Z{sub c}T???0) can be generated due to the remarkable bipolar effect. Further, when the system is connected to two ferromagnetic leads, the spin figure of merit can reach even a higher value about 9. Afterwards, we find that Z{sub s}T is enhanced while Z{sub c}T is reduced in the coaction of the Aharonov-Bohm flux and Rashba spin-orbit coupling. It is argued that the bipolar effect is positive (negative) to spin (charge) figure of merit in the presence of level detuning of the two quantum dots and intradot Coulomb interactions, respectively. Also, we propose a possible experiment to verify our results.
The Aharonov-Bohm Effect in a 3D topological insulator nanowire
NASA Astrophysics Data System (ADS)
Cho, Sungjae; Dellabetta, Brian; Yang, Alina; Schneeloch, John; Xu, Zhijun; Gu, Genda; Gilbert, Matthew; Mason, Nadya
2014-03-01
The three dimensional topological insulator (3D TI) is a new class of material having metallic surface states characterized by gapless Dirac dispersions and novel properties such as momentum-spin locking. A TI nanowire with an insulating bulk can be described as a hollow metallic cylinder, showing Aharonov-Bohm oscillations when a magnetic flux is threaded through the axis. The magneto-conductance of a TI nanowire near the Dirac point is expected to have a minimum at zero magnetic field and an oscillation period of one magnetic flux quantum, ? (due to a Berry phase of ? acquired by electron waves upon 2 ? rotation of electron spin around the surface of the nanowire). In this talk, we discuss magneto-conductance measurements of TI (Bi2Se3) nanowires, measured as the gate voltage is tuned through the Dirac point. The Aharonov-Bohm oscillations switch from a conductance maximum to a minimum at zero field as the Dirac point is approached, consistent with the existence of a Berry phase in the nanowire.
Aharonov-Bohm oscillations in a quasi-ballistic three-dimensional topological insulator nanowire.
Cho, Sungjae; Dellabetta, Brian; Zhong, Ruidan; Schneeloch, John; Liu, Tiansheng; Gu, Genda; Gilbert, Matthew J; Mason, Nadya
2015-01-01
Aharonov-Bohm oscillations effectively demonstrate coherent, ballistic transport in mesoscopic rings and tubes. In three-dimensional topological insulator nanowires, they can be used to not only characterize surface states but also to test predictions of unique topological behaviour. Here we report measurements of Aharonov-Bohm oscillations in (Bi1.33Sb0.67)Se3 that demonstrate salient features of topological nanowires. By fabricating quasi-ballistic three-dimensional topological insulator nanowire devices that are gate-tunable through the Dirac point, we are able to observe alternations of conductance maxima and minima with gate voltage. Near the Dirac point, we observe conductance minima for zero magnetic flux through the nanowire and corresponding maxima (having magnitudes of almost a conductance quantum) at magnetic flux equal to half a flux quantum; this is consistent with the presence of a low-energy topological mode. The observation of this mode is a necessary step towards utilizing topological properties at the nanoscale in post-CMOS applications. PMID:26158768
Energy Spectrum of a 2D Dirac Oscillator in the Presence of the Aharonov-Bohm Effect
N. Ferkous; A. Bounames
2008-01-30
We determine the energy spectrum and the corresponding eigenfunctions of a 2D Dirac oscillator in the presence of Aharonov-Bohm (AB) effect . It is shown that the energy spectrum depends on the spin of particle and the AB magnetic flux parameter. Finally, when the irregular solution occurs it is shown that the energy takes particular values. The nonrelativistic limit is also considered.
He Gao; Hong-Kang Zhao
2011-01-01
We have investigated the mesoscopic transport properties of an Aharonov-Bohm (AB) interferometer composed of a direct tunneling path and a resonant tunneling path incorporating a quantum dot (QD). The QD is perturbed by a rotating magnetic field (RMF) and an oscillating magnetic field (OMF). The nonresonant tunneling (NRT) path takes significant role in the spin and charge currents, and the
Andrade, F.M., E-mail: fmandrade@uepg.br [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900 Ponta Grossa-PR (Brazil); Silva, E.O., E-mail: edilbertoo@gmail.com [Departamento de Física, Universidade Federal do Maranhão, Campus Universitário do Bacanga, 65085-580 São Luís-MA (Brazil); Pereira, M., E-mail: marciano@uepg.br [Departamento de Matemática e Estatística, Universidade Estadual de Ponta Grossa, 84030-900 Ponta Grossa-PR (Brazil)
2013-12-15
In this work the bound state and scattering problems for a spin- 1/2 particle undergone to an Aharonov–Bohm potential in a conical space in the nonrelativistic limit are considered. The presence of a ?-function singularity, which comes from the Zeeman spin interaction with the magnetic flux tube, is addressed by the self-adjoint extension method. One of the advantages of the present approach is the determination of the self-adjoint extension parameter in terms of physics of the problem. Expressions for the energy bound states, phase-shift and S matrix are determined in terms of the self-adjoint extension parameter, which is explicitly determined in terms of the parameters of the problem. The relation between the bound state and zero modes and the failure of helicity conservation in the scattering problem and its relation with the gyromagnetic ratio g are discussed. Also, as an application, we consider the spin- 1/2 Aharonov–Bohm problem in conical space plus a two-dimensional isotropic harmonic oscillator. -- Highlights: •Planar dynamics of a spin- 1/2 neutral particle. •Bound state for Aharonov–Bohm systems. •Aharonov–Bohm scattering. •Helicity nonconservation. •Determination of the self-adjoint extension parameter.
Aharonov--Bohm E#ect in Scattering by a Chain of Point--like Magnetic Fields
Aharonov--Bohm E#ect in Scattering by a Chain of Point--like Magnetic Fields Hiroshi T. Ito the scattering by several point--like magnetic fields at large separation in two dimensions. We derive. Even if a magnetic field is compactly supported, the corresponding vector potential does
Analytical expression of Kondo temperature in quantum dot embedded in Aharonov-Bohm ring
2011-01-01
We theoretically study the Kondo effect in a quantum dot embedded in an Aharonov-Bohm ring, using the "poor man's" scaling method. Analytical expressions of the Kondo temperature TK are given as a function of magnetic flux ? penetrating the ring. In this Kondo problem, there are two characteristic lengths, Lc=?vF?|?˜0| and LK = ?vF = TK, where vF is the Fermi velocity and ?˜0 is the renormalized energy level in the quantum dot. The former is the screening length of the charge fluctuation and the latter is that of the spin fluctuation, i.e., size of Kondo screening cloud. We obtain diferent expressions of TK(?) for (i) Lc ? LK ? L, (ii) Lc ? L ? LK, and (iii) L ? Lc ? LK, where L is the size of the ring. TK is remarkably modulated by ? in cases (ii) and (iii), whereas it hardly depends on ? in case (i). PACS numbers: PMID:22112300
Chern-Simons theory of scalar particles and the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Boz, M.; Fainberg, V.; Pak, N. K.
1995-02-01
The S-matrix of the relativistic theory of charged scalar particles interacting via the Chern-Simons field is shown to be formally equivalent to the S-matrix of scalar QED in 2 + 1 dimensions in which the Feynman diagrams with external photon lines are excluded and the propagators of the Chern-Simons particles are substituted instead of the photon propagators. It is shown that the non-relativistic limit of the scattering amplitude of two anyons is also finite independently of the presence of the contact interaction, unlike the non-relativistic theory. It is found that for a certain value of the contact interaction, the scattering amplitude coincides with that of Aharonov-Bohm scattering in the same approximation.
Wave-packet rectification in nonlinear electronic systems: A tunable Aharonov-Bohm diode
Li, Yunyun; Zhou, Jun; Marchesoni, Fabio; Li, Baowen
2014-01-01
Rectification of electron wave-packets propagating along a quasi-one dimensional chain is commonly achieved via the simultaneous action of nonlinearity and longitudinal asymmetry, both confined to a limited portion of the chain termed wave diode. However, it is conceivable that, in the presence of an external magnetic field, spatial asymmetry perpendicular to the direction of propagation suffices to ensure rectification. This is the case of a nonlinear ring-shaped lattice with different upper and lower halves (diode), which is attached to two elastic chains (leads). The resulting device is mirror symmetric with respect to the ring vertical axis, but mirror asymmetric with respect to the chain direction. Wave propagation along the two diode paths can be modeled for simplicity by a discrete Schrödinger equation with cubic nonlinearities. Numerical simulations demonstrate that, thanks to the Aharonov-Bohm effect, such a diode can be operated by tuning the magnetic flux across the ring. PMID:24691462
Mesoscopic Transport Through a Quantum-Dot-Embedded Aharonov-Bohm Ring Threaded with AC Flux
NASA Astrophysics Data System (ADS)
Zhao, Hong-Kang
The electron transporting through a mesoscopic ring embedded with one quantum dot and threaded by dc and ac magnetic fluxes is investigated by employing the Keldysh nonequilibrium Green function technique. The tunneling current and differential conductance are derived to show the Aharonov-Bohm-like effect induced by external magnetic fluxes. The multi-channel ring and multi-level quantum dot system is studied. The quenching and nonmonotone effects versus the magnitude of ac flux are revealed in differential conductance. This signifies that at some values of ac flux, the tunneling current may be suppressed or enhanced. The differential conductance oscillation and I-V characteristics are studied numerically at zero temperature. The aperiodically nonmonotonical conductance versus the magnitude of ac flux, multi-channel negative differential conductance, photon-electron pump effect are also observed.
Polarized excitons in nanorings and the optical Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Govorov, A. O.; Ulloa, S. E.; Karrai, K.; Warburton, R. J.
2002-08-01
The quantum nature of matter lies in the wave function phases that accumulate while particles move along their trajectories. A prominent example is the Aharonov-Bohm phase, which has been studied in connection with the conductance of nanostructures. However, optical response in solids is determined by neutral excitations, for which no sensitivity to magnetic flux would be expected. We propose a mechanism for the topological phase of a neutral particle, a polarized exciton confined to a semiconductor quantum ring. We predict that this magnetic-field induced phase may strongly affect excitons in a system with cylindrical symmetry, resulting in switching between ``bright'' exciton ground states and novel ``dark'' states with nearly infinite lifetimes. Since excitons determine the optical response of semiconductors, the predicted phase can be used to tailor photon emission from quantum nanostructures.
Classical light analogue of the non-local Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Satapathy, Nandan; Pandey, Deepak; Mehta, Poonam; Sinha, Supurna; Samuel, Joseph; Ramachandran, Hema
2012-03-01
We demonstrate the existence of a non-local geometric phase in the intensity-intensity correlations of classical incoherent light, that is not seen in the lower-order correlations. This two-photon Pancharatnam phase was observed and modulated in a Mach-Zehnder interferometer. Using acousto-optic interaction, independent phase noise was introduced to light in the two arms of the interferometer to create two independent incoherent classical sources from laser light. The experiment is the classical optical analogue of the multi-particle Aharonov-Bohm effect. As the trajectory of light over the Poincaré sphere introduces a phase shift observable only in the intensity-intensity correlation, it provides a means of deflecting the two-photon wavefront, while having no effect on single photons.
Time-dependent electron transport through an Aharonov Bohm ring embedded with two quantum dots
NASA Astrophysics Data System (ADS)
Pan, Hui; Zhao, Li-Na; Lü, Rong
2008-08-01
The time-dependent electron transport through an Aharonov-Bohm ring embedded with two quantum dots in the presence of external microwave (MW) fields are investigated theoretically by using the nonequilibrium Green's function method. Whether the MW field can induce or suppress the Fano resonance depends on the part to which the field is applied. When the MW field is applied only to the two quantum dots, the photon-assisted Fano peaks appear at the sidebands of the original Fano peak. The existence of the original Fano peak or the photon-assisted ones can be controlled by the field strength. When the MW field is applied only to one lead, the original Fano peak is suppressed by the MW field, and the negative current caused by the electron-photon pump effects is found.
A possible interplay between electron beams and magnetic fluxes in the Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Wang, Rui-Feng
2015-04-01
Most studies on the magnetic Aharonov-Bohm (A-B) effect focus on the action exerted by the magnetic flux on the electron beam, but neglect the back-action exerted by the electron beam on the magnetic flux. This paper focuses on the latter, which is the electromotive force ?U across the solenoid induced by the time-dependent magnetic field of the electron beam. Based on the back-action analysis, we observe that the magnetic A-B effect arises owing to the interaction energy between the magnetic field of the electron beam and the magnetic field of the solenoid. We also demonstrate that the interpretation attributing the magnetic A-B effect to the vector potential violates the uncertainty principle.
Analytical expression of Kondo temperature in quantum dot embedded in Aharonov-Bohm ring.
Yoshii, Ryosuke; Eto, Mikio
2011-01-01
We theoretically study the Kondo effect in a quantum dot embedded in an Aharonov-Bohm ring, using the "poor man's" scaling method. Analytical expressions of the Kondo temperature TK are given as a function of magnetic flux ? penetrating the ring. In this Kondo problem, there are two characteristic lengths, Lc=?vF?|??0| and LK = ?vF = TK, where vF is the Fermi velocity and ??0 is the renormalized energy level in the quantum dot. The former is the screening length of the charge fluctuation and the latter is that of the spin fluctuation, i.e., size of Kondo screening cloud. We obtain diferent expressions of TK(?) for (i) Lc ? LK ? L, (ii) Lc ? L ? LK, and (iii) L ? Lc ? LK, where L is the size of the ring. TK is remarkably modulated by ? in cases (ii) and (iii), whereas it hardly depends on ? in case (i).PACS numbers: PMID:22112300
Thermoelectric effect in an Aharonov-Bohm ring with an embedded quantum dot
2012-01-01
Thermoelectric effect is studied in an Aharonov-Bohm interferometer with an embedded quantum dot (QD) in the Coulomb blockade regime. The electrical conductance, electron thermal conductance, thermopower, and thermoelectric figure-of-merit are calculated by using the Keldysh Green's function method. It is found that the figure-of-merit ZT of the QD ring may be quite high due to the Fano effect originated from the quantum interference effect. Moreover, the thermoelectric efficiency is sensitive to the magnitude of the dot-lead and inter-lead coupling strengthes. The effect of intradot Coulomb repulsion on ZT is significant in the weak-coupling regime, and then large ZT values can be obtained at rather high temperature. PMID:22369454
L. G. Mourokh; A. Yu. Smirnov; V. I. Puller; N. J. M. Horing
2002-01-01
We have analyzed electron relaxation dynamics in an isolated double-dot structure and have also examined lead-to-lead transport through a parallel double-dot threaded by Aharonov–Bohm (AB) magnetic flux. In the former case we determine the effect of an applied electric field on phonon-mediated electron relaxation. In the latter case we obtain the current–voltage characteristics and dependence of the current on AB
L. G. Mourokh; A. Yu. Smirnov; V. I. Puller; N. J. M. Horing
2002-01-01
We have analyzed electron relaxation dynamics in an isolated double-dot structure and have also examined lead-to-lead transport through a parallel double-dot threaded by Aharonov-Bohm (AB) magnetic flux. In the former case we determine the effect of an applied electric field on phonon-mediated electron relaxation. In the latter case we obtain the current-voltage characteristics and dependence of the current on AB
U. A. al-Binni; M. S. Shikakhwa
2005-01-01
In the presence of an external Aharonov–Bohm potential, we investigate the two QED processes of the emission of a bremsstrahlung\\u000a photon by an electron, and the production of an electron–positron pair by a single photon. Calculations are carried out using\\u000a the Born approximation within the framework of covariant perturbation theory to lowest non-vanishing order in ?. The matrix\\u000a element for
He Gao; Hong-Kang Zhao
2010-01-01
The commensurate photon-irradiated mesoscopic transport in a strongly correlated quantum dot (QD) embedded Aharonov–Bohm (AB) interferometer has been investigated. We focus our investigation on the dynamic Kondo and Fano cooperated effect affected by the double commensurate MWFs with q=?2\\/?1 being an arbitrary integer, where ?1 and ?2 are the two frequencies of the fields. The general tunneling current formula is
Charge and spin pumping effects in a single-dot Aharonov–Bohm ring with ferromagnetic leads
Hui Pan; Huai-Zhe Xu; Rong Lü
2010-01-01
The pumping of electrons through a single-dot Aharonov–Bohm ring attached to ferromagnetic leads are investigated theoretically by using the nonequilibrium Green's function method. It is found that the charge and spin pumping effects at zero-bias voltage can be produced by an oscillating electric field applied to the quantum dot. The pumped charge and spin currents through the single-dot ring are
Physical Optics, the Sagnac Effect, and the Aharonov-Bohm Effect in the Evans Unified Field Theory
Myron W. Evans
2004-01-01
A generally covariant and gauge invariant description of physical optics, the Sagnac effect, and the Aharonov-Bohm (AB) effect is developed using the appropriate phase factor for electrodynamics. The latter is a generally covariant development of the Dirac-Wu-Yang phase factor based on the generally covariant Stokes theorem. The Maxwell-Heaviside (MH) field theory fails to describe physical optics, interferometry, and topological phase
Phase switching in a voltage-biased Aharonov-Bohm interferometer
NASA Astrophysics Data System (ADS)
Puller, Vadim; Meir, Yigal
2008-03-01
Recent experiment [Sigrist et al., Phys. Rev. Lett. 98, 036805 (2007)] reported switches between 0 and ? in the phase of Aharonov-Bohm oscillations of the two-terminal differential conductance through a two-dot ring with increasing voltage bias. Using a simple model, where one of the dots contains multiple interacting levels, these findings are explained as a result of transport through the interferometer being dominated at different biases by quantum dot levels of different ``parity'' (i.e. the sign of the overlap integral between the dot state and the states in the leads). The redistribution of electron population between different levels with bias leads to the fact that the number of switching events is not necessarily equal to the number of dot levels, in agreement with experiment. For the same reason switching does not always imply that the parity of levels is strictly alternating. Lastly, it is demonstrated that the correlation between the first switching of the phase and the onset of the inelastic cotunneling, as well as the sharp (rather than gradual) change of phase when switching occurs, give reason to think that the present interpretation of the experiment is preferable to the one based on electrostatic AB effect.
Phase switching in a voltage-biased Aharonov-Bohm interferometer
NASA Astrophysics Data System (ADS)
Puller, Vadim I.; Meir, Yigal
2008-04-01
A recent experiment [M. Sigrist , Phys. Rev. Lett. 98, 036805 (2007)] reported switches between 0 and ? in the phase of Aharonov-Bohm (AB) oscillations of the two-terminal differential conductance through a two-dot ring with increasing voltage bias. Using a simple model, where one of the dots contains multiple interacting levels, these findings are explained as a result of transport through the interferometer being dominated at different biases by quantum dot levels of different “parities” (i.e., the sign of the overlap integral between the dot state and the states in the leads). The redistribution of electron population between different levels with bias leads to the fact that the number of switching events is not necessarily equal to the number of dot levels, in agreement with experiment. For the same reason, switching does not always imply that the parity of levels is strictly alternating. Lastly, it is demonstrated that the correlation between the first switching of the phase and the onset of the inelastic cotunneling, as well as the sharp (rather than gradual) change of phase when switching occurs, give reason to think that the present interpretation of the experiment is preferable to the one based on electrostatic AB effect.
Resonance and phase shift in an open Aharonov-Bohm ring with an embedded quantum dot.
Hedin, Eric R; Joe, Yong S; Satanin, Arkady M
2009-01-01
The transmission and phase properties of electron transport through a quantum dot (QD) with variable coupling to a third-terminal probe are investigated analytically for the case of the QD connected directly to source and drain reservoirs and when the QD is embedded in one arm of an Aharonov-Bohm (AB) ring. Using the tight-binding model, explicit analytical expressions of the transmission through the QD for each case are given. Expressions for the conductance with coupling to the third terminal, which breaks unitarity and phase-locking, are also given. It is shown that in a three-terminal interferometer the zero of the Fano resonance in the transmission moves off the real energy axis for finite values of the coupling parameter. The zero orbits around the pole in the complex energy plane as a function of magnetic flux through the ring, and can be returned to the real energy axis unless the coupling parameter exceeds a critical value. With the QD embedded in one arm of the AB ring, the electron transmission and the transmission phase, and the phase of the AB oscillations, are described in relation to the degree of coupling to the third-terminal probe which opens the interferometer. By tuning the degree of coupling to the probe, it is shown that the phase of the AB oscillations can be made to match the intrinsic phase of the QD, facilitating experimental characterization of the phase response of the QD. PMID:21817218
Beating of Aharonov-Bohm oscillations in a closed-loop interferometer
Jo, Sanghyun; Chang, Dong-In; Lee, Hu-Jong [Department of Physics, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); National Center for Nanomaterials Technology, Pohang 790-784 (Korea, Republic of); Khym, Gyong Luck; Kang, Kicheon [Department of Physics and Institute for Condensed Matter Theory, Chonnam National University, Gwangju 500-757 (Korea, Republic of); Chung, Yunchul [Department of Physics, Pusan National University, Busan 609-735 (Korea, Republic of); Mahalu, Diana; Umansky, Vladimir [Department of Condensed Matter Physics, Weizmann Institute of Science, Rehovot 76100 (Israel)
2007-07-15
One of the points at issue with closed-loop-type interferometers is beating in the Aharonov-Bohm (AB) oscillations. Recent observations suggest the possibility that the beating results from the Berry-phase pickup by the conducting electrons in materials with the strong spin-orbit interaction (SOI). In this study, we also observed beats in the AB oscillations in a gate-defined closed-loop interferometer fabricated on a GaAs/Al{sub 0.3}Ga{sub 0.7}As two-dimensional electron-gas heterostructure. Since this heterostructure has very small SOI, the picture of the Berry-phase pickup is ruled out. The observation of beats in this study, with the controllability of forming a single transverse subband mode in both arms of our gate-defined interferometer, also rules out the often-claimed multiple transverse subband effect. It is observed that nodes of the beats with an h/2e period exhibit a parabolic distribution for varying the side gate. These results are shown to be well interpreted, without resorting to the SOI effect, by the existence of two-dimensional multiple longitudinal modes in a single transverse subband. The Fourier spectrum of measured conductance, despite showing multiple h/e peaks with the magnetic-field dependence that are very similar to that from strong-SOI materials, can also be interpreted as the two-dimensional multiple-longitudinal-modes effect.
Aharonov-Bohm effect in non-uniform crater-like quantum dot with double rim
NASA Astrophysics Data System (ADS)
García, L. F.; Revinova, S. Yu.; Mikhailov, I. D.
2015-07-01
We study electron energies in a double concentric quantum ring with anisotropy in the rims heights in the presence of the external magnetic field applied along the symmetry axis. To this end, we consider a model in which the thickness grows linearly from the axis up to the inner rim with a slope different from one between the inner and the outer rims. The anisotropy in the rims heights originated by the presence in the structure of various valleys we simulate by periodic dependence of the slope on the radial direction. We show that the wave functions of the electron confined in such structure can be found analytically if the slopes in all radial directions are the same, and by using a simple exact diagonalization procedure otherwise. The behavior of the electron energies as functions of the magnetic field, rings radii and rims heights, as well as the number of the valleys and their depths is consistently described with our formalism. The entanglement of the states with different radial and orbital quantum numbers, the period and the amplitude of the Aharonov-Bohm oscillations are very sensible to any variations of the rims heights.
Slow photons as charged quasi-particles, and photonic Aharonov-Bohm effect
NASA Astrophysics Data System (ADS)
Marzlin, Karl-Peter; Appel, Juergen; Lvovsky, Alexander
2007-06-01
Recently we have proposed the method of Raman Adiabatic Transfer of Optical States (RATOS) to manipulate the optical state of light. A four-level atomic medium in double-? configuration is interacting with two pump fields and a signal photon with very slow group velocity. An adiabatic change in time of the pump fields can then generate a slow photon in a superposition of different frequencies. Here we theoretically analyze the influence of an adiabatic change in the spatial form of the pump fields. We demonstrate that the signal photon then behaves like a charged quasi-particle: in paraxial approximation its dynamics is governed by a Schr"odinger-like equation that includes a scalar and a vector potential whose form is determined by the shape of the pump fields. We suggest pump field configurations that generate potentials corresponding to a constant electric and a constant magnetic field. Furthermore we devise a scheme of pump fields that generates a vector potential of Aharonov-Bohm type which induces a topological phase shift for slow photons.
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms.
Huo, Ming-Xia; Nie, Wei; Hutchinson, David A W; Kwek, Leong Chuan
2014-01-01
Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a "hairline" solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions. PMID:25103877
NASA Astrophysics Data System (ADS)
Wang, Dehua
2014-09-01
The Aharonov–Bohm (AB) effect in the photodetachment microscopy of the H? ions in an electric field has been studied on the basis of the semiclassical theory. After the H? ion is irradiated by a laser light, they provide a coherent electron source. When the detached electron is accelerated by a uniform electric field, two trajectories of a detached electron which run from the source to the same point on the detector, will interfere with each other and lead to an interference pattern in the photodetachment microscopy. After the solenoid is electrified beside the H? ion, even though no Lorentz force acts on the electron outside the solenoid, the photodetachment microscopy interference pattern on the detector is changed with the variation in the magnetic flux enclosed by the solenoid. This is caused by the AB effect. Under certain conditions, the interference pattern reaches the macroscopic dimensions and could be observed in a direct AB effect experiment. Our study can provide some predictions for the future experimental study of the AB effect in the photodetachment microscopy of negative ions.
A solenoidal synthetic field and the non-Abelian Aharonov-Bohm effects in neutral atoms
NASA Astrophysics Data System (ADS)
Huo, Ming-Xia; Nie, Wei; Hutchinson, David A. W.; Kwek, Leong Chuan
2014-08-01
Cold neutral atoms provide a versatile and controllable platform for emulating various quantum systems. Despite efforts to develop artificial gauge fields in these systems, realizing a unique ideal-solenoid-shaped magnetic field within the quantum domain in any real-world physical system remains elusive. Here we propose a scheme to generate a ``hairline'' solenoid with an extremely small size around 1 micrometer which is smaller than the typical coherence length in cold atoms. Correspondingly, interference effects will play a role in transport. Despite the small size, the magnetic flux imposed on the atoms is very large thanks to the very strong field generated inside the solenoid. By arranging different sets of Laguerre-Gauss (LG) lasers, the generation of Abelian and non-Abelian SU(2) lattice gauge fields is proposed for neutral atoms in ring- and square-shaped optical lattices. As an application, interference patterns of the magnetic type-I Aharonov-Bohm (AB) effect are obtained by evolving atoms along a circle over several tens of lattice cells. During the evolution, the quantum coherence is maintained and the atoms are exposed to a large magnetic flux. The scheme requires only standard optical access, and is robust to weak particle interactions.
NASA Astrophysics Data System (ADS)
Avossevou, Gabriel Y. H.; Ahounou, Bernadin D.
2014-09-01
In this paper we study the stationary scattering problem of the Aharonov-Bohm (AB) effect. To achieve this goal we construct a Hamiltonian from the most general representations of the Heisenberg algebra. Such representations are defined on a non-simply-connected manifold which we set as the flat circular annulus. By means of the von Neumann's self-adjoint extensions formalism, the scattering data are then provided. No solenoid is considered in this paper. The corresponding Hamiltonian is based on a topological quantum degree of freedom inherent in such representations. This variable stands for the magnetic vector gauge potential at quantum level. Our outcomes confirm the topological nature of this effect.
Aharonov-Bohm effect on AdS_2 and nonlinear supersymmetry of reflectionless Poschl-Teller system
Francisco Correa; Vit Jakubsky; Mikhail S. Plyushchay
2009-03-29
We explain the origin and the nature of a special nonlinear supersymmetry of a reflectionless Poschl-Teller system by the Aharonov-Bohm effect for a nonrelativistic particle on the AdS_2. A key role in the supersymmetric structure appearing after reduction by a compact generator of the AdS_2 isometry is shown to be played by the discrete symmetries related to the space and time reflections in the ambient Minkowski space. We also observe that a correspondence between the two quantum non-relativistic systems is somewhat of the AdS/CFT holography nature.
NASA Astrophysics Data System (ADS)
Kalinski, Maciej
1998-03-01
We study the influence of a weak magnetic field on time evolution of a quantum state that is a coherent superposition of two counter-rotating Trojan wave packets in a linearly polarized electromagnetic field. We demonstrate that both the interference pattern of the electron probability density and differential cross section for half-cycle pulse ionization exhibit periodic modulation as a function of magnetic flux cutting the plane of packet motion. The shift is proportional to the magnetic flux in a way characteristic for the Aharonov-Bohm effect.
Timothy H. Boyer
2014-08-26
A new classical electromagnetic analysis is presented suggesting that the Aharonov-Bohm phase shift is overwhelmingly likely to arise from a classical lag effect based upon classical electromagnetic forces. The analysis makes use of several aspects of classical electromagnetic theory which are unfamiliar to most physicists, including the Darwin Lagrangian, acceleration-based electric fields, internal electromagnetic momentum in a magnet, and a magnet model involving at least three mutually-interacting particles. Only when the acceleration-based electric forces acting on the passing charge are included do we find consistency with all the relativistic conservation laws: energy, linear momentum, angular momentum, and constant center-of-mass velocity. The electric forces on the passing charge lead to a lag effect which accounts quantitatively for the Aharonov-Bohm phase shift. Thus the classical analysis strongly suggests that the Aharonov-Bohm phase shift (observed when electrons pass a long solenoid which corresponds to a line of magnetic dipoles) is the analogue of the Matteucci-Pozzi phase shift (observed when electrons pass a line of electric dipoles). The classical electromagnetic analysis suggests experiments to distinguish the proposed classical-based lag effect from the presently accepted view that the Aharonov-Bohm phase shift is a quantum topological effect arising from magnetic fluxes in the absence of classical electromagnetic forces.
Bruno, Patrick
2012-06-15
The (Berry-Aharonov-Anandan) geometric phase acquired during a cyclic quantum evolution of finite-dimensional quantum systems is studied. It is shown that a pure quantum state in a (2J+1)-dimensional Hilbert space (or, equivalently, of a spin-J system) can be mapped onto the partition function of a gas of independent Dirac strings moving on a sphere and subject to the Coulomb repulsion of 2J fixed test charges (the Majorana stars) characterizing the quantum state. The geometric phase may be viewed as the Aharonov-Bohm phase acquired by the Majorana stars as they move through the gas of Dirac strings. Expressions for the geometric connection and curvature, for the metric tensor, as well as for the multipole moments (dipole, quadrupole, etc.), are given in terms of the Majorana stars. Finally, the geometric formulation of the quantum dynamics is presented and its application to systems with exotic ordering such as spin nematics is outlined. PMID:23004240
Fano effect in the Andreev reflection of the Aharonov-Bohm-Fano ring with Majorana bound states
NASA Astrophysics Data System (ADS)
Jiang, Cui; Zheng, Yi-Song
2015-06-01
The Andreev reflection in an Aharonov-Bohm-Fano ring induced by Majorana bound states (MBSs) is theoretically investigated. We find that compared with the Fano effect in the normal electron tunneling process, the Fano effect here is more determined by the structural parameters, i.e., the quantum dot level, the dot-MBS coupling, and the dot-MBS and MBS-lead couplings. By transforming the ring into its Nambu representation, we present a comprehensive analysis about the quantum interference in the Andreev reflection, and then explain the reason for the occurrence of the Fano effect. These results will be helpful for understanding the quantum interference in the MBS-assisted Andreev reflection.
NASA Astrophysics Data System (ADS)
Akbar Rajabi, Ali; Hamzavi, Majid
2013-01-01
The Cornellpotential consists of linear and Coulomb potentials, i.e. - a/ r+ br, and has attracted a great deal of attention in particle physics. In this article, we study the energy levels and the wave function for an arbitrary m-state in the two-dimensional (2D) Klein-Gordon (KG) equation with the unequal scalar-vector Cornell potentials under the influence of strong external uniform magnetic and Aharonov-Bohm (AB) flux fields perpendicular to the plane where the interacting particles are confined. We use the wave function ansatz method to solve the radial problem of the KG equation with the Cornell potential. We obtain the energy levels in the absence of external fields and also find the energy levels of the familiar Coulomb and harmonic oscillator potentials.
Ren, S L; Heremans, J J; Gaspe, C K; Vijeyaragunathan, S; Mishima, T D; Santos, M B
2013-10-30
Low-temperature Aharonov-Bohm oscillations in the magnetoresistance of mesoscopic interferometric rings patterned on an InGaAs/InAlAs heterostructure are investigated for their dependence on excitation current and temperature. The rings have an average radius of 650 nm, and a lithographic arm width of 300 nm, yielding pronounced interference oscillations over a wide range of magnetic fields. Apart from a current and temperature dependence, the oscillation amplitude also shows a quasi-periodic modulation with applied magnetic field. The phase coherence length is extracted by analysis of the fundamental and higher Fourier components of the oscillations, and by direct analysis of the amplitude and its dependence on parameters. It is concluded that the Thouless energy forms the measure of excitation energies for quantum decoherence. The amplitude modulation finds an explanation in the effect of the magnetic flux threading the finite width of the interferometer arms. PMID:24096892
Charge and spin pumping effects in a single-dot Aharonov-Bohm ring with ferromagnetic leads
NASA Astrophysics Data System (ADS)
Pan, Hui; Xu, Huai-Zhe; Lü, Rong
2010-11-01
The pumping of electrons through a single-dot Aharonov-Bohm ring attached to ferromagnetic leads are investigated theoretically by using the nonequilibrium Green's function method. It is found that the charge and spin pumping effects at zero-bias voltage can be produced by an oscillating electric field applied to the quantum dot. The pumped charge and spin currents through the single-dot ring are analyzed for two cases: (i) the single-dot ring is connected with two ferromagnetic leads and (ii) the single-dot ring is connected with a ferromagnetic and a normal-metal lead. For the former case, a pure spin current can be generated due to the photon-assisted tunneling effects. For the latter case, both the charge and spin current can be pumped in opposite directions. The control of the pumped spin and charge current by using the magnetic flux through the ring is also discussed.
NASA Astrophysics Data System (ADS)
Morinaga, Atsuo; Nanri, Kota
2012-08-01
Using a magnetic-field-insensitive two-photon transition, the phase shift of atomic interference fringes and the frequency shift of the resonance spectrum were examined for a noncyclic rotation of a magnetic field during the interrogation time of an atom interferometer. We observed a phase shift proportional to the rotation angle of the magnetic field when the initial state and the final state were subjected to interference. We confirmed that the phase shift is equivalent to the scalar Aharonov-Bohm phase due to the geometrical potential. On the other hand, we demonstrated that the noncyclic Berry phase defined by the geodesic gauge is measurable using a strategy that the magnetic field rapidly returns to the initial direction during the interrogation time of the atom interferometer.
Georg Schütz; Alexander Rembold; Andreas Pooch; Henrike Prochel; Alexander Stibor
2014-12-19
We propose an experiment for the first proof of the type I electric Aharonov-Bohm effect in an ion interferometer for hydrogen. The performances of three different beam separation schemes are simulated and compared. The coherent ion beam is generated by a single atom tip (SAT) source and separated by either two biprisms with a quadrupole lens, two biprisms with an einzel-lens or three biprisms. The beam path separation is necessary to introduce two metal tubes that can be pulsed with different electric potentials. The high time resolution of a delay line detector allows to work with a continuous ion beam and circumvents the pulsed beam operation as originally suggested by Aharonov and Bohm. We demonstrate, that the higher mass and therefore lower velocity of ions compared to electrons combined with the high expected SAT ion emission puts the direct proof of this quantum effect for the first time into reach of current technical possibilities. Thereby a high coherent ion detection rate is crucial to avoid long integration times that allow the influence of dephasing noise from the environment. We can determine the period of the expected matter wave interference pattern and the signal on the detector by determining the superposition angle of the coherent partial beams. Our simulations were tested with an electron interferometer setup and agree with the experimental results. We determine the separation scheme with three biprisms to be most efficient and predict a total signal acquisition time of only 80 s to measure a phase shift from 0 to 2$\\pi$ due to the electric Aharonov-Bohm effect.
Timothy H. Boyer
2001-07-04
A fundamentally new understanding of the classical electromagetic interaction of a point charge and a magnetic moment through order second order in 1/c is suggested. This relativistic analysis connects together hidden momentum in magnets, Solem's strange polarization of the classical hydrogen atom, and the Aharonov-Bohm Phase shift. We use a relativistic magnetic moment model consisting of many superimposed classical hydrogen atoms interacting through the Darwin Lagrangian with an external charge but not with each other. The analysis of Solem regarding the strange polarization of the classical hydrogen atom is seen to give a fundamentally different mechanism for the electric field of the passing charge to change the magnetic moment. The changing magnetic moment leads to an electric force back at the point charge which i)is second order in 1/c, ii)depends upon the magnetic dipole moment, changing sign with the dipole moment, iii)is odd in the charge q of the passing charge, and iv)reverses sign for charges passing on opposite sides of the magnetic moment. We suggest that a realistic multi-particle magnetic moment involves a changing magnetic moment which keeps the electromagnetic field momentum constant. This means also that the magnetic moment does not allow a significant shift in its internal center of energy. This criterion also implies that the Lorentz forces on the charged particle and on the point charge are equal and opposite and that the center of energy of each moves according to Newton's second law where the force is exactly the Lorentz force. Finally, we note that the results and suggestion given here are precisely what are needed to explain both the Aharonov-Bohm phase shift and the Aharonov-Casher phase shift as arising from classical electromagnetic forces.
Lev Vaidman; Mark Dennis; Sandu Popescu
2010-01-01
This is a call for contributions to a special issue of Journal of Physics A: Mathematical and Theoretical dedicated to the subject of quantum phases and highlighting the impact of the discovery of the Aharonov--Bohm effect and of the Berry phase across physics. Researchers working in the area are invited to submit papers of original research to this issue. Editorial
NASA Astrophysics Data System (ADS)
Numazaki, Kazuya; Imai, Hiromitsu; Morinaga, Atsuo
2010-03-01
The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 ?T was measured as the scalar Aharonov-Bohm phase by two-photon stimulated Raman atom interferometry. The ac Stark effect of the Raman pulse was canceled out by adopting an appropriate intensity ratio of two photons in the Raman pulse. The Ramsey fringes for the pulse separation of 7 ms were obtained with a phase uncertainty of ?/200 rad. The nondispersive feature of the scalar Aharonov-Bohm phase was clearly demonstrated through 18 fringes with constant amplitude. The Breit-Rabi formula of the sodium clock transition was verified to be ??=(0.222±0.003)×1012×B1.998±0.004 in a magnetic field of less than 50 ?T.
Numazaki, Kazuya; Imai, Hiromitsu; Morinaga, Atsuo [Department of Physics, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda-shi, Chiba 278-8510 (Japan)
2010-03-15
The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 {mu}T was measured as the scalar Aharonov-Bohm phase by two-photon stimulated Raman atom interferometry. The ac Stark effect of the Raman pulse was canceled out by adopting an appropriate intensity ratio of two photons in the Raman pulse. The Ramsey fringes for the pulse separation of 7 ms were obtained with a phase uncertainty of {pi}/200 rad. The nondispersive feature of the scalar Aharonov-Bohm phase was clearly demonstrated through 18 fringes with constant amplitude. The Breit-Rabi formula of the sodium clock transition was verified to be {Delta}{nu}=(0.222{+-}0.003)x10{sup 12}xB{sup 1.998{+-}0.004} in a magnetic field of less than 50 {mu}T.
Kazuya Numazaki; Hiromitsu Imai; Atsuo Morinaga
2010-01-01
The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 muT was measured as the scalar Aharonov-Bohm phase by two-photon stimulated Raman atom interferometry. The ac Stark effect of the Raman pulse was canceled out by adopting an appropriate intensity ratio of two photons in the Raman pulse. The Ramsey fringes for
Kazuya Numazaki; Hiromitsu Imai; Atsuo Morinaga
2010-01-01
The second-order Zeeman effect of the sodium clock transition in a weak magnetic field of less than 50 Î¼T was measured as the scalar Aharonov-Bohm phase by two-photon stimulated Raman atom interferometry. The ac Stark effect of the Raman pulse was canceled out by adopting an appropriate intensity ratio of two photons in the Raman pulse. The Ramsey fringes for
NASA Astrophysics Data System (ADS)
Gao, He; Zhao, Hong-Kang
2010-01-01
The commensurate photon-irradiated mesoscopic transport in a strongly correlated quantum dot (QD) embedded Aharonov-Bohm (AB) interferometer has been investigated. We focus our investigation on the dynamic Kondo and Fano cooperated effect affected by the double commensurate MWFs with q=?/? being an arbitrary integer, where ? and ? are the two frequencies of the fields. The general tunneling current formula is derived by employing the nonequilibrium Green's function technique, and the different photon absorption and emission processes induced nonlinear properties have been studied to compare with the single-field system where q=0. Our numerical calculations are performed for the special cases with two commensurate fields possessing q=1,2. The Kondo peak can be suppressed to be a Kondo valley for the case where the commensurate number q=1, and the Fano asymmetric structure exhibits in the differential conductance quite evidently. Different commensurate number q contributes different photon absorption and emission effects. However, the conductance for the case of q=2 possesses more peaks and heavier asymmetric structure than the situations of q=0,1. The enhancement of satellite peaks behaves quite differently for the two cases with q=1, and q=2. The asymmetric peak-valley structure is adjusted by the gate voltage, commensurate MWFs, AB flux, source-drain bias, and non-resonant tunneling strength to form novel Fano and Kondo resonant tunneling.
NASA Astrophysics Data System (ADS)
Gao, He; Zhao, Hong-Kang
We have investigated the mesoscopic transport properties of an Aharonov-Bohm (AB) interferometer composed of a direct tunneling path and a resonant tunneling path incorporating a quantum dot (QD). The QD is perturbed by a rotating magnetic field (RMF) and an oscillating magnetic field (OMF). The nonresonant tunneling (NRT) path takes significant role in the spin and charge currents, and the Fano profiles display in the currents due to the modification of NRT strength. The spin current exhibits completely different behaviors as the source-drain bias eV = 0 and eV?0. The spin current is symmetric versus gate voltage when the source-drain bias eV = 0; however, it becomes asymmetric Fano-line shape resulting from the interference effect when eV?0. The OMF induced photon-assisted tunneling is quite different from the ones induced by the oscillating electric field and RMF. The tunnel currents vary dramatically with the evolution of the AB magnetic flux, and the Fano-type spin and charge currents are adjusted by OMF, RMF, AB flux, gate voltage, the source-drain bias, as well as the NRT strength to generate novel Fano-type photon-assisted spin and charge currents.
Miyamoto, Satoru; Ishikawa, Toyofumi; Eto, Mikio; Itoh, Kohei M. [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Moutanabbir, Oussama [School of Fundamental Science and Technology, Keio University, 3-14-1 Hiyoshi, Kohoku-ku, Yokohama 223-8522 (Japan); Max Planck Institute of Microstructure Physics, Weinberg 2, Halle (Saale), 06120 (Germany); Haller, Eugene E. [Lawrence Berkeley National Laboratory and UC Berkeley, 1 Cyclotron Road, Berkeley, California 94720 (United States); Sawano, Kentarou; Shiraki, Yasuhiro [Research Center for Silicon Nano-Science, Advanced Research Laboratories, Tokyo City University, 8-15-1 Todoroki, Setagaya-ku, Tokyo 158-0082 (Japan)
2010-08-15
We report on a magnetophotoluminescence study of isotopically pure {sup 70}Ge/Si self-assembled type-II quantum dots. Oscillatory behaviors attributed to the Aharonov-Bohm effect are simultaneously observed for the emission energy and intensity of excitons subject to an increasing magnetic field. When the magnetic flux penetrates through the ringlike trajectory of an electron moving around each quantum dot, the ground state of an exciton experiences a change in its angular momentum. Our results provide the experimental evidence for the phase coherence of localized electron wave functions in group-IV Ge/Si self-assembled quantum structures.
The optical Aharonov-Bohm effect and magneto-optical properties in type-II quantum dots
NASA Astrophysics Data System (ADS)
Whiteside, Vincent Ryan
We present a detailed experimental study of the magneto-optical properties of type-II quantum dots (QDs) in: (1) ZnTe/ZnSe superlattices grown by Molecular Beam Epitaxy (MBE)---these Zn(SeTe) QDs evolve from Te-clustering in the ZnSe matrix during growth; and (2) diluted magnetic semiconductor, (ZnMn)Se, QDs in a ZnSe matrix produced by migration enhanced epitaxy. In case (1) the Zn(SeTe) QDs display large and robust (with temperature) oscillations as a function of magnetic field in both the photoluminescence energy and intensity as a result of the optical Aharonov-Bohm effect. The large strength of these oscillations is attributed to a combination of the type-II symmetry and the columnar geometry of the structures; the oscillations persist until 180K. The type-II diluted magnetic semiconductor, (ZnMn)Te quantum dots display similar oscillatory effects in the emission intensity. Interestingly, the coherence of the Aharonov-Bohm phase in these magnetic dots is strongly related to the spin polarization of the system due to the Mn-exciton exchange interaction as shown by the disappearance of the oscillations at low magnetic fields. The enhanced coherence at high fields, which leads to strong oscillations in intensity, is attributed to removal of magnetic disorder by the applied magnetic field. While the magnetic nature of the QDs is clear from the polarization measurements there is the seemingly contradictory behavior of a very small Zeeman shift for material that has a corresponding large Zeeman shift for the comparable composition of bulk (ZnMn)Te. More importantly, a red shift greater than 30 meV is observed in the peak energy of the PL as function of time after excitation with a picosecond pulse. These results can be explained by postulating formation of bound magnetic polarons in the QDs. The overall red shift is identified as the magnetic polaron binding energy, EMP; it is roughly independent of temperature, persisting up to 150K. The large MP binding energy is apparently contradictory to the small observed Zeeman splitting and the temperature dependence of the optical polarization in the steady state. These apparently contradictory properties are interpreted in terms of a model that explains the temperature dependence as well as the polarization and Zeeman energy splitting, while fully taking into account the polaron formation energy. The model is based on the hole-Mn and the Mn-Mn exchange coupling and their role in the magnetic polaron formation with a crucial aspect being the formation of an antiferromagnetically ordered state of the Mn spin system in each of the QDs in the absence of photoinjected holes.
NASA Astrophysics Data System (ADS)
Tu, Matisse Wei-Yuan; Aharony, Amnon; Zhang, Wei-Min; Entin-Wohlman, Ora
2014-10-01
The spin-resolved nonequilibrium real-time electron transport through a double-quantum-dot (DQD) Aharonov-Bohm (AB) interferometer with spin-orbit interaction (SOI) is explored. The SOI and AB interference in the real-time dynamics of spin transport is expressed by effective magnetic fluxes. Analytical formulas for the time-dependent currents, for initially unpolarized spins, are presented. In many cases, there appear spin currents in the electrodes, for which the spins in each electrode are polarized along characteristic directions, predetermined by the SOI parameters and by the geometry of the system. Special choices of the system parameters yield steady-state currents in which the spins are fully polarized along these characteristic directions. The time required to reach this steady state depends on the couplings of the DQD to the leads. The magnitudes of the currents depend strongly on the SOI-induced effective fluxes. Without the magnetic flux, the spin-polarized current cannot be sustained to the steady states, due to the phase rigidity for this system. For a nondegenerate DQD, transient spin transport can be produced by the sole effects of SOI. We also show that one can extract the spin-resolved currents from measurements of the total charge current.
Matisse Wei-Yuan Tu; Amnon Aharony; Wei-Min Zhang; Ora Entin-Wohlman
2014-10-02
The spin-resolved non-equilibrium real-time electron transport through a double-quantum-dot (DQD) Aharonov-Bohm (AB) interferometer with spin-orbit interaction (SOI) is explored. The SOI and AB interference in the real-time dynamics of spin transport is expressed by effective magnetic fluxes. Analytical formulae for the time-dependent currents, for initially unpolarized spins, are presented. In many cases, there appear spin currents in the electrodes, for which the spins in each electrode are polarized along characteristic directions, pre-determined by the SOI parameters and by the geometry of the system. Special choices of the system parameters yield steady-state currents in which the spins are fully polarized along these characteristic directions. The time required to reach this steady state depends on the couplings of the DQD to the leads. The magnitudes of the currents depend strongly on the SOI-induced effective fluxes. Without the magnetic flux, the spin-polarized current cannot be sustained to the steady states, due to the phase rigidity for this system. For a non-degenerate DQD, transient spin transport can be produced by the sole effects of SOI. We also show that one can extract the spin-resolved currents from measurements of the total charge current.
R. Y. Chiao
2012-06-23
The flux as measured by the Josephson effect in a SQUID-like configuration with a ferromagnetic core inserted into its center, is shown to be sensitive to the vector potential arising from the central ferromagnetic core, even when the core is covered with a superconducting material that prevents any magnetic field lines from ever reaching the perimeter of the SQUID-like configuration. This leads to a macroscopic, Aharonov-Bohm-like effect that is observable in an asymmetric hysteresis loop in the response of the SQUID-like configuration to an externally applied magnetic field.
Raymond Chiao
2012-05-28
A novel kind of nonlocal, macroscopic Aharonov-Bohm effect involving two topologically linked superconducting rings made out of two different materials, namely, lead and tin, is suggested for experimental observation, in which the lead ring is a torus containing a core composed of permanently magnetized ferromagnetic material. It is predicted that the remnant fields in a hysteresis loop induced by the application of a magnetic field imposed by a large external pair of Helmholtz coils upon the tin ring, will be asymmetric with respect to the origin of the loop. An appendix based on Feynman's path-integral principle is the basis for these predictions.
Aharonov-Bohm effect for an exciton
NASA Astrophysics Data System (ADS)
Römer, R. A.; Raikh, M. E.
2000-09-01
We theoretically study exciton absorption on a ring threaded by a magnetic flux. For the case when the attraction between an electron and a hole is short ranged, we obtain an exact solution of the problem. We demonstrate that, despite the electrical neutrality of the exciton, both the spectral position of the exciton peak in the absorption and the corresponding oscillator strength oscillate with magnetic flux with a period ?0-the universal flux quantum. The origin of the effect is the finite probability for electron and hole, created by a photon at the same point, to tunnel in the opposite directions and meet each other on the opposite side of the ring.
Aharonov-Bohm effect for an exciton
R. A. Romer; M. E. Raikh
2000-01-01
We study theoretically the exciton absorption on a ring shreded by a magnetic\\u000aflux. For the case when the attraction between electron and hole is\\u000ashort-ranged we get an exact solution of the problem. We demonstrate that,\\u000adespite the electrical neutrality of the exciton, both the spectral position of\\u000athe exciton peak in the absorption, and the corresponding oscillator strength
Aharonov-Bohm effect for an exciton
R. A. Römer; M. E. Raikh
2000-01-01
We theoretically study exciton absorption on a ring threaded by a magnetic flux. For the case when the attraction between an electron and a hole is short ranged, we obtain an exact solution of the problem. We demonstrate that, despite the electrical neutrality of the exciton, both the spectral position of the exciton peak in the absorption and the corresponding
Exciton Aharonov-Bohm Effect in Embedded Nanostructures
Zimmermann, Roland
within the envelope function formalism and applying the effective mass approximation. Since the nanoring is embedded in a narrow quantum well, the single sublevel approxima- tion holds. In-plane cylindrical symmetry wide Gao.51Ino.49P quantum well sandwiched between AlAs barriers. Due to the different lattice
Radiative corrections to the Aharonov-Bohm scattering
L. C. de Albuquerque; M. Gomes; A. J. da Silva
1999-01-01
We consider the scattering of relativistic electrons from a thin magnetic\\u000aflux tube and perturbatively calculate the order $\\\\alpha$, radiative\\u000acorrection, to the first order Born approximation. We show also that the second\\u000aorder Born amplitude vanishes, and obtain a finite inclusive cross section for\\u000athe one-body scattering which incorporates soft photon bremsstrahlung effects.\\u000aMoreover, we determine the radiatively corrected
The Aharonov-Bohm effect for an exciton
R. A. Römer; M. E. Raikh
2000-01-01
We study theoretically the exciton absorption (luminescence) of a ring-like quantum dot shreded by a magnetic flux. We consider the limit when the width of the ring is smaller than the excitonic Bohr radius a_B. We demonstrate that, despite the electrical neutrality of the exciton, both the spectral position of the exciton peak in the absorption (luminescence), and the corresponding
Radiative corrections to the Aharonov-Bohm scattering
L. C. de Albuquerque; M. Gomes; A. J. da Silva
2000-01-01
We consider the scattering of relativistic electrons from a thin magnetic flux tube and perturbatively calculate the order alpha radiative correction to the first order Born approximation. We show also that the second order Born amplitude vanishes, and obtain a finite inclusive cross section for the one-body scattering which incorporates soft photon bremsstrahlung effects. Moreover, we determine the radiatively corrected
The Aharonov-Bohm effect for an exciton
NASA Astrophysics Data System (ADS)
Römer, R. A.; Raikh, M. E.
2000-03-01
We study theoretically the exciton absorption (luminescence) of a ring-like quantum dot shreded by a magnetic flux. We consider the limit when the width of the ring is smaller than the excitonic Bohr radius a_B. We demonstrate that, despite the electrical neutrality of the exciton, both the spectral position of the exciton peak in the absorption (luminescence), and the corresponding oscillator strength oscillate with magnetic flux with a period ?0 --- the universal flux quantum. Assuming that the attraction between electron and hole is short-ranged we find analytically the functional form of these oscillations for both quantities.^1 This enables us to trace the magnitude of the effect with changing the ratio 2 ? R/aB where R is the radius of the ring. Physically, the origin of the oscillations is the finite probability for electron and hole, created by a photon at the same point, to tunnel in the opposite directions and meet each other on the opposite side of the ring. Possible candidates for the experimental observation of the effect are recently discovered self-assembled quantum ring-like structures of InAs embedded in GaAs.^2,3 ^1R.A. Römer and M.E. Raikh, preprint cond-mat/9906314. ^2A. Lorke et al., Microelectronic Engeneering 47, 95 (1999). ^3H. Petterson et al., Proceedings of EP2DS-13, to be published in Physica E, (1999).
Spinless Aharonov-Bohm problem in curved space
Edilberto O. Silva; Sérgio C. Ulhoa; Fabiano M. Andrade; Cleverson Filgueiras; R. G. G. Amorin
2015-02-25
The dynamics of a spinless charged particle under the influence of a magnetic field in curved space is considered. We chose the surface as being a cone defined by a line element in polar coordinates. The geometry of this line element establishes that the motion of the particle can occur on the surface of a cone or an anti-cone. As a consequence of the nontrivial topology of the cone and also because of two-dimensional confinement, the geometric potential should be taken into account. At first, we establish the conditions for the particle describing a circular path in such a context. Because of the presence of the geometric potential, which contains a singular term, we use the self-adjoint extension method in order to describe the dynamics in all space including the singularity. Expressions are obtained for the bound state energies and wave functions.
Aharonov-Bohm interference in topological insulator nanoribbons
Hailin Peng; Keji Lai; Desheng Kong; Stefan Meister; Yulin Chen; Xiao-Liang Qi; Shou-Cheng Zhang; Zhi-Xun Shen; Yi Cui
2010-01-01
Topological insulators represent unusual phases of quantum matter with an insulating bulk gap and gapless edges or surface states. The two-dimensional topological insulator phase was predicted in HgTe quantum wells and confirmed by transport measurements. Recently, Bi2Se3 and related materials have been proposed as three-dimensional topological insulators with a single Dirac cone on the surface, protected by time-reversal symmetry. The
The Dynamical Mechanism of the Aharonov-Bohm Effect
R. F. Wang
2007-05-28
In this paper, it is emphasized that the dynamical cause for the A-B effect is the superimposed energy between the magnetic field produced by the moving charges and that in the solenoid, instead of the existence of the vector potential. If such a superposition between the magnetic fields can be eliminated, the A-B effect should not be observed any more. To verify this viewpoint, a new experimental method using a SQUID is suggested in this paper.
AZO DYES ARE MAJOR CONTRIBUTORS TO THE MUTAGENIC ACTIVITY DETECTED IN THE CRISTAIS RIVER WATERS
To determine if compounds from a dye processing plant were contributing to the mutagenicity repeatedly found in the Cristais River, Sao Paulo, Brazil, we chemically characterized the treated industrial effluent, raw and treated water, and the sludge produced by a Drinking Water T...
Ordem orientacional em sistemas com interaes competitivas
Stariolo, Daniel AdriÃ¡n
Ordem orientacional em sistemas com interaÃ§Ãµes competitivas Daniel A. Stariolo Universidade Federal do Rio Grande do Sul 2012 i #12;SumÃ¡rio 1 Ordem em sistemas de matÃ©ria condensada 1 1.1 Ordem posicional e orientacional em cristais lÃquidos, microemul- sÃµes e copolÃmeros de dibloco
In order to verify if dyestuffs within an effluent of a textile industry was contributing to the systematic mutagenicity detected in the Cristais River, within the metropolitan region of Sao Paulo, mutagenic samples of the industrial effluent, crude water, and treated silt of the...
Yannouleas, Constantine; Landman, Uzi
2015-01-01
The unique ultra-relativistic, massless, nature of electron states in two-dimensional extended graphene sheets, brought about by the honeycomb lattice arrangement of carbon atoms in two-dimensions, provides ingress to explorations of fundamental physical phenomena in graphene nanostructures. Here we explore the emergence of new behavior of electrons in atomically precise segmented graphene nanoribbons (GNRs) and graphene rings with the use of tight-binding calculations, non-equilibrium Green's function transport theory, and a newly developed Dirac continuum model that absorbs the valence-to-conductance energy gaps as position-dependent masses, including topological-in-origin mass-barriers at the contacts between segments. Through transport investigations in variable-width segmented GNRs with armchair, zigzag, and mixed edge terminations we uncover development of new Fabry-Perot-like interference patterns in segmented GNRs, a crossover from the ultra-relativistic massless regime, characteristic of extended gra...
Non-Abelian Aharonov-Bohm Scattering of Spin 1/2 Particles
M. Gomes; L. C. Malacarne; A. J. da Silva
2000-04-24
We study the low energy regime of the scattering of two fermionic particles carrying isospin 1/2 and interacting through a non-Abelian Chern-Simons field. We calculate the one-loop scattering amplitude for both the nonrelativistic and also for the relativistic theory. In the relativistic case we introduce an intermediate cutoff, separating the regions with low and high loop momenta integration. In this procedure purely relativistic field theory effects as the vacuum polarization and anomalous magnetic moment corrections are automatically incorporated.
Exciton storage in type-II quantum dots using the optical Aharonov-Bohm effect
Climente, Juan I.; Planelles, Josep, E-mail: josep.planelles@uji.es [Departament de Química Física i Analítica, Universitat Jaume I, E-12080 Castelló (Spain)
2014-05-12
We investigate the bright-to-dark exciton conversion efficiency in type-II quantum dots subject to a perpendicular magnetic field. To this end, we take the exciton storage protocol recently proposed by Simonin and co-workers [Phys. Rev. B 89, 075304 (2014)] and simulate its coherent dynamics. We confirm the storage is efficient in perfectly circular structures subject to weak external electric fields, where adiabatic evolution is dominant. In practice, however, the efficiency rapidly degrades with symmetry lowering. Besides, the use of excited states is likely unfeasible owing to the fast decay rates. We then propose an adaptation of the protocol which does not suffer from these limitations.
The Aharonov-Bohm effect: Mathematical Aspects of the Quantum Flow
Luis Fernando Mello; Yuri Cândido Ribeiro
2007-01-08
This paper addresses the scattering of a beam of charged particles by an infinitely long magnetic string in the context of the hydrodynamical approach to quantum mechanics. The scattering is qualitatively analyzed by two approaches. In the first approach, the quantum flow is studied via a one-parameter family of complex potentials. In the second approach, the qualitative theory of planar differential equations is used to obtain a one-parameter family of Hamiltonian functions which determine the phase portraits of the systems.
Dynamic Response of Isolated Aharonov-Bohm Rings Coupled to an Electromagnetic Resonator
NASA Astrophysics Data System (ADS)
Reulet, Bertrand; Ramin, Michel; Bouchiat, Hélène; Mailly, Dominique
1995-07-01
We have measured the flux dependence of both the real and the imaginary conductance of GaAs/GaAlAs isolated mesoscopic rings at 310 MHz. The rings are coupled to a highly sensitive electromagnetic superconducting microresonator and lead to a perturbation of the resonance frequency and quality factor. This experiment provides a new tool for the investigation of the conductance of mesoscopic systems without the need for invasive probes. The results obtained can be compared with recent theoretical predictions emphasizing the differences between isolated and connected geometries and the relation between ac conductance and persistent currents.
Chern-Simons theory of scalar particles and the Aharonov-Bohm effect
M. Boz; V. Fainberg; N. K. Pak
1995-01-01
The S-matrix of the relativistic theory of charged scalar particles interacting via the Chern-Simons field is shown to be formally equivalent to the S-matrix of scalar QED in 2 + 1 dimensions in which the Feynman diagrams with external photon lines are excluded and the propagators of the Chern-Simons particles are substituted instead of the photon propagators. It is shown
Classical light analogue of the non-local Aharonov-Bohm effect
Nandan Satapathy; Deepak Pandey; Poonam Mehta; Supurna Sinha; Joseph Samuel; Hema Ramachandran
2012-01-01
We demonstrate the existence of a non-local geometric phase in the intensity-intensity correlations of classical incoherent light, that is not seen in the lower-order correlations. This two-photon Pancharatnam phase was observed and modulated in a Mach-Zehnder interferometer. Using acousto-optic interaction, independent phase noise was introduced to light in the two arms of the interferometer to create two independent incoherent classical
Slow photons as charged quasi-particles, and photonic Aharonov-Bohm effect
Karl-Peter Marzlin; Juergen Appel; Alexander Lvovsky
2007-01-01
Recently we have proposed the method of Raman Adiabatic Transfer of Optical States (RATOS) to manipulate the optical state of light. A four-level atomic medium in double-lambda configuration is interacting with two pump fields and a signal photon with very slow group velocity. An adiabatic change in time of the pump fields can then generate a slow photon in a
The Aharonov-Bohm Effect Revisited by an Acoustic Time-Reversal Mirror
Philippe Roux; Julien de Rosny; Mickael Tanter; Mathias Fink
1997-01-01
We take advantage of the violation of time-reversal invariance for acoustic waves to achieve a new way of characterizing a vorticity field with a double time-reversal mirror (TRM). In particular, we show experimentally that the double TRM works as a vorticity amplifier. In the case of a vorticity filament, the sound-vorticity interaction is interpreted as the acoustical analog of the
Aharonov-Bohm Exciton Splittings in Carbon Nanotubes in Ultra-High Magnetic Fields
NASA Astrophysics Data System (ADS)
Takeyama, S.; Suzuki, H.; Otsubo, Y.; Yokoi, H.; Murakami, Y.; Maruyama, S.
2011-12-01
The Ajiki-Ando (A-A) splitting of single-walled carbon nanotubes was observed by the magneto-absorption measurements conducted up to a very high magnetic field, 78 T for PFO-samples. The well-resolved absorption spectra from the E11 transitions in the PFO-samples showed a clear A-A splitting. The electro-magnetic flux compression method was used for generation of the field up to 360 T, where the absorption spectra of the E22 transition of the HiPco samples were measured by the streak spectroscopy. Parameters for the A-A splitting were determined for different chiralty of each case.
Zimmermann, Roland
-radiative decay. We assume that both the electron and the hole are strongly confined in a narrow quantum well symmetry is supposed. This enables to write the exciton wave function in the envelope function formalism confinement wave functions centered at z = 0 and ua(ra) are radial confinement wave functions centered around
Carlos O. Gorrichategui III
2004-01-01
A thorough analysis is presented of the (2+1) space-time Dirac equation coupled to a confined magnetic field (B0) in both the bound-state sector and the scattering sector of the interacting theory. Contrary to earlier approaches to this problem, we start by keeping all the characteristic physical parameters arbitrary. We present and compare two nonequivalent descriptions: (i) the framework in which
Zimmermann, Roland
with interesting prop- erties such as crystallization. The approximations used origi- nally allowed for an analytic the action of the vector potential on quantum mechanical particles. The idea behind is quite simple: A charge solution of the ground state and the related persistent current. Later on, a full calculation was carried
Yeong-Lieh Lin
1995-01-01
We investigate quantum interference effects--due to electron motion on lattices immersed in a magnetic field --in a variety of condensed matter systems. These effects arise from the interference between magnetic phase factors associated with different electron paths. The spirit of our approach follows Feynman's programme: to derive physical quantities in terms of \\
Gusev, Guennady
-mode ballistic ring M. Casse´,1,2 Z. D. Kvon,3 G. M. Gusev,4 E. B. Olshanetskii,1,3 L. V. Litvin,3 A. V oscillations in a single mode ballistic ring has been measured. The experimental data is analyzed using to fab- ricate ballistic ring interferometers.2,3 At low temperatures the electron phase coherence
Boyer, Edmond
1997-01-01
at Dislocations in Lattice-Mismatched Heterostructures T. Figielski (*), T. Wosifiski and A. M~kosa Institute and other imperfections PACS.73 40.Kp III-V semiconductor-to-semiconductor contacts, p-n junctions interference of holes in macroscopic semiconductor sample containing an array of straight-line dislocations
Raymond Chiao
2011-04-22
The minimal coupling rule is "derived" starting from Landau's relativistically invariant classical action for a charge in the presence of classical electromagnetic fields. Experiments are then proposed to see the resulting electromagnetic angular momentum of a classical, "lumpy" charged ring enclosing a solenoid. These classical, macroscopic experiments are similar in spirit to those proposed by Aharonov and Bohm at the quantum level.
Kouznetsov, Dmitrii
in Annular Cylindrical Boxes E. Ley-Koo1¤, G. Villa-Torres1¤, and D. Kouznetsov2 1 Instituto de Fi´sica-UNAM., Apartado Postal 20-364, 01000 M´exico, D. F. M´exico 2 Mathematical Building, Box 87, University of Arizona an annular cylindrical box and in the presence of an axial uniform magnetic field is solved in two
Surface Science Reports 64 (2009) 191232 Contents lists available at ScienceDirect
Ihn, Thomas
2009-01-01
dots Gallium arsenide IIIV semiconductors Photonelectron interactions Quantum point contacts AharonovBohm quantum dot embedded in the AharonovBohm ring interferometer. AharonovBohm rings are traditionally used effect a b s t r a c t We use time-resolved charge detection techniques to investigate single
RAPID COMMUNICATIONS PHYSICAL REVIEW B 87, 060301(R) (2013)
Fan, Shanhui
2013-01-01
of a photonic Aharonov-Bohm effect at radio frequencies Kejie Fang,1 Zongfu Yu,2 and Shanhui Fan2 1 Department experimentally demonstrate the photonic Aharonov-Bohm effect. The effect relies on the nonreciprocal phase a gauge potential for photons, it is therefore important to observe the photonic Aharonov-Bohm effect
Non-reciprocal phase shift induced by an effective magnetic flux for light
Lipson, Michal
experimentally for electrons in the AharonovBohm experiment. Here, we replicate this exper- iment using photons) and the direction-dependent phase is equivalent to the AharonovBohm effect20 for electrons, where the electrons for radiofrequency photons was observed using a photonic AharonovBohm interferometer21 . The demonstration
Maruyama, Shigeo
Key words : Single-walled carbon nanotubes, Excitons, the Aharonov-Bohm effect. PACS 71.35.Ji, 78 degeneracy, and the amount of state splitting is determined by the Aharonov-Bohm phase. We show experimental: Coulomb- induced splitting; AB: Aharonov-Bohm-induced splitting. Both states become optically
The Electromagnetic Duality Formulation of Geometric Phases
NASA Astrophysics Data System (ADS)
Zhang, Yuchao; Li, Kang
2015-06-01
This paper focuses on the electromagnetic(EM) duality formulation of geometric phases of Aharonov-Bohm(A-B) effect and Aharonov-Casher(A-C) effect. Through the two four-vector potential formulation of electromagnetic theory, we construct a EM duality formulation for both A-B effect and A-C effect. The He-McKellar-Wilkens(HMW) effect is included as a EM duality counterpart of the A-C effect, and also the EM duality counterpart of the A-B effect is also predicted.
Can Real Forces Be Induced by Interference of Quantum Wavefunctions?
NASA Astrophysics Data System (ADS)
Kaminer, Ido; Nemirovsky, Jonathan; Rechtsman, Mikael; Bekenstein, Rivka; Segev, Mordechai
2013-04-01
In 1958, a revolutionary paper by Aharonov and Bohm predicted a phase difference between two parts of an electron wavefunction even when being confined to a regime with no EM field. The Aharonov-Bohm effect was groundbreaking: proving that the EM vector potential is a real physical quantity, affecting the outcome of experiments not only through the EM fields extracted from it. But is the EM potential a real necessity for an Aharonov-Bohm-type effect? Can it exist in a potential-free system such as free-space? Here, we find self-accelerating wavepackets that are solutions of the free Dirac equation, for massive/massless fermions/bosons. These accelerating Dirac particles mimic the dynamics of a free-charge moving under a ``virtual'' EM field, even though no field is acting and there is no charge: the entire dynamics is a direct result of the initial conditions. We show that such particles display an effective Aharonov-Bohm effect caused by exactly the same ``virtual'' potential that also ``causes'' the acceleration. Altogether, along the trajectory, there is no way to distinguish between a real force and the self-induced force - it is real by all measurable quantities. This proves that one can create all effects induced by EM fields by only controlling the initial conditions of a wave pattern, while the dynamics is in free-space. These phenomena can be observed in various settings: e.g., optical waves in honeycomb photonic lattices or in hyperbolic metamaterials, and matter waves in honeycomb interference structures.
Timothy H. Boyer
2006-01-01
The classical electromagnetic interaction of a point charge and a magnet is discussed by first calculating the interaction of a point charge with a simple model magnetic moment and then suggesting a multiparticle limit. The Darwin–Lagrangian is used to analyse the electromagnetic behaviour of the model magnetic moment (composed of two oppositely charged particles of different masses in an initially
Chords: Em 022000 Em Em Em Em C C C C
Reiners, Peter W.
Verse 1 Chorus Verse 2 Chorus Verse 3 Chords: Em 022000 C 035553 G 320002 F 133211 Intro: Em Em Em Em C C C C Em Em Em Em C C C C Em Em Em Em C C C C Em Em Em Em C C C C Verse: Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C C C G G G G G G G G Em Em Em Em C C
J. Phys. II trance 4 (1994) 1999-2027 NOVEMBER 1994, PAGE 1999 Classification
Paris-Sud XI, Université de
1994-01-01
experiments of Kasevich and Chu, and the atomic equivalents of the Sagnac and Aharonov-Bohm effects and Chu), a particle in a rotating frame, and the atomic equivalents of the Aharonov-Bohm effects. 1. Path in the more traditional types of interferometry using photons, electrons and neutrons. The development
Physica B 249--251 (1998) 295--301 Dephasing due to which path detector
Buks, Eyal
1998-01-01
rights reserved. Keywords: Dephasing; Quantum dots; Aharonov--Bohm effect Bohr's complementarity temperature techniques allow observation of a variety of coherent effects, such as Aharonov--Bohm (AB demonstrated recently using parametric down conversion of photons where one photon had been used to deter- mine
Scattering theory of electrical Markus Bttiker
Paris-Sud 11, Université de
-particle Aharonov-Bohm effect Entanglement Noise Dynamic conductance Quantum pumping 4 #12;Conductance from;Aharonov-Bohm conductance oscillations 14 Gefen, Imry, Azbel, PRL 2004 Buttiker, Imry, Azbel, Phys. Rev. A to Mesoscopic Physics, Y. Imry, Oxford University Press, 1997. Mesoscopic Physics of Electrons and Photons E
Magnetic Brightening of Carbon Nanotube Photoluminescence through Symmetry Breaking
Maruyama, Shigeo
- dependent exciton band structure and the interplay of Coulomb interactions and the Aharonov- Bohm effect is shown to be a consequence of broken time reversal symmetry, working in tandem with the Aharonov-Bohm effect, and has far-reaching implications for the importance of symmetry manipulation as a possible means
T h e o p e n a c c e s s j o u r n a l f o r p h y s i c s New Journal of Physics
Ihn, Thomas
. After having been observed in metallic nanostructures [5, 6], the AharonovBohm effect was studied. In semiconductor nanostructures, quantum interference of electron waves is found very prominently in the AharonovBohm [1] and the Fano [2] effects. In contrast to photons in vacuum, which do not interact with each other
Photonic de Haas-van Alphen effect Kejie Fang, Zongfu Yu, and Shanhui Fan
Fan, Shanhui
waveguide array," Phys. Rev. Lett. 103, 033902 (2009). 9. K. Fang, Z. Yu, and S. Fan, "Photonic Aharonov-Bohm Aharonov-Bohm effect at radio frequen- cies," Phys. Rev. B 87, 060301(R) (2013). 12. Z. Yu and S. FanPhotonic de Haas-van Alphen effect Kejie Fang, Zongfu Yu, and Shanhui Fan Ginzton Laboratory
Nonlocal Geometric Phase Measurements in Polarized Interferometry with Pairs of single Photons
Paris-Sud XI, Université de
Aharonov-Bohm effect was discussed theoretically by Büttiker [10] who noted in the context of electronic phase. This effect can be used for manipulating and controlling photonic entanglement. PACS numbers: 03 correlations and is a genuinely nonlocal and multiparticle Aharonov-Bohm ef- fect [11]. This has been
Magnetic Brightening of Carbon Nanotube Photoluminescence through
Kono, Junichiro
and the interplay of Coulomb interactions and the Aharonov-Bohm effect. This conclusively explains our data to be a consequence of broken time reversal symmetry, working in tandem with the Aharonov-Bohm effect, and has far- conducting SWNTs, in particular, have attracted much recent attention for photonic applications.7 They have
Momentum of electromagnetic fields, speed of light in moving media, and the photon mass
Gianfranco Spavieri; George T. Gillies
2010-05-21
In both the equations for matter and light wave propagation, the momentum of the electromagnetic fields Pe reflects the relevant em interaction. As a review of some applications of wave propagation properties, an optical experiment which tests the speed of light in moving rarefied gases is described. Moreover, Pe is also the link to the unitary vision of the quantum effects of the Aharonov-Bohm (AB) type, which provide a useful quantum approach for the limit of the photon mass mph. A bench-top experiment based on effects of the AB type that exploit new interferometric techniques, is foreseen to yield the limit mph = 10^-54 g, a value that improves upon the results achieved with other approaches.
Momentum of electromagnetic fields, speed of light in moving media, and the photon mass
Spavieri, Gianfranco
2010-01-01
In both the equations for matter and light wave propagation, the momentum of the electromagnetic fields Pe reflects the relevant em interaction. As a review of some applications of wave propagation properties, an optical experiment which tests the speed of light in moving rarefied gases is described. Moreover, Pe is also the link to the unitary vision of the quantum effects of the Aharonov-Bohm (AB) type, which provide a useful quantum approach for the limit of the photon mass mph. A bench-top experiment based on effects of the AB type that exploit new interferometric techniques, is foreseen to yield the limit mph = 10^-54 g, a value that improves upon the results achieved with other approaches.
J Low Temp Phys DOI 10.1007/s10909-009-0112-8
Natelson, Douglas
caused by the alignment-- e.g. the shift of optical transitions due to the Aharonov-Bohm effect) where denotes the radiation photon energy and (av) indicates the spectral average. The same integration
Two Further Experiments on Electron Interference
ERIC Educational Resources Information Center
Matteucci, G.; Pozzi, G.
1978-01-01
Presents the results of two experiments concerning the phenomena of the interference of probabilities and of the so called Aharonov-Bohm effect. An electron biprism and a standard electron microscope have been used for the experiments. (Author/GA)
Fluctuating electromagnetic fields and electron coherence
Jen-Tsung Hsiang
2004-01-01
It is well-known that a charged particle in a constant magnetic field background will acquire a phase, the Aharonov-Bohm phase, which depends on the path it travels and on the strength of the background field. This effect has long been recognized and experimentally verified. However, the effect of a fluctuating Aharonov-Bohm phase was first discussed in the works of Stern,
Johann Ambrosius Barth; Hans De Raedt; Kristel Michielsen
We present the results of a computer simulation study of charged-particle interferometry, combining features of both the Aharonov-Bohm and Hanbury Brown-Twiss experiment. In contrast to a previous theoretical analysis of this experiment, we find that the Aharonov-Bohm effect is also pre- sent in the cross-correlated two-particle intensity. A simple, time-independent scattering theory that leads to conclusions that are in concert
Phase measurement of photon-assisted tunneling through a quantum dot
A. P. Jauho
1997-01-01
Recent double-slit interference experiments have demonstrated the possibility\\u000aof probing the phase of the complex transmission coefficient of a quantum dot\\u000avia the Aharonov-Bohm effect. We propose an extension of these experiments: an\\u000aac voltage imposed on the side gate with the concomitant photonic sidebands\\u000aleads to additional structure both in the amplitude and in the phase of the\\u000aAharonov-Bohm
Quantum interference in an electron-hole graphene ring system
NASA Astrophysics Data System (ADS)
Smirnov, D.; Schmidt, H.; Haug, R. J.
2013-12-01
Quantum interference is observed in a graphene ring system via the Aharonov Bohm effect. As graphene is a gapless semiconductor, this geometry allows to study the unique situation of quantum interference between electrons and holes in addition to the unipolar quantum interference. The period and amplitude of the observed Aharonov-Bohm oscillations are independent of the sign of the applied gate voltage showing the equivalence between unipolar and dipolar interference.
Electromagnetic momentum in frontiers of modern physics
NASA Astrophysics Data System (ADS)
Spavieri, Gianfranco; Erazo, Jesús; Sanchez, Arturo; Aguirre, Felix; Gillies, George T.; Rodriguez, Miguel
2008-09-01
We review the role of the momentum of the electromagnetic (EM) fields P e in several areas of modern physics. P e represents the EM interaction in equations for matter and light waves propagation. As an application of wave propagation properties, a first order optical experiment which tests the speed of light in moving rarefied gases is presented. Within a classical context, the momentum P e appears also in proposed tests of EM interactions involving open currents and angular momentum conservation laws. Moreover, P e is the link to the unitary vision of the quantum effects of the Aharonov-Bohm (AB) type and, for several of these effects, the strength of P e is evaluated. These effects provide a quantum approach to evaluate the limit of the photon mass m ph. A new effect of the AB type, together with the scalar AB effect, provides the basis for table-top experiments which yield the limit m ph = 9.4 × 10-52g, a value that improves the results achieved with recent classical and quantum approaches.
Instituto de Sistemas e Robotica
Estudantes em campanha pela qualidade #12;Alunos unidos pela educação Ensino. No dia em que se ensino superior. Promulgado pela Assembleia da República em 1987, o Dia Nacional do Estudante comemora, aquando da crise académica vivida em Portugal. Agora, as associações académicas aproveitam o dia para
Instituto de Sistemas e Robotica
LISBOA Novo mestrado em Engenharia Petrolífera > A secretária de Estado da Ciência, Leonor Parreira, inaugu- ra hoje, em Lisboa, um novo mes- trado em Engenharia do Petróleo patrocinado pela Galp e Coimbra, a Universidade de Aveiro e a Universidade do Minho. O mestrado, em que serão abor- dadas áreas
Theory of phase-sensitive measurement of photon-assisted tunneling through a quantum dot
NASA Astrophysics Data System (ADS)
Jauho, A. P.; Wingreen, Ned S.
1998-10-01
Recent double-slit interference experiments [Schuster et al., Nature (London) 385, 417 (1997)] have demonstrated the possibility of probing the phase of the complex transmission coefficient of a quantum dot via the Aharonov-Bohm effect. We propose an extension of these experiments: an ac voltage imposed on the side gate with the concomitant photonic sidebands leads to additional structure both in the amplitude and in the phase of the Aharonov-Bohm signal. Observation of these effects would be a definitive proof of coherent absorption and reemission of photons from the ac source.
Aharonov-Casher effect in massive-photon electrodynamics
NASA Astrophysics Data System (ADS)
Fuchs, Christopher
1990-10-01
In concurrence with a recent calculation for the Aharonov-Bohm effect by Boulware and Deser, it is shown that the Aharonov-Casher phase shift for a neutral magnetic dipole diffracted around a uniform infinitely long line charge still occurs in massive-photon electrodynamics. This effect reduces smoothly to the original in the limit that the photon mass vanishes. Unlike the case for the Aharonov-Bohm effect, however, the neutral particle has no classical acceleration regardless of the photon mass. This demonstrates the existence of pure nonlocal effects for nongauge fields.
Exciton splitting in semiconducting carbon nanotubes in ultrahigh magnetic fields above 300 T
NASA Astrophysics Data System (ADS)
Nakamura, Daisuke; Sasaki, Tatsuya; Zhou, Weihang; Liu, Huaping; Kataura, Hiromichi; Takeyama, Shojiro
2015-06-01
In high magnetic fields, the exciton absorption spectrum of a semiconducting single-walled carbon nanotube splits as a result of Aharonov-Bohm magnetic flux. A magnetic field of 370 T, generated by the electromagnetic flux compression destructive pulsed magnet-coil technique, was applied to single-chirality semiconducting carbon nanotubes. Using streak spectroscopy, we demonstrated the separation of the independent band-edge exciton states at the K and K' points of the Brillouin zone after the mixing of the dark and bright states above 150 T. These results enable a quantitative discussion of the whole picture of the Aharonov-Bohm effect in single-walled carbon nanotubes.
Charge-fluctuation-induced dephasing in a gated mesoscopic interferometer
NASA Astrophysics Data System (ADS)
Seelig, Georg; Büttiker, Markus
2001-12-01
The reduction of the amplitude of Aharonov-Bohm oscillations in a ballistic one-channel mesoscopic interferometer due to charge fluctuations is investigated. In the arrangement considered the interferometer has four terminals and is coupled to macroscopic metallic side gates. The Aharonov-Bohm oscillation amplitude is calculated as a function of temperature and the strength of coupling between the ring and the side gates. The resulting dephasing rate is linear in temperature in agreement with recent experiments. Our derivation emphasizes the relationship between dephasing, ac-transport, and charge fluctuations.
Chapman, Michael S.
Leica EM UC7 Leica EM FC7 High Quality Ultramicrotome for Precise Room Temperature and Cryo its latest specimen preparation technology: the Leica EM UC7 ultramicrotome and the Leica EM FC7 cryo chamber attachment. #12;3 Leica EM UC7 The Leica EM UC7 prepares excellent quality semi- and ultra
Brookhaven EM Completion Project Environmental
Homes, Christopher C.
Brookhaven EM Completion Project Office of Environmental Management 1 American Recovery Site Office Brookhaven National Laboratory Community Advisory Council April 15, 2009 #12;Brookhaven EM Environmental Management (EM) Funding and Goals Brookhaven EM ARRA Projects Description of ARRA Projects #12
Not Available
1993-07-01
It is the intent of EM International to describe the Office of Environmental Restoration and Waste Management`s (EM`s) various roles and responsibilities within the international community. Cooperative agreements and programs, descriptions of projects and technologies, and synopses of visits to international sites are all highlighted in this semiannual journal. Focus on EM programs in this issue is on international collaboration in vitrification projects. Technology highlights covers: in situ sealing for contaminated sites; and remote sensors for toxic pollutants. Section on profiles of countries includes: Arctic contamination by the former Soviet Union, and EM activities with Germany--cooperative arrangements.
of dipolar excitons within a one-dimensional channel" Physical Review Letters. 2009; 103: 126402-1 - 126402 in submicron InGaAs wires". Physical Review Letters. 2006; 97: 036805-1 - 036805-4. 4. Holleitner AW, Blick RH dots embedded in an Aharonov-Bohm interferometer". Physical Review Letters. 2001; 87: 256802-1 - 256802
Is it possible the ab ini&o thermodynamics with defects?
Cambridge, University of
. 51. #12;Geometric theory of defects ElasTc deformaTon (Euclidean) Levi-Civita connec that the metric becomes nontrivial in this coordinate system. Riemann-Cartan manifold theory., Phys. Rev. LeC. 80, 2257 (1998) #12;Aharonov-Bohm effect of the spin wave by a screw
Quantum Phenomena Observed Using Electrons
Tonomura, Akira [Okinawa Institute of Science and Technology, Onna-son, Okinawa 904-0412 (Japan); Advanced Research Laboratory, Hitachi, Ltd., Hatoyama, Saitama, 350-0395 (Japan); Advanced Science Institute, RIKEN, Wako, Saitama, 351-0198 (Japan)
2011-05-06
Electron phase microscopy based on the Aharonov-Bohm (AB) effect principle has been used to illuminate fundamental phenomena concerning magnetism and superconductivity by visualizing quantitative magnetic lines of force. This paper deals with confirmation experiments on the AB effect, the magnetization process of tiny magnetic heads for perpendicular recording, and vortex behaviors in high-Tc superconductors.
Quantum Paradoxes: Quantum Theory for the Perplexed
Yakir Aharonov; Daniel Rohrlich
2003-01-01
A Guide through the Mysteries of Quantum Physics! Yakir Aharonov is one of the pioneers in measuring theory, the nature of quantum correlations, superselection rules, and geometric phases and has been awarded numerous scientific honors. The author has contributed monumental concepts to theoretical physics, especially the Aharonov-Bohm effect and the Aharonov-Casher effect. Together with Daniel Rohrlich of the Weizmann Institute,
Coherent properties of in plane gated submicron rings in a small-signal regime
Gusev, Guennady
) and the microwave EMF dVEMF/dVG were measured in magnetic ®elds up to 2 T at temperatures T 4.2 K. It was shown rights reserved. Keywords: Electron interferometer; Aharonov±Bohm eect; Heterojunction 1. Introduction Coherent properties of a ring solid state analog to the optical Mach±Zender interferometer ± a so called
d'Ordre: D.U. 2069 UNIVERSITE BLAISE PASCAL
Boyer, Edmond
of exciton-polaritons 83 4.1 Aharonov-Bohm phase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84 . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 1.3 Strongly coupled excitons and photons: polaritons . . . . . . . . . . . . . . 19 1.3.1 Bulk,version1-13Oct2011 #12;4 CONTENTS 3 Josephson effect of excitons and exciton-polaritons 65 3
Optical analogue for phase-sensitive measurements in quantum-transport experiments
D. S. Citrin
1999-01-01
The Aharonov-Bohm effect has recently been employed to measure the quantum-mechanical phase of an electron propagating ballistically through a quantum dot (QD) contained in one arm of the interferometer [Schuster et al., Nature (London) 385, 417 (1997)]. Jauho and Wingreen [Phys. Rev. B 58, 9619 (1998)] have analyzed this geometry under conditions where the QD is modulated harmonically in time
Zheludev, Nikolay
2014-01-01
observation of the time-dependent Aharonov-Bohm effect [9,12]. Due to complexity of the current distribution Centre & Centre for Photonic Metamaterials, University of Southampton, Southampton SO17 1BJ, United Kingdom 2 Centre for Disruptive Photonic Technologies, Nanyang Technological University, Singapore 637371
Journal of Electron Spectroscopy and Related Phenomena 109 (2000) 3349 www.elsevier.nl/locate/elspec
Brune, Harald
2000-01-01
influence the phase coherence [1]. On the other hand, length scale [1]. Examples include AharonovBohm L with high-resolution angle-resolved photoemission and fem- tosecond two-photon photoemission measurements is reduced by inelastic scattering processes likef oscillations, quantum Hall effect, Friedel oscillations
Towards a Gyroscope with a Large Interferometer Area, Testing the Fundamentals of Physics
Franck Michaud; Thomas Leveque; Arnaud Landragin
2009-01-01
After having investigate the limits of our previous inertial sensor using a cold atom interferometer of caesuim in the all six axis of inertia [1], we project to built a brand new second and better version of interferometer, in order to improve the high accuracy and to be able to do some testing of fundamental physics (atomic neutrality, Aharonov-Bohm effect,
Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation
Altschul, B
2007-01-01
If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10^{-32} e level.
Nabben, Reinhard
annealing process J. Appl. Phys. 111, 104304 (2012) Spin accumulation in a multi-arm Aharonov-Bohm. Phys. Lett. 100, 241109 (2012) Refrigeration effect in a single-level quantum dot with thermal bias diodes and laser diodes,1 and in quantum information processing, like high-temperature single-photon
Optics and interferometry with atoms and molecules Alexander D. Cronin*
Cronin, Alex D.
. Aharonov-Bohm and Aharonov-Casher effects 1089 3. Berry phase 1090 4. effect 1063 E. Time-dependent diffraction 1064 1. Vibrating mirrors 1064 2. Oscillating potentials 1065 3 in Talbot-Lau interferometer 1084 c. Photon scattering in an interferometer 1084 d. Scattering from
VistasinAstronomy,Vol.37,pp.253-256,1993 PrintedinGreatBritain.Allrightsreserved.
Vaidman, Lev
the region. Quantum mechanics allows inferring the existence of an object in a nonlocal way via Aharonov-Bohm effect even when the object creates no electromagnetic field outside a certain space region, but only of single photon states. Thus we propose to use the Mach-Zehnder interferometer with such a source of single
Giraud, Olivier
though the two-particle Aharonov-Bohm effect 7 demonstrated in a re- cent experiment 13 suggests on the correlations of measurement outcomes of spatially sepa- rated observers. Experiments with entangled photons are easier to keep track of than photons. Progress was recently achieved in this direction in an experiment
Atomic spectroscopy and the photon mass: effects on the 21 cm radiation Adam Caccavano*
Leung, Pui-Tak "Peter"
1 Atomic spectroscopy and the photon mass: effects on the 21 cm radiation Adam Caccavano* and P. T. Abstract The effects due to a finite photon mass on atomic spectroscopy are explored, for the purpose of electromagnetic waves in vacuum. In the quantum case, interference phenomena based on the Aharonov-Bohm type
The Interactions and Excitations of Gauge Vortices
Mark Gower Alford
1990-01-01
Gauge vortices, for example cosmic strings, are topological solitons produced in the spontaneous breakdown of gauge symmetries, and possess long range pure gauge fields associated with the broken symmetries. This thesis explores the interactions of matter with the gauge field of a vortex, and the low energy excitations (zero modes) of the vortex. The interactions occur via the Aharonov -Bohm
Remarks on Aharanov-Bohm effect and geometric phase
S C Tiwari
2004-01-01
Recently the physical mechanism for geometric phase in optics has been elucidated in terms of the angular momentum holonomy proposed in 1992. Aharonov and Kaufherr (PRL, 92, 070404, 2004) revisit the Aharonov-Bohm effect, and propose non-local exchange of a conserved, gauge invariant quantity that changes the modular momentum of the particle that is responsible for the AB phase shift. We
Non-local geometric phase in two-photon interferometry , O. Alibart1
Paris-Sud XI, Université de
of entanglement between spatially separated quantum channels or systems. A mul- tiparticle Aharonov-Bohm effect traced out by a pair of single photons. Local measurements at either detector do not reveal the effect nonlocal effect. We show experimentally that coincidence rates of photon arrival times at separated
ccsd-00001177,version2-1Feb2005 Loss of quantum coherence in a system coupled to a zero-temperature
Paris-Sud XI, Université de
, we propose the sketch of an AharonovBohm-like interferometer show- ing, through interference, even in the zero temperature limit. 1 Introduction The effects of the interaction between a quantum electrons, phonons, photons, or scatterers. Which environ- ment dominates the destruction of interference
Nori, Franco
2014-01-01
an unconventional quantum Hall effect [1]; the possibility of testing the Klein paradox [2]; the Aharonov-Bohm-magnetic-polarized waves localized on graphene in photonic crystals Yu. O. Averkov* and V. M. Yakovenko A.Ya. Usikov in the same frequency range along a graphene layer inserted in a photonic crystal. In addition, we studied
Manifestions of Berry's topological phase for the photon
R. Y. Chiao; Y.-S. Wu
1986-01-01
Recently, Berry (1984) recognized in quantum mechanics a topological phase factor arising from the adiabatic transport of a system around a closed circuit, which is essentially the Aharonov-Bohm effect in parameter space. Here manifestations of this phase factor are considered for a photon in a state of adiabatically invariant helicity. An interferometer is suggested to see this phase. Also, an
Paris-Sud XI, Université de
symmetry. Currently, quantum ring (QR) structures are of great interest for the optical Aharonov-Bohm (AB University, Gyeonggi-do 430-714, South Korea and 5 Nano-Photonics Research Center, KIST, Seoul, 136) effect [1 5]. While the rotating charge in the shell of a type-II quantum dot (QD) determines the AB
Quantum mechanical effects of topological origin
NASA Astrophysics Data System (ADS)
Duru, I. H.
1993-03-01
Following a brief review of the original Casimir and Aharonov-Bohm effects, some other effects of similar natures are mentioned. A Casimir interaction between AB fluxes is presented. Possible realizations of the Casimir effects for massive charged fields in solid state structures and a new AB effect for photons are suggested.
New quantum effect of confined magnetic flux on electrons
NASA Astrophysics Data System (ADS)
Silverman, M. P.
1986-10-01
A charged particle analogue of the Hanbury Brown-Twiss experiments with photons is described wherein the correlation of electron intensity at two detectors is modulated by magnetic flux confined to a region from which the electrons are excluded. The experimental conditions differ substantially from those of the Aharonov-Bohm effect.
nature physics | VOL 6 | MARCH 2010 | www.nature.com/naturephysics 157 research highlights
Loss, Daniel
Aharonov and David Bohm proposed that a charged particle in a region of zero electric and zero magnetic things around and, envisaging a cosmic string as an oscillating solenoid in a vacuum, show that AharonovBohm gravitational effect that causes the radiation of all types of particle, including photons, and the authors show
Quantum mechanical effects of topological origin
I. H. Duru
1993-01-01
Following a brief review of the original Casimir and Aharonov-Bohm effects, some other effects of similar natures are mentioned. A Casimir interaction between AB fluxes is presented. Possible realizations of the Casimir effects for massive charged fields in solid state structures and a new AB effect for photons are suggested.
Single-Walle 4. Single-Walled Carbon Nanotubes
Kono, Junichiro
nonintuitive quantum phenomena when placed in a paral- lel magnetic field, due to the AharonovBohm effect. A number of research groups have found exotic many-body effects through a variety of transport, optical. Semiconducting nanotubes are particularly promising for photonic device applica- tions with their diameter
Kono, Junichiro
properties via the Aharonov-Bohm phase [3]. Furthermore, high-order harmonic generation is ex- pected observed previously, is resonantly enhanced whenever the pump photon energy coincides with an absorption of the Burstein-Moss effect. DOI: 10.1103/PhysRevLett.92.117402 PACS numbers: 78.47.+p, 73.22.f, 78.67.Ch Optical
Electromagnetically-Induced Transparency with Classical and Nonclassical Light
Lvovsky, Alexander
) to a constant magnetic field and (iii) the Aharonov-Bohm effect [3]. 3. Quantum tomography of slow light EIT with multiple excited levels. © 2007 Optical Society of America OCIS codes: (270.1670) Coherent optical effects the ground (5S $a $a 1/2) and the excited (5P1/2) levels are split into hyperfine sublevels. 2. Slow photon
Theory of phase-sensitive measurement of photon-assisted tunneling through a quantum dot
A. P. Jauho; Ned S. Wingreen
1998-01-01
Recent double-slit interference experiments [Schuster et al., Nature (London) 385, 417 (1997)] have demonstrated the possibility of probing the phase of the complex transmission coefficient of a quantum dot via the Aharonov-Bohm effect. We propose an extension of these experiments: an ac voltage imposed on the side gate with the concomitant photonic sidebands leads to additional structure both in the
NEST Scientific Report 2007-2009 SAW-driven electron dynamics in nanostructures
Abbondandolo, Alberto
-repetition-rate single-photon source [4] and a solid-state Hadamard gate based on a three-terminal Aharonov-Bohm ring acoustoelectric effect is the manifestation of the transport of charge carriers in a piezoelectric semiconductor) devices, this effect gives rise to acoustoelectric current quantization [3]: control over the 1D
New quantum effect of confined magnetic flux on electrons
M. P. Silverman
1986-01-01
A charged particle analogue of the Hanbury Brown-Twiss experiments with photons is described wherein the correlation of electron intensity at two detectors is modulated by magnetic flux confined to a region from which the electrons are excluded. The experimental conditions differ substantially from those of the Aharonov-Bohm effect. Permanent address: Department of Physics, Trinity College, Hartford, CT 06106, USA.
Suppression of decoherence in a graphene monolayer ring
Smirnov, D., E-mail: smirnov@nano.uni-hannover.de; Rode, J. C.; Haug, R. J. [Institut für Festkörperphysik, Leibniz Universität Hannover, Appelstr. 2, 30167 Hannover (Germany)
2014-08-25
The influence of high magnetic fields on coherent transport is investigated. A monolayer graphene quantum ring is fabricated and the Aharonov-Bohm effect is observed. For increased magnitude of the magnetic field, higher harmonics appear. This phenomenon is attributed to an increase of the phase coherence length due to reduction of spin flip scattering.
Magnetic fields and fluxes probed by coherent low-energy electron beams
Alain Degiovanni; Jacques Bardon; Vincent Georges; Roger Morin
2004-01-01
The magnetization of a nanometer size Ni needle is observed using the coherent electron beam originating from an electron point source. This at one and the same time displays the local (Lorentz force) and the nonlocal (Aharonov-Bohm phase shift) magnetic effects. The experiments are performed at three orders of magnitude lower electron energy than previous nonlocal effects observations. These experiments
Energy levels and far-infrared spectra of oval-shaped nanorings
Gutiérrez, W.; García, L. F.; Mikhailov, I. D. [Escuela de Física, Universidad Industrial de Santander, A. A. 678, Bucaramanga (Colombia)
2014-05-15
The evolution of the Aharonov-Bohm oscillation of low-lying states and far infrared spectrum associated to variation of the path curvature for electron motion along nanorings with centerlines in a form of a set of Cassini ovals, whose shape is changed continuously from a single elongated loop to two separated loops is theoretically investigated.
Escenario EM Modelo Matematico
MajÃ³s, Antonio BadÃa
j - 2012 CAB Escenario EM Modelo MatemÂ´atico Problemas FÂ´isicos Title Page 1 of 22 Back Full Screen.C.M.A.ÂC.S.I.C., Universidad de Zaragoza, ESPA~NA #12;j - 2012 CAB Escenario EM Modelo MatemÂ´atico Problemas FÂ´isicos Title negativa ? DifusiÂ´on magnÂ´etica hacia el EC #12;j - 2012 CAB Escenario EM Modelo MatemÂ´atico Problemas F
Deterministic annealing EM algorithm
Naonori Ueda; Ryohei Nakano
1998-01-01
Abstract This paper presents a deterministic annealing EM (DAEM) algorithm for maximum,likelihood estimation problems,to overcome,a local maxima problem associated with the conventional EM algorithm. In our approach, a new posterior parameterized by ‘temperature’ is derived by using the principle of maximum entropy and is used for controlling the annealing process. In the DAEM algorithm, the EM process is reformulated as
MESTRADO EM TEOLOGIA Edital 2015
MESTRADO EM TEOLOGIA Edital 2015 Este edital se destina especificamente a candidatos ao Mestrado em Teologia, com inÃcio em marÃ§o de 2015. 1. Objetivo O Programa de Mestrado em Teologia visa o eclesiÃ¡sticos. 2. DuraÃ§Ã£o: 24 meses, iniciando-se em marÃ§o de 2015 e concluindo-se em fevereiro de 2017. 3
Equipment management system (EMS)
T. Yurtsever; M. Comerford
1995-01-01
Equipment Management System (EMS) is a software tool used to monitor and track equipment states, restrictions and PM schedules in real time. EMS has been designed and customized to support the MOS-2 die production facility. The system provides graphical representation of the entire factory. Color coded icons represent equipment's current state (i.e. qualification, production, unscheduled maintenance, etc.). Preventative maintenance schedules
Environmental Media Services (EMS)
NSDL National Science Digital Library
Environmental Media Services (EMS) is a nonprofit communications clearinghouse committed to the expansion of media coverage on critical environmental and public health issues. True to their mission, EMS staff "build relationships with top scientists, physicians, and other experts to bring journalists the latest and most credible information." EMS's modest homepage is free of clutter but full of content. While several sections are under construction and updates (currently) appear irregular, a series of available articles provides useful summaries of important environmental news issues over the past six months. Current articles include "The impacts of global warming on the oceans" and "Cool companies," among others.
Psiquiatria baseada em evidências
Maurício S de Lima; Bernardo GO Soares; Josué Bacaltchuk
2000-01-01
Abstract Keywords Em psiquiatria, observa-se grande variabilidade de práticas clínicas, muitas vezes desnecessária. Essas varia- ções podem,estar relacionadas à ausência de evidência científica confiável ou ao desconhecimento,das evidên- cias de boa qualidade disponíveis. A medicina baseada em evidências (MBE) é uma combinação de estratégias que busca assegurar que o cuidado individual do paciente seja baseado na melhor informação disponível, a
PROFESSOR DO SEPT MINISTRA CONFERNCIA EM ABERTURA EM CONGRESSO E SIMPSIO EM CARUARU
ParanÃ¡, Universidade Federal do
PROFESSOR DO SEPT MINISTRA CONFERÃ?NCIA EM ABERTURA EM CONGRESSO E SIMPÃ?SIO EM CARUARU Christian Mendez Alcantara, Professor dos Cursos de GestÃ£o PÃºblica e Agente ComunitÃ¡rio em SaÃºde do Setor de ministrarÃ¡ conferÃªncia de abertura no evento: "GestÃ£o e GovernanÃ§a em SaÃºde PÃºblica: AvanÃ§os e Desafios" da
ESPECIAO ESPONTNEA EM POPULAES ESPACIALMENTE
de Aguiar, Marcus A. M.
ESPECIAÃ?Ã?O ESPONTÃ?NEA EM POPULAÃ?Ã?ES ESPACIALMENTE DISTRIBUÃDAS E PADRÃ?ES DE DIVERSIDADE Elizabeth M pÃºblico em geral. Em 1859 Charles Darwin deu passo fundamental para a soluÃ§Ã£o desse problema com a dinÃ¢mica da enorme diversidade biolÃ³gica existente em nosso planeta. Neste trabalho, discutimos um novo
Instituto de Sistemas e Robotica
Ciência feita em Portugal com mais impacto artigos As citações internacionais de artigos científicos produzidos em Portugal tiveram um "notório crescimento" nos últimos 23 anos, entre 1990 e 2012 das instituições nacionais tem progressivamente ganhado relevância. Um dado que surge numa altura em
NASA Astrophysics Data System (ADS)
Jones, K. B., II; Saxton, P. T.
2013-12-01
Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After the 1989 Loma Prieta Earthquake, American earthquake investigators predetermined magnetometer use and a minimum earthquake magnitude necessary for EM detection. This action was set in motion, due to the extensive damage incurred and public outrage concerning earthquake forecasting; however, the magnetometers employed, grounded or buried, are completely subject to static and electric fields and have yet to correlate to an identifiable precursor. Secondly, there is neither a networked array for finding any epicentral locations, nor have there been any attempts to find even one. This methodology needs dismissal, because it is overly complicated, subject to continuous change, and provides no response time. As for the minimum magnitude threshold, which was set at M5, this is simply higher than what modern technological advances have gained. Detection can now be achieved at approximately M1, which greatly improves forecasting chances. A propagating precursor has now been detected in both the field and laboratory. Field antenna testing conducted outside the NE Texas town of Timpson in February, 2013, detected three strong EM sources along with numerous weaker signals. The antenna had mobility, and observations were noted for recurrence, duration, and frequency response. Next, two directional techniques were employed, resulting in three mapped, potential epicenters. The remaining, weaker signals presented similar directionality results to more epicentral locations. In addition, the directional results of the Timpson field tests lead to the design and construction of a third prototype antenna. In a laboratory setting, experiments were created to fail igneous rock types within a custom-designed Faraday Cage. An antenna emplaced within the cage detected EM emissions, which were both reproducible and distinct, and the laboratory results paralleled field results. With a viable system and continuous monitoring, a fracture cycle could be established and observed in real-time. Sequentially, field data would be reviewed quickly for assessment; thus, leading to a much improved earthquake forecasting capability. The EM precursor determined by this method may surpass all prior precursor claims, and the general public will finally receive long overdue forecasting.
'arts martiaux! Remarques ACTIVITÉ CODE LUDIK NIVEAU HORAIRE LOCAL DURÉE EM M NM EM M NM EM M NM EM M NM EM M NM EM M NM Club d'Aïkido 02 020 0101 Débutant Lu 17h à 18h25 (cours) et Ve 18h30 à 20h25 (pratique ACTIVITÉ CODE LUDIK NIVEAU HORAIRE LOCAL DURÉE EM M NM EM M NM EM M NM EM M NM EM M NM EM M NM Club de
Emergency Medicine Resident Involvement in EMS
Adam M. Ray; David P. Sole
2007-01-01
Emergency Medical Services (EMS) activities are a required component of Emergency Medicine (EM) residency training. To determine resident involvement with EMS, all 135 Accreditation Council for Graduate Medical Education-accredited and 34 American Osteopathic Association-accredited EM residencies were surveyed in June 2005 regarding the EMS activities required of their residents. One hundred twelve surveys were completed (66% response rate). Observing with
PRODUÇÃO SUSTENTÁVEL EM RESERVAS EXTRATIVISTAS
Jose Otavio Valiante; Osmar Siena
2008-01-01
Este trabalho discute questões relacionadas à produção sustentável em Reservas Extrativistas (RESEX). Com a finalidade de identificar temas prioritários foi aplicada a ferramenta Brainwriting 6-3-5, tendo como pano de fundo a Reserva Extrativista do Rio Ouro Preto\\/RO, com uma equipe de técnicos do IBAMA em Guajará-Mirim\\/RO e representantes da comunidade da RESEX. Em um segundo momento foi aplicado um questionário
DOUTORADO EM TEOLOGIA Edital 2014/02
DOUTORADO EM TEOLOGIA Edital 2014/02 Este edital se destina especificamente a candidatos ao Doutorado em Teologia, com inÃcio em agosto de 2014. 1. Objetivo: O Programa de Doutorado em Teologia visa o eclesiÃ¡sticos. 2. DuraÃ§Ã£o: 48 meses, com inÃcio em agosto de 2014 e tÃ©rmino em julho de 2018. 3. Ãreas de
Identified EM Earthquake Precursors
NASA Astrophysics Data System (ADS)
Jones, Kenneth, II; Saxton, Patrick
2014-05-01
Many attempts have been made to determine a sound forecasting method regarding earthquakes and warn the public in turn. Presently, the animal kingdom leads the precursor list alluding to a transmission related source. By applying the animal-based model to an electromagnetic (EM) wave model, various hypotheses were formed, but the most interesting one required the use of a magnetometer with a differing design and geometry. To date, numerous, high-end magnetometers have been in use in close proximity to fault zones for potential earthquake forecasting; however, something is still amiss. The problem still resides with what exactly is forecastable and the investigating direction of EM. After a number of custom rock experiments, two hypotheses were formed which could answer the EM wave model. The first hypothesis concerned a sufficient and continuous electron movement either by surface or penetrative flow, and the second regarded a novel approach to radio transmission. Electron flow along fracture surfaces was determined to be inadequate in creating strong EM fields, because rock has a very high electrical resistance making it a high quality insulator. Penetrative flow could not be corroborated as well, because it was discovered that rock was absorbing and confining electrons to a very thin skin depth. Radio wave transmission and detection worked with every single test administered. This hypothesis was reviewed for propagating, long-wave generation with sufficient amplitude, and the capability of penetrating solid rock. Additionally, fracture spaces, either air or ion-filled, can facilitate this concept from great depths and allow for surficial detection. A few propagating precursor signals have been detected in the field occurring with associated phases using custom-built loop antennae. Field testing was conducted in Southern California from 2006-2011, and outside the NE Texas town of Timpson in February, 2013. The antennae have mobility and observations were noted for recurrence, duration, and frequency response. At the Southern California field sites, one loop antenna was positioned for omni-directional reception and also detected a strong First Schumann Resonance; however, additional Schumann Resonances were absent. At the Timpson, TX field sites, loop antennae were positioned for directional reception, due to earthquake-induced, hydraulic fracturing activity currently conducted by the oil and gas industry. Two strong signals, one moderately strong signal, and approximately 6-8 weaker signals were detected in the immediate vicinity. The three stronger signals were mapped by a biangulation technique, followed by a triangulation technique for confirmation. This was the first antenna mapping technique ever performed for determining possible earthquake epicenters. Six and a half months later, Timpson experienced two M4 (M4.1 and M4.3) earthquakes on September 2, 2013 followed by a M2.4 earthquake three days later, all occurring at a depth of five kilometers. The Timpson earthquake activity now has a cyclical rate and a forecast was given to the proper authorities. As a result, the Southern California and Timpson, TX field results led to an improved design and construction of a third prototype antenna. With a loop antenna array, a viable communication system, and continuous monitoring, a full fracture cycle can be established and observed in real-time. In addition, field data could be reviewed quickly for assessment and lead to a much more improved earthquake forecasting capability. The EM precursors determined by this method appear to surpass all prior precursor claims, and the general public will finally receive long overdue forecasting.
Induction coilgun for EM mortar
R. Kaye; B. Turman; M. Aubuchon; D. Lamppa; G. Mann; Edward van Reuth; K. Fulton; G. Malejko; P. Magnotti; D. Nguyen; D. Borgwarth; A. Johnson; R. Poppe
2007-01-01
The Defense Advanced Research Projects Agency is investigating electromagnetic (EM) guns for the next generation combat vehicle providing improved performance and survivability without the use of propellant. The two-year program was initiated in 2005 to design a coilgun and a railgun to launch an existing mortar round with an EM armature in laboratory conditions at speeds to increase range beyond
CURSO DE ESPECIALIZAO EM FISIOTERAPIA
Floeter, Sergio Ricardo
dois módulos no domingo e dois no Hospital Universitário em Florianópolis. LOCAL: Rua Pedro João. Enviar Documentação para: Universidade Federal de Santa Catarina - Campus Araranguá Rua Pedro João$ 425,00. Vencimento no 5º dia útil do mês. (1ª parcela em julho de 2012). PROGRAMA Virologia Genética
Observation of an Effective Magnetic field for Light
Tzuang, Lawrence D; Nussenzveig, Paulo; Fan, Shanhui; Lipson, Michal
2013-01-01
Photons are neutral particles that do not interact directly with a magnetic field. However, recent theoretical work has shown that an effective magnetic field for photons can exist if the phase of light would change with its propagating direction. This direction-dependent phase indicates the presence of an effective magnetic field as shown for electrons experimentally in the Aharonov-Bohm experiment. Here we replicate this experiment using photons. In order to create this effective magnetic field, we construct an on-chip silicon-based Ramsey-type interferometer. This interferometer has been traditionally used to probe the phase of atomic states, and here we apply it to probe the phase of photonic states. We experimentally observe a phase change, i.e. an effective magnetic field flux from 0 to 2pi. In an Aharonov-Bohm configuration for electrons, considering the device geometry, this flux corresponds to an effective magnetic field of 0.2 Gauss.
NASA Astrophysics Data System (ADS)
Batelaan, Herman
2007-06-01
Our group has realized a Mach-Zehnder interferometer for electron matter waves and a source of femtosecond electron pulses. In the first experiment a highly collimated electron beam passes through three gold coated nano-fabricated gratings and reveals interference fringes. Measured dephasing processes poses limitations on the low energy use of this device. In the second experiment a femtosecond laser pump-probe experiment on a field emission tip was performed. Control of the electron emission mechanisms, which are multi-photon absorption and optical field tunneling, may be useful for the production of attosecond electron pulses. We will discuss the use of the first device to test the dispersionless nature of the Aharonov-Bohm effect and the use of the second device to test the macroscopic limit of the Aharonov-Bohm effect.
Ping V. Lin; F. E. Camino; V. J. Goldman
2009-01-01
We report experiments in a large, 2.5mum diameter Fabry-Perot quantum Hall interferometer with two tunneling constrictions. Interference fringes are observed as conductance oscillations as a function of applied magnetic field (the Aharonov-Bohm flux through the electron island) or a global backgate voltage (electronic charge in the island). Depletion is such that in the fractional quantum Hall regime, filling 1\\/3 current-carrying
Ping V. Lin; F. E. Camino; V. J. Goldman
2009-01-01
We report experiments in a large, 2.5 Î¼m diameter Fabry-Perot quantum Hall interferometer with two tunneling constrictions. Interference fringes are observed as conductance oscillations as a function of applied magnetic field (the Aharonov-Bohm flux through the electron island) or a global backgate voltage (electronic charge in the island). Depletion is such that in the fractional quantum Hall regime, filling 1\\/3
Maxwell Duality, Lorentz Invariance, and Topological Phase
Jonathan P. Dowling; Colin P. Williams; J. D. Franson
1999-08-06
We discuss the Maxwell electromagnetic duality relations between the Aharonov-Bohm, Aharonov-Casher, and He-McKellar-Wilkens topological phases, which allows a unified description of all three phenomena. We also elucidate Lorentz transformations that allow these effects to be understood in an intuitive fashion in the rest frame of the moving quantum particle. Finally, we propose two experimental schemes for measuring the He-McKellar-Wilkens phase.
Microwave guiding of electrons on a chip
Johannes Hoffrogge; Roman Fröhlich; Mark A. Kasevich; Peter Hommelhoff
2010-01-01
Electrons travelling in free space have allowed to explore fundamental\\u000aphysics like the wave nature of matter, the Aharonov-Bohm and the Hanbury\\u000aBrown-Twiss effect. Complementarily, the precise control over the external\\u000adegrees of freedom of electrons has proven pivotal for wholly new types of\\u000aexperiments such as high precision measurements of the electron's mass and\\u000amagnetic moment in Penning traps.
Aharonov-Casher effect in massive-photon electrodynamics
Christopher Fuchs
1990-01-01
In concurrence with a recent calculation for the Aharonov-Bohm effect by Boulware and Deser, it is shown that the Aharonov-Casher phase shift for a neutral magnetic dipole diffracted around a uniform infinitely long line charge still occurs in massive-photon electrodynamics. This effect reduces smoothly to the original in the limit that the photon mass vanishes. Unlike the case for the
Photon-assisted tunneling through open mesoscopic rings threaded by time-periodic magnetic fluxes
Cong Hua Yan; Lian Fu Wei
2010-01-01
Quantum waveguide theories have been successfully applied to various time-independent ballistic transports in mesoscopic structures, including typically the Aharonov-Bohm rings. Here, we consider the quantum transport along the one-dimensional electron structures driven by time-dependent external fields, typical the open mesoscopic rings threaded by time-periodic magnetic fluxes. Based on the well-known Floquet theorem we effectively separate the time and space variables
Devoret, Michel H.
Aharonov-Bohm effect," which should be observable in the shot noise of a phase-coherent conduc- tor under and the I-V curve are unaffected. The observed effect bears a strong resemblance to photonVOLUME 80, NUMBER 11 P H Y S I C A L R E V I E W L E T T E R S 16 MARCH 1998 Observation of "Photon
Photon-assisted tunneling through open mesoscopic rings threaded by time-periodic magnetic fluxes
Cong Hua Yan; Lian Fu Wei
2010-01-01
Quantum waveguide theories have been successfully applied to various time-independent ballistic transports in mesoscopic structures, including typically the Aharonov–Bohm rings. Here, we consider the quantum transport along the one-dimensional electron structures driven by time-dependent external fields, typical the open mesoscopic rings threaded by time-periodic magnetic fluxes. Based on the well-known Floquet theorem we effectively separate the time and space variables
An AB effect without closing a loop
A. Retzker; Y. Aharonov; A. Botero; S. Nussinov; B. Reznik
2005-01-01
We discuss the consequences of the Aharonov-Bohm effect in setups involving\\u000aseveral charged particles, wherein none of the charged particles encloses a\\u000aclosed loop around the magnetic flux. We show that in such setups, the AB phase\\u000ais encoded either in the relative phase of a bi-partite or multi-partite\\u000aentangled photons states, or alternatively, gives rise to an overall AB
Brandon Langley; Marko Zivkovic; Ivana Djuric
2010-01-01
We examine a ballistic electron Aharonov-Bohm interferometer with a single dot embedded in each of two arms that are connected in parallel to leads allowing the flow of current by sequential tunneling of electrons through the dots. We focus on the effect that correlations between dots due to the inter-dot spin-spin interactions have on the current-voltage(I-V) and frequency dependent current
Time-dependent resonant tunnelling for parallel-coupled double quantum dots
Bing Dong; Ivana Djuric; H. L. Cui; X. L. Lei
2004-01-01
We derive the quantum rate equations for an Aharonov–Bohm interferometer with two vertically coupled quantum dots embedded in each of two arms by means of the nonequilibrium Green function in the sequential tunnelling regime. Based on these equations, we investigate time-dependent resonant tunnelling under a small amplitude irradiation and find that the resonant photon-assisted tunnelling peaks in photocurrent demonstrate a
Basic quantum mechanical concepts from the operational viewpoint
D N Klyshko
1998-01-01
The physical meaning of the basic quantum mechanical concepts (such as the wave function, reduction, state preparation and measurement, the projection postulate, and the uncertainty principle) is clarified using realistic experimental procedures and employing classical analogies whenever possible. Photon polarization measurement and particle coordinate and momentum measurement are considered as examples, as also are Einstein–Podolsky–Rosen correlations, Aharonov–Bohm effects, quantum teleportation,
Preface pagexiii How to use this book xv
Paris-Sud 11, Université de
.1 Interference and disorder 1 1.2 The AharonovBohm effect 4 1.3 Phase coherence and the effect of disorder 7 1.cambridge.org Cambridge University Press 978-0-521-85512-9 - Mesoscopic Physics of Electrons and Photons Eric Akkermans and Gilles Montambaux Table of Contents More information #12;vi Contents A2.3.2 Mie scattering 60 A2.3.3 Atomphoton
Spin-flip mesoscopic transport through a toroidal carbon nanotube coupled to normal metal terminals
Hong-Kang Zhao; Qing Wang
2005-01-01
The spin and charge currents tunnelling through coupled toroidal carbon nanotube (TCN) system is investigated in the presence of rotating magnetic field and an Aharonov–Bohm magnetic flux. The charge current and spin current coexist in the same system as eV?0. The charge conductance, charge current, and spin current are sensitively determined by the applied magnetic fields and the quantum nature
Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation
Altschul; Brett
2007-01-01
If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10â»Â³Â²e level if all photons have the same charge and 10â»â´â¶e if different photons can carry different charges.
Tanmay Vachaspati; Daniele A. Steer
2011-01-01
The time-dependent metric of a cosmic string leads to an effective interaction between the string and photons--the ''gravitational Aharonov-Bohm'' effect--and causes cosmic strings to emit light. We evaluate the radiation of pairs of photons from cosmic strings and find that the emission from cusps, kinks and kink-kink collisions occurs with a flat spectrum at all frequencies up to the string
Danièle A. Steer; Tanmay Vachaspati
2011-01-01
The time-dependent metric of a cosmic string leads to an effective interaction between the string and photons---the ``gravitational Aharonov-Bohm'' effect---and causes cosmic strings to emit light. We evaluate the radiation of pairs of photons from cosmic strings and find that the emission from cusps, kinks and kink-kink collisions occurs with a flat spectrum at all frequencies up to the string
Slow Photons as Charged Quasi-Particles
Marzlin, K -P; Lvovsky, A I
2007-01-01
We propose a scheme that allows generating geometric effects in the propagation of light through an atomic ensemble exhibiting electromagnetically induced transparency. Inhomogeneities in the control laser fields induce an artificial gauge potential to which the signal field is coupled akin to a charged particle in electrodynamics. We discuss applications of this phenomenon which include constant electric and magnetic quasi-fields and an Aharonov-Bohm potential for photons.
Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation
NASA Astrophysics Data System (ADS)
Altschul, Brett
2007-06-01
If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10-32e level if all photons have the same charge and 10-46e if different photons can carry different charges.
REVIEWS OF TOPICAL PROBLEMS: Basic quantum mechanical concepts from the operational viewpoint
D. N. Klyshko
1998-01-01
The physical meaning of the basic quantum mechanical concepts (such as the wave function, reduction, state preparation and measurement, the projection postulate, and the uncertainty principle) is clarified using realistic experimental procedures and employing classical analogies whenever possible. Photon polarization measurement and particle coordinate and momentum measurement are considered as examples, as also are Einstein-Podolsky-Rosen correlations, Aharonov-Bohm effects, quantum teleportation,
Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation
Brett Altschul
2007-06-29
If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10^(-32) e level if all photons have the same charge and 10^(-46) e if different photons can carry different charges.
Quantum Phase Shift Caused by Spatial Confinement
B. E. Allman; A. Cimmino; S. L. Griffin; A. G. Klein
1999-01-01
This paper presents the results of optical interferometry experiments in which the phase of photons in one arm of a Mach-Zehnder interferometer is modified by applying a transverse constriction. An equivalent quantum interferometry experiment using neutron de Broglie waves is discussed in which the observed phase shift is in the spirit of the force-free phase shift of the Aharonov-Bohm effects.
Remarks on Aharanov-Bohm effect and geometric phase
S. C. Tiwari
2004-01-01
Recently the physical mechanism for geometric phase in optics has been\\u000aelucidated in terms of the angular momentum holonomy proposed in 1992. Aharonov\\u000aand Kaufherr (PRL, 92, 070404, 2004) revisit the Aharonov-Bohm effect, and\\u000apropose non-local exchange of a conserved, gauge invariant quantity that\\u000achanges the modular momentum of the particle that is responsible for the AB\\u000aphase shift. We
Bound on the Photon Charge from the Phase Coherence of Extragalactic Radiation
Brett Altschul
2007-01-01
If the photon possessed a nonzero charge, then electromagnetic waves traveling along different paths would acquire Aharonov-Bohm phase differences. The fact that such an effect has not hindered interferometric astronomy places a bound on the photon charge estimated to be at the 10-32e level if all photons have the same charge and 10-46e if different photons can carry different charges.
An Exact Expression for a Flat Connection on the Complement of a Torus Knot
V. V. Sreedhar
2015-01-08
Simple physics ideas are used to derive an exact expression for a flat connection on the complement of a torus knot. The result is of some mathematical importance in the context of constructing representations of the knot group -- a topological invariant of the knot. It is also a step forward in the direction of obtaining a generalisation of the Aharonov-Bohm effect, in which charged particles moving through force-free regions are scattered by impenetrable, knotted solenoids.
Magnetic properties of a two-electron quantum dot
C. E. Creffield; J. H. Jefferson; S. Sarkar; D. L. Tipton
1999-01-01
The low-energy eigenstates of two interacting electrons in a square quantum\\u000adot in a magnetic field are determined by numerical diagonalization. In the\\u000astrong correlation regime, the low-energy eigenstates show Aharonov-Bohm type\\u000aoscillations, which decrease in amplitude as the field increases. These\\u000aoscillations, including the decrease in amplitude, may be reproduced to good\\u000aaccuracy by an extended Hubbard model in
Magnetic field dependence of the low-energy spectrum of a two-electron quantum dot
C. E. Creffield; J. H. Jefferson; Sarben Sarkar; D. L. J. Tipton
2000-01-01
The low-energy eigenstates of two interacting electrons in a square quantum dot in a magnetic field are determined by numerical diagonalization. In the strong correlation regime, the low-energy eigenstates show Aharonov-Bohm-type oscillations, which decrease in amplitude as the field increases. These oscillations, including the decrease in amplitude, may be reproduced to good accuracy by an extended Hubbard model in a
Magnetic properties of a two-electron quantum dot
C. E. Creffield; J. H. Jefferson; S. Sarkar; D. L. Tipton
1999-01-01
The low-energy eigenstates of two interacting electrons in a square quantum dot in a magnetic field are determined by numerical diagonalization. In the strong correlation regime, the low-energy eigenstates show Aharonov-Bohm type oscillations, which decrease in amplitude as the field increases. These oscillations, including the decrease in amplitude, may be reproduced to good accuracy by an extended Hubbard model in
Observation of a topological phase by means of a nonplanar Mach-Zehnder interferometer
R. Y. Chiao; A. Antaramian; K. M. Ganga; H. Jiao; S. R. Wilkinson; H. Nathel
1988-01-01
We report the direct observation of a topological phase, i.e., an Aharonov-Bohm-type phase, as a fringe shift in an optical interferometer, which consisted of a modified Mach-Zehnder interferometer, in which the light traveled along nonplanar paths in its two arms. These arms were arranged symmetrically so as to have nearly equal path lengths, but opposite senses of handedness. The relationship
Asymmetric coherent transmission for single particle diode and gyroscope
S. Yang; Z. Song; C. P. Sun
2009-01-01
We study the single particle scattering process in a coherent multi-site system consisting of a tight-binding ring threaded by an Aharonov-Bohm flux and several attaching leads. The asymmetric behavior of scattering matrix is discovered analytically in the framework of both Bethe Ansatz and Green's function formalism. It is found that, under certain conditions, a three-site electronic system can behave analogous
Is magnetic flux quantized inside a solenoid?
F. Darabi
2009-01-13
In some textbooks on quantum mechanics, the description of flux quantization in a superconductor ring based on the Aharonov-Bohm effect may lead some readers to a (wrong) conclusion that flux quantization occurs as well for a long solenoid with the same quantization condition in which the charge of cooper pair $2e$ is replaced by the charge of one electron $e$. It is shown how this confusion arises and how can one avoid it.
Probe-configuration-dependent dephasing in a mesoscopic interferometer
NASA Astrophysics Data System (ADS)
Seelig, G.; Pilgram, S.; Jordan, A. N.; Büttiker, M.
2003-10-01
Dephasing in a ballistic four-terminal Aharonov-Bohm geometry due to charge and voltage fluctuations is investigated. Treating two terminals as voltage probes, we find a strong dependence of the dephasing rate on the probe configuration in agreement with a recent experiment by Kobayashi, Aikawa, Katsumoto, and Iye [J. Phys. Soc. Jpn. 71, 2094 (2002)]. Voltage fluctuations in the measurement circuit are shown to be the source of the configuration dependence.
Decoherence in Ballistic Mesoscopic Interferometers
NASA Astrophysics Data System (ADS)
Seelig, Georg; Pilgram, Sebastian; Büttiker, Markus
2003-09-01
We provide a theoretical explanation for two recent experiments on decoherence of Aharonov-Bohm oscillations in two- and multi-terminal ballistic rings. We consider decoherence due to charge fluctuations and emphasize the role of charge exchange between the system and the reservoir or nearby gates. A time-dependent scattering matrix approach is shown to be a convenient tool for the discussion of decoherence in ballistic conductors.
College of Engineering EM Engineering Mechanics
MacAdam, Keith
College of Engineering EM Engineering Mechanics KEY: # = new course * = course changed = course or concur: MA 213. EM 302 MECHANICS OF DEFORMABLE SOLIDS. (3 of Engineering or consent of chairperson, and EM 221; prereq or concur: MA 214. EM 313 DYNAMICS. (3
Dicas para cruzeiros Todos os anos, milhes de cidados americanos saem em cruzeiros de frias. Em
Dicas para cruzeiros Todos os anos, milhões de cidadãos americanos saem em cruzeiros de férias. Em 2003, aproximadamente 8,3 milhões de passageiros embarcaram em diversos portos norte-americanos em cruzeiros de férias (fonte: Cruise Lines International Association). As viagens em navios de cruzeiro expõem
Investigao em clulas estaminais no Biocant deu origem a cinco patentes em dois anos
Instituto de Sistemas e Robotica
Investigação em células estaminais no Biocant deu origem a cinco patentes em dois anos A investigação em células estaminais (do cordão umbilical) no parque tecnológico Biocant, em Cantanhede, resultou, nos últimos dois anos, em cinco patentes, duas delas já licenciadas a empresas, disse à Lusa o
Anlise do desmatamento em 2009, em especial em municpios e reas
em Outros Usos - 2.000 4.000 6.000 8.000 10.000 12.000 14.000 16.000 18.000 20.000 2001 2002 2003 desmatamento em Glebas - 2.000 4.000 6.000 8.000 10.000 12.000 14.000 16.000 18.000 20.000 2001 2002 2003 2004 2005 2006 2007 2008 2009 Histórico do desmatamento em Assentamentos - 2.000 4.000 6.000 8.000 10.000 12.000
Li, Zhaoping; Summanen, Paula H; Downes, Julia; Corbett, Karen; Komoriya, Tomoe; Henning, Susanne M; Kim, Jenny; Finegold, Sydney M
2015-06-01
We used pomegranate extract (POMx), pomegranate juice (POM juice) and green tea extract (GT) to establish in vitro activities against bacteria implicated in the pathogenesis of acne. Minimum inhibitory concentrations (MIC) of 94 <em>Propionibacterium acnes, Propionibacterium granulosum, Staphylococcus aureus,em> and <em>Staphylococcus epidermidisem> strains were determined by Clinical and Laboratory Standards Institute-approved agar dilution technique. Total phenolics content of the phytochemicals was determined using the Folin-Ciocalteu method and the polyphenol composition by HPLC. Bacteria were identified by 16S rRNA sequence analysis. GT MIC of 400 ?g/ml or less was obtained for 98% of the strains tested. 64% of <em>P. acnesem> strains had POMx MICs at 50 ?g/ml whereas 36% had MIC >400 ?g/ml. POMx, POM juice, and GT showed inhibitory activity against all the <em>P. granulosumem> strains at ?100 ?g/ml. POMx and GT inhibited all the <em>S. aureusem> strains at 400 ?g/ml or below, and POM juice had an MIC of 200 ?g/ml against 17 <em>S. aureusem> strains. POMx inhibited <em>S. epidermidisem> strains at 25 ?g/ml, whereas POM juice MICs were ?200 ?g/ml. The antibacterial properties of POMx and GT on the most common bacteria associated with the development and progression of acne suggest that these extracts may offer a better preventative/therapeutic regimen with fewer side effects than those currently available.
<em>J Drugs Dermatolem>. 2015;14(6):574-578. PMID:26091382
MESTRADO EM MICROBIOLOGIA TAXONOMIA MICROBIANA Faculdade de Cincias
Instituto de Sistemas e Robotica
MESTRADO EM MICROBIOLOGIA TAXONOMIA MICROBIANA Faculdade de Ciências Objectivos: O principal e métodos utilizados em taxonomia microbiana (em particular de procariotas), encarada nas suas/diagnóstico utilizados actualmente em taxonomia bacteriana. Constituem objectivos adicionais a discussão da
Populações estelares em galáxias HII
NASA Astrophysics Data System (ADS)
Westera, P.; Cuisinier, F.; Telles, E.; Kehrig, C.
2003-08-01
Analisamos o conteúdo estelar de 74 galáxias HII a partir do contínuo observado nos espectros ópticos dessas galáxias, utilizando métodos de síntese de população estelar. Descobrimos que todas as galáxias para as quais encontramos soluções contêm uma população estelar velha que domina a massa estelar, e numa maioria dessas também encontramos evidência de uma população de idade intermediaria além da geração jovem que está se formando agora. Concluímos que a formação estelar dessas galáxias se realiza em surtos individuais, Esses surtos são interrompidos por longos períodos de inatividade, com os primeiros consumindo a maior parte do gás. Sugerimos, portanto, que as galáxias HII sejam galáxias anãs normais flagradas em um período de surto.
ESTUDO DO MEIO EM UMESTUDO DO MEIO EM UM BAIRRO POPULAR NABAIRRO POPULAR NA
ESTUDO DO MEIO EM UMESTUDO DO MEIO EM UM BAIRRO POPULAR NABAIRRO POPULAR NA CIDADE DECIDADE DE DIDÁTICA EM QUE CONSITE O NOSSOEM QUE CONSITE O NOSSO PROJETO?PROJETO? MATERIAISMATERIAIS CAPACITAÇÃO PARTICIPATIVOORÇAMENTO PARTICIPATIVO #12;ALGUNS PROBLEMASALGUNS PROBLEMAS PROJETOS FUTUROSPROJETOS FUTUROS COORDENAÇÃO EM
EM and Stochastic EM algorithms for reliability mixture models under random censoring
Paris-Sud XI, Université de
EM and Stochastic EM algorithms for reliability mixture models under random censoring Laurent.chauveau@univ-orleans.fr April 6, 2012 Abstract We present in this paper several iterative methods based on EM and Stochas- tic EM methodology, that allow to estimate parametric or semiparametric mix- ture models for randomly
Wildson L. P. Santos; Patrícia F. L. Machado; Roseli T. Matsunaga; Elton L. Silva; Erlete S. Vasconcellos; Valéria R. Santana
2010-01-01
Neste artigo, são apresentados resultados obtidos em quatro estudos de casos sobre a introdução de educação ambiental em uma visão socioambiental em aulas de Química. A discussão dos resultados levanta reflexões sobre perspectivas e desafios para a educação ambiental no ensino de Química. São demonstradas sugestões de atividades possíveis de serem desenvolvidas em aulas de Químicas. Várias fontes de dados
Review -EM Waves Wavelengths of 108 to
Bertulani, Carlos A. - Department of Physics and Astronomy, Texas A&M University
#12;Review - EM Waves EM Waves Wavelengths of 108 to 10-16 meters (10-1024 Hz) Traveling wave) given by BES rrr ×= 0 1 )(sin 111 22 0 2 00 tkxE c E c EBS m -=== Review - EM Waves 2 0 1 mpeak E c pr = c I pr = c I pr 2 = Total absorption Total reflection EM Waves: Radiation pressure #12;Source
PRMIO PRIMUS INTER PARES Construir em equipa
Instituto de Sistemas e Robotica
PRÉMIO PRIMUS INTER PARES Construir em equipa as lideranças futuras 24 jovens testam competências na semifinal, em Peniche. Só um será o primeiro entre os seus pares Primeiro exercício da semifinal, como o imagi- nam. Como vão poder resumir o seu percurso profissional daqui a 25 anos, em 2038? Nas
Pesquisas em Astrofsica no Oswaldo Duarte Miranda
Pesquisas em Astrofísica no INPE Oswaldo Duarte Miranda Divisão de Astrofísica DAS #12 sua influência na magnetosfera terrestre. Abaixo: mapa do Sol em 22 GHz #12; Física do Meio Investigações são feitas através de observações em várias faixas do espectro eletromagnético, utilizandose
Halibut/Sablefish EM Pilot Project
Halibut/Sablefish EM Pilot Project A Collaboration Involving: · Alaska Longline Fishermen's Assn · Engage stakeholders in developing a workable at-sea monitoring program · Field test EM hardware effective means of deploying EM hardware among vessels and retrieving data · Summarize study findings
Falta de investimento prejudica sector em Portugal
Instituto de Sistemas e Robotica
Falta de investimento prejudica sector em Portugal O país tem bons profissionais e potencialidades comunidade científica, em aplicar os conhecimentos na área e Portugal "tem uma boa infra-estrutura humana e, mas em Portugal investe-se apenas nos três primeiros anos - leva muitos investigadores a desistir
Segurana em Sistemas Distribudos confidencialidade
Rodriguez, Noemi
chamada de segredo compartilhado · também chamada de criptografia simétrica criptografar texto chaves secretas · como fazer para as duas partes compartilharem um segredo? · uso de Key Distribution conceito com Diffie-Hellman, em 1976 D-H apenas para estabelecimento de segredo compartilhado
Instituto de Sistemas e Robotica
Página Inicial Empresas Start-ups portuguesas mostram-se hoje a investidores suecos em Lisboa Empresas criadas em Portugal atingem as 31.400 em 2012 e superam... As empresas criadas em Portugal ascenderam a 31.400 em 2012, superando os... REGISTO | COMUNIDADE | Insolvência de empresas aumentou 41% em
Floeter, Sergio Ricardo
Aprovado pelo Colegiado do Curso de Pós-Graduação em Farmacologia em 16 de Julho de 1999. REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM FARMACOLOGIA DO CENTRO DE CIÊNCIAS BIOLÓGICAS DA UNIVERSIDADE FEDERAL DE SANTA CATARINA CAPÍTULO I SEÇÃO I DO OBJETIVO Art. 1o - O Curso de Pós-Graduação em Farmacologia em
Angus Robichaud's Reel G Em D A Bm D7
Doyle, Peter
Angus Robichaud's Reel 4 4 D G A D D G A D 3 3 G Em D A Bm D7 3 3 G Em D A D Animas Reel Bernie Waugh 4 4 3 3 G D G Bm Em C Am C D G D G Bm Em C Am D G The Arkansas Traveler 4 2 D G A D Em A 3 D G A D Em G A D D G D A Bm Em A D G D A Em G A D #12; Asher Rodney Miller 4 4 D Em F#m G A D Em G A D A D 1
Angus Robichaud's Reel G Em D A Bm D7
Doyle, Peter
Angus Robichaud's Reel 4 4 D G A D D G A D 3 3 G Em D A Bm D7 3 3 G Em D A D Animas Reel Bernie Waugh 4 4 3 3 G D G Bm Em C Am C D G D G Bm Em C Am D G The Arkansas Traveler 4 2 D G A D Em A 3D G A D Em G A D D G D A Bm Em A D G D A Em G A D #12;Asher Rodney Miller 4 4 D Em F#m G A D Em G A D A D1 2
Development of an EMS curriculum.
Brice, Jane H; Perina, Debra G; Liu, J Marc; Braude, Darren A; Rinnert, Kathy J; MacDonald, Russell D
2014-01-01
Emergency medical services (EMS) became an American Board of Medical Specialties (ABMS) approved subspecialty of emergency medicine in September 2010. Achieving specialty or subspecialty recognition in an area of medical practice requires a unique body of knowledge, a scientific basis for the practice, a significant number of physicians who dedicate a portion of their practice to the area, and a sufficient number of fellowship programs. To prepare EMS fellows for successful completion of fellowship training, a lifetime of subspecialty practice, and certification examination, a formalized structured fellowship curriculum is necessary. A functional curriculum is one that takes the entire body of knowledge necessary to appropriately practice in the identified area and codifies it into a training blueprint to ensure that all of the items are covered over the prescribed training period. A curriculum can be as detailed as desired but typically all major headings and subheadings of the core content are identified and addressed. Common curricular components, specific to each area of the core content, include goals and objectives, implementation methods, evaluation, and outcomes assessment methods. Implementation methods can include simulation, observations, didactics, and experiential elements. Evaluation and outcomes assessment methods can include direct observation of patient assessment and treatment skills, structured patient simulations, 360° feedback, written and oral testing, and retrospective chart reviews. This paper describes a curriculum that is congruent with the current EMS core content, as well as providing a 12-month format to deploy the curriculum in an EMS fellowship program. Key words: curriculum; education; emergency medical services; fellowships and scholarships. PMID:24156509
Complaints against an EMS system.
Colwell, Christopher B; Pons, Peter T; Pi, Randy
2003-11-01
Complaints against Emergency Medical Services (EMS) agencies represent a concerning and potentially time-consuming problem for all involved in the delivery of prehospital emergency medical care. The objective of this study was to identify the source of complaints against an EMS system to help focus quality and performance improvement and customer service efforts. We conducted a retrospective review of complaints filed against a busy urban EMS agency over a 6-year period. All complaints were included, totaled by season and by year, and categorized by originator and nature of the complaint. A total of 286 complaints were registered during the 6-year period, with an average of 48 per year and 9.3 per 10,000 responses. The most common originators of complaints were patients (53%) followed by medical personnel (19%) and family members or friends (12%). Rude behavior accounted for 23% of the complaints registered, followed by technical skills (20%), transport problems (18%), and loss of belongings (13%). The identification of areas of dissatisfaction will allow focused quality and performance improvement programs directed at customer service and risk management. PMID:14654181
POLMEROS EM SUPERFCIES Polmeros adsorvidos na superfcies de partculas
Loh, Watson
POLÍMEROS EM SUPERFÍCIES Polímeros adsorvidos na superfícies de partículas coloidais Polímeros em interfaces líquidas Polímeros em interfaces sólidas #12;Polímeros em solução - Teoria de Flory-Hugghins #12;Polímeros em solução - Teoria de Flory-Hugghins Gm = kT(1ln1 + 2/N ln2 + 12) 1 = solvente 2 = polímero (Gm
Random swap EM algorithm for Gaussian mixture models Qinpei Zhao
Joensuu, University of
Random swap EM algorithm for Gaussian mixture models Qinpei Zhao , Ville HautamÃ¤ki, Ismo. Borgefors Keywords: Expectation maximization Random swap EM Gaussian mixture model Split and merge EM Genetic-based EM Data clustering a b s t r a c t Expectation maximization (EM) algorithm is a popular way
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM CIÊNCIA E, França, 2003 #12;2 CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM para o Mestrado (*) CMS-207-4 Técnicas Experimentais em Ciência dos Materiais I CMS-300-4 Mecânica
Lietuvos teritorijos žem?s plutos deformacij? ir seismotektoninio potencialo ryšys
NASA Astrophysics Data System (ADS)
Zakarevi?ius, Algimantas; Stanionis, Arminas; Levinskait?, Daiva
2010-01-01
Lietuvoje yra statini?, kelian?i? ekologinio pavojaus gr?sm? (Ignalinos atomin? elektrin?, Mažeiki? naftos perdirbimo ?mon?, chemijos gamyklos Jonavoje bei K?dainiuose ir pan.). Seisminiai ?vykiai gali sutrikdyti ši? ?moni? veikl? ir net lemti didel? pavoj? aplinkai, t. y. gali b?ti sukelta didel? aplinkos tarša chemin?mis bei radioaktyviosiomis medžiagomis. Seisminius ?vykius lemia teritorijos seismotektoninis potencialas. Seismotektoninis potencialas ir Žem?s plutos deformacijos yra tarpusavyje susij? rei\\vskiniai, kuriuos sukelia dažnai tie patys giluminiai procesai Žem?s gelm?se. Žem?s plutos deformacij? tyrimas yra vienas iš informacijos šaltini? prognozuojant teritorijos seismotektonin? aktyvum?. Straipsnyje nagrin?jamos Žem?s plutos horizontaliosios deformacijos, nustatomi Žem?s plutos ?tempi? poky?iai Lietuvos teritorijoje pagal GPS matavim? duomenis. Atlikus tyrimus pagal pateikiam? Žem?s plutos horizontali?j? deformacij? ir ?tempi? tyrimo metodik?, gauti nauji horizontali?j? deformacij? charakteristik? bei ?tempi? poky?i? rezultatai ir nustatytos j? s?sajos su seismotektoniniu potencialu.
Servidor tem direito a licena para acompanha cnjuge aprovado em concurso em outro estado
Floeter, Sergio Ricardo
Servidor tem direito a licença para acompanha cônjuge aprovado em concurso em outro estado O servidor público tem direito a licença para acompanhamento do cônjuge se este for aprovado em concurso Federal da 4ª Região (TRF4), o tribunal concedeu apenas o direito a licença não-remunerada, mas não
Disperses leo em gua (o/w) ou gua em leo (w/o) Fase contnua / fase dispersa.
Loh, Watson
Emulsões Dispersões óleo em água (o/w) ou água em óleo (w/o) Fase contínua / fase dispersa. Agente solubilidade da fase dispersa em gotas menores - "Ostwald Ripening" mais pronunciado em fases mais miscíveis) SLES/betaína (b)- inverso #12;3. Barreira eletrostática ou estérica Repulsão eletrostática em
dos Santos, C.A.
Em 1959 cursava o terceiro colegial no Julinho em Porto Alegre, onde recebi o folheto "Você tem pensado em física?" que mais tarde soube ter sido produzido pelo Darcy. Estava indeciso entre física e som e a cores a bela tarde em que, dentro de um bonde Petrópolis, passando pela Protásio diante do
O ESPAÇO DA UVA TRANSFORMADO EM AGRONEGÓCIO
Mariza Cezira Campagner; Gervasio Castro de Rezende
2008-01-01
O presente artigo tem por objetivo apresentar algumas das redefinições do trabalho agrícola resultantes do processo de reestruturação do espaço da uva transformado em agronegócio, no qual se tem expandido o agronegócio de frutas tropicais. A metodologia está organizada em torno de atualização da pesquisa bibliográfica e as temáticas de interesse; realização de trabalhos na área de estudo. Conclui que
CURSO DE PS-GRADUAO EM METEOROLOGIA
CURSO DE PÓS-GRADUAÇÃO EM METEOROLOGIA Coordenador Acadêmico Dirceu Luis Herdies Membros do Conselho de Curso Luis Gustavo Gonçalves de Gonçalves José Antonio Marengo Orsini Clóvis Angeli Sansigolo Innocentini, Ph.D., Univ. of Reading, 1986 #12;2 CURSO DE PÓS-GRADUAÇÃO EM METEOROLOGIA PROGRAMAÇÃO ANUAL DAS
CURSO DE PS-GRADUAO EM METEOROLOGIA
CURSO DE PÓS-GRADUAÇÃO EM METEOROLOGIA Coordenadora Acadêmica Maria Paulete Pereira Martins Membros do Conselho de Curso Dirceu Luis Herdies Luis Gustavo Gonçalves de Gonçalves José Antonio Marengo., 1969 Valdir Innocentini, Ph.D., Univ. of Reading, 1986 #12;2 CURSO DE PÓS-GRADUAÇÃO EM METEOROLOGIA
TR-IIS-07-012 aEM: Targeted Aggressive
Chen, Sheng-Wei
. (1997) proposed the parameterized EM (pEM) algorithm to accelerate EM for Bayesian Networks, and Luis and Leslie (1999) applied pEM for Mixtures of Gaussians. The pEM algorithm accelerates the convergence . They showed that pEM converges faster than EM and the convergence is guaranteed when 1 pEM
M em ory for Item s and M em ory for R elations in the Procedural/D eclarative M em ory Fram ew ork
Poldrack, Russ
M em ory for Item s and M em ory for R elations in the Procedural/D eclarative M em ory Fram ew ork ard Eichenbaum Boston U niversity, U SA A m ajor area of research in m em ory and am nesia concerns the item specificity of im plicit m em ory. In this paper w e address several issues about the nature of im
EM International, July 1994, Volume 2
Not Available
1994-10-01
The Office of Environmental Management (EM) at the Department of Energy (DOE) is seeking out and leveraging foreign technology, data, and resources in keeping with EM`s mandate to protect public health and the environment through the safe and cost-effective remediation of the Department`s nuclear weapons sites. EM works closely with foreign governments, industry, and universities to obtain innovative environmental technologies, scientific and engineering expertise, and operations experience that will support EM`s objectives. Where appropriate, these international resources are used to manage the more urgent risks at our sites, secure a safe workplace, help build consensus on critical issues, and strengthen our technology development program. Through international agreements EM engages in cooperative exchange of information, technology, and individuals. Currently, we are managing agreements with a dozen countries in Europe, Latin America, and Asia. These agreements focus on environmental restoration, waste management, transportation of radioactive wastes, and decontamination and decommissioning. This publication contains the following articles: in situ remediation integrated program; in-situ characterization and inspection of tanks; multimedia environmental pollutant assessment system (MEPAS); LLNL wet oxidation -- AEA technology. Besides these articles, this publication covers: EU activities with Russia; technology transfer activities; and international organization activities.
EM Algorithms from a Non-Stochastic Perspective Charles Byrne
Byrne, Charles
EM Algorithms from a Non-Stochastic Perspective Charles Byrne August 27, 2013 Abstract The EM for estimat- ing parameters in statistics, the essence of the EM algorithm is not stochastic. The conventional formulation of the EM algorithm given in many texts and papers on the subject is inadequate. A new formulation
EM Algorithms Charles Byrne (Charles Byrne@uml.edu)
Byrne, Charles
EM Algorithms Charles Byrne (Charles Byrne@uml.edu) Department of Mathematical Sciences University of Massachusetts Lowell Lowell, MA 01854, USA March 6, 2011 Abstract The EM algorithm is not a single algorithm algorithm based on the EM framework we refer to as an "EM algorithm". Because there is no inclusive theory
On the Geometry of EM algorithms David R. Hunter
Hunter, David
of the parameter. Key Words: EM algorithm, MM algorithm 1 Introduction The term "EM algorithm" has been aroundOn the Geometry of EM algorithms David R. Hunter Technical report no. 0303 Department of Statistics that underlies all EM algorithms gives an appreciation for certain aspects of their behavior. Using several
EMS offshore. A new horizon for paramedics.
Mallard, A S
1991-10-01
The difficulty in getting medical aid to offshore drilling platforms can be a source of life-threatening delays. Recently, some companies have charted new waters by actually stationing EMS crews on their rigs. PMID:10116023
Dakshi Agrawal; Bruce Archambeault; Josyula R. Rao; Pankaj Rohatgi
2002-01-01
We present results of a systematic investigation of leakage of compromising information via electromagnetic (EM) emanations\\u000a from CMOS devices. These emanations are shown to consist of a multiplicity of signals, each leaking somewhat different information\\u000a about the underlying computation. We show that not only can EM emanations be used to attack cryptographic devices where the\\u000a power side-channel is unavailable, they
Interference between two indistinguishable electrons from independent sources
NASA Astrophysics Data System (ADS)
Neder, I.; Ofek, N.; Chung, Y.; Heiblum, M.; Mahalu, D.; Umansky, V.
2007-07-01
Very much like the ubiquitous quantum interference of a single particle with itself, quantum interference of two independent, but indistinguishable, particles is also possible. For a single particle, the interference is between the amplitudes of the particle's wavefunctions, whereas the interference between two particles is a direct result of quantum exchange statistics. Such interference is observed only in the joint probability of finding the particles in two separated detectors, after they were injected from two spatially separated and independent sources. Experimental realizations of two-particle interferometers have been proposed; in these proposals it was shown that such correlations are a direct signature of quantum entanglement between the spatial degrees of freedom of the two particles (`orbital entanglement'), even though they do not interact with each other. In optics, experiments using indistinguishable pairs of photons encountered difficulties in generating pairs of independent photons and synchronizing their arrival times; thus they have concentrated on detecting bunching of photons (bosons) by coincidence measurements. Similar experiments with electrons are rather scarce. Cross-correlation measurements between partitioned currents, emanating from one source, yielded similar information to that obtained from auto-correlation (shot noise) measurements. The proposal of ref. 3 is an electronic analogue to the historical Hanbury Brown and Twiss experiment with classical light. It is based on the electronic Mach-Zehnder interferometer that uses edge channels in the quantum Hall effect regime. Here we implement such an interferometer. We partitioned two independent and mutually incoherent electron beams into two trajectories, so that the combined four trajectories enclosed an Aharonov-Bohm flux. Although individual currents and their fluctuations (shot noise measured by auto-correlation) were found to be independent of the Aharonov-Bohm flux, the cross-correlation between current fluctuations at two opposite points across the device exhibited strong Aharonov-Bohm oscillations, suggesting orbital entanglement between the two electron beams.
Wolfe, Patrick J.
EM results from the simulation EM results on a real data Gibbs results from the simulation, 2010 #12;EM results from the simulation EM results on a real data Gibbs results from the simulation are and µ. #12;EM results from the simulation EM results on a real data Gibbs results from the simulation
Floeter, Sergio Ricardo
1 REGIMENTO DO MESTRADO PROFISSIONAL EM AGROECOSSISTEMAS1 REGIMENTO DO CURSO DE MESTRADO Curso de Mestrado Profissional conduz ao grau de Mestre Profissional em Agroecossistemas. Art. 2º Curso e constam de resolução desse órgão. Sendo dinâmicas, áreas de concentração e linhas de pesquisa
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, REA DE CONCENTRAO EM
REGIMENTO DO CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, ÁREA DE CONCENTRAÇÂO EM COMBUSTÃO E PROPULSÃO TÍTULO IV DO CORPO DOCENTE Art. 7o O Corpo Docente do Curso é constituído por. Parágrafo 1o Poderão fazer parte do Corpo Docente do Curso, como professores colaboradores, docentes de
R. L. Collins
2007-03-04
Consider the electric field E about an electron. Its source has been thought a substance called charge, enclosed within a small volume that defines the size of the electron. Scattering experiments find no size at all. Charge is useful, but mysterious. This study concludes that charge is not real. Useful, but not real. Absent real charge, the electric field must look to a different source. We know another electric field, vxB, not sourced by charge. A simple model of the electron, using EM fields only, has been found that generates an electric field vxB very like E. Gauss' law finds the model contains charge, but div vxB cannot find the charge density. The model contains a permanent magnetic flux quantum, configured as a dipole. The dipolar B fields spin around the symmetry axis, accounting for angular momentum. Spin stabilizes the magnetic flux quantum, and creates the vxB electric field. Stability in this model is dynamic. Energy is exchanged between the dipolar magnetic moment and an encircling toroidal displacement current, at the Compton frequency, mc^2/h = 1.24x10^20 Hz. The electric field undulates at this rate, instead of being static like E associated with charge. Absent any real charge, we have to abandon the notion that size of a charged particle is that of a small sack full of charge. The only electric field is vxB, and its source is not charge. What is the size of an electron? Coulomb scattering finds it point-like, but its spinning B fields extend to infinity.
EMS adaptation for climate change
NASA Astrophysics Data System (ADS)
Pan, C.; Chang, Y.; Wen, J.; Tsai, M.
2010-12-01
The purpose of this study was to find an appropriate scenario of pre-hospital transportation of an emergency medical service (EMS) system for burdensome casualties resulting from extreme climate events. A case of natural catastrophic events in Taiwan, 88 wind-caused disasters, was reviewed and analyzed. A sequential-conveyance method was designed to shorten the casualty transportation time and to promote the efficiency of ambulance services. A proposed mobile emergency medical center was first constructed in a safe area, but nearby the disaster area. The Center consists of professional medical personnel who process the triage of incoming patients and take care of casualties with minor injuries. Ambulances in the Center were ready to sequentially convey the casualties with severer conditions to an assigned hospital that is distant from the disaster area for further treatment. The study suggests that if we could construct a spacious and well-equipped mobile emergency medical center, only a small portion of casualties would need to be transferred to distant hospitals. This would reduce the over-crowding problem in hospital ERs. First-line ambulances only reciprocated between the mobile emergency medical center and the disaster area, saving time and shortening the working distances. Second-line ambulances were highly regulated between the mobile emergency medical center and requested hospitals. The ambulance service of the sequential-conveyance method was found to be more efficient than the conventional method and was concluded to be more profitable and reasonable on paper in adapting to climate change. Therefore, additional practical work should be launched to collect more precise quantitative data.
NASA Astrophysics Data System (ADS)
Shech, Elay
2015-04-01
This paper looks at the nature of idealizations and representational structures appealed to in the context of the fractional quantum Hall effect, specifically, with respect to the emergence of anyons and fractional statistics. Drawing on an analogy with the Aharonov-Bohm effect, it is suggested that the standard approach to the effects—(what we may call) the topological approach to fractional statistics—relies essentially on problematic idealizations that need to be revised in order for the theory to be explanatory. An alternative geometric approach is outlined and endorsed. Roles for idealizations in science, as well as consequences for the debate revolving around so-called essential idealizations, are discussed.
Berry's phase in rotating systems
NASA Astrophysics Data System (ADS)
Cui, Shi-Min; Xu, Hong-Hua
1991-09-01
It is shown that, in addition to the Aharonov-Bohm-like phase studied previously [M. V. Berry, Proc. R. Soc. London Ser. A 392, 45 (1984); Y. Aharakov and J. Anandan, Phys. Rev. Lett. 58, 1593 (1987); C. H. Tsai and D. Neilson, Phys. Rev. A 37, 619 (1988)], Berry's topological phase also appears for purely mechanical reasons in systems rotating at slowly-time-varying angular velocity about a fixed center. A possible experiment to probe this manifestation of Berry's phase is discussed.
Transverse electric field in a mesoscopic Luttinger-liquid ring
NASA Astrophysics Data System (ADS)
Šimánek, E.
1999-08-01
The electric field within a ring containing repulsively interacting electrons is estimated using the spinless Luttinger-liquid model extended to allow transverse excitations due to the radial centrifugal force. The radial voltage drop across a ring, threaded by the Aharonov-Bohm flux, consists of a flux-periodic part that is independent of the interaction, and a flux-independent part that is proportional to the square root of the inverse compressibility of the electron gas. The voltage drop obtained from perturbation theory is consistent with Bernoulli's equation.
How to Measure Magnetic Flux with a Single Position Measurement?
Yakir Aharonov; Eliahu Cohen
2014-08-29
Current methods for measuring magnetic flux are based on performing many measurements over a large ensemble of electrons. We propose a novel method for measuring the flux modulo hc/e using only a single electron. Furthermore, we show, for the first time, how to understand this result on geometric grounds when utilizing only the quantization of angular momentum. A transformation to a rotating frame of reference reveals the nonlocal effect of magnetic flux on the electron, without the need of solving the Schrodinger equation. This provides a new intuition for understanding the Aharonov-Bohm (AB) effect.
NASA Astrophysics Data System (ADS)
Sameer, M. Ikhdair; Majid, Hamzavi
2012-11-01
We study the effects of the perpendicular magnetic and Aharonov—Bohm (AB) flux fields on the energy levels of a two-dimensional (2D) Klein—Gordon (KG) particle subjected to an equal scalar and vector pseudo-harmonic oscillator (PHO). We calculate the exact energy eigenvalues and normalized wave functions in terms of chemical potential parameter, magnetic field strength, AB flux field, and magnetic quantum number by means of the Nikiforov—Uvarov (NU) method. The non-relativistic limit, PHO, and harmonic oscillator solutions in the existence and absence of external fields are also obtained.
NASA Astrophysics Data System (ADS)
Pala, M. G.; Baltazar, S.; Martins, F.; Hackens, B.; Sellier, H.; Ouisse, T.; Bayot, V.; Huant, S.
2009-07-01
We study scanning gate microscopy (SGM) in open quantum rings obtained from buried semiconductor InGaAs/InAlAs heterostructures. By performing a theoretical analysis based on the Keldysh-Green function approach we interpret the radial fringes observed in experiments as the effect of randomly distributed charged defects. We associate SGM conductance images with the local density of states (LDOS) of the system. We show that such an association cannot be made with the current density distribution. By varying an external magnetic field we are able to reproduce recursive quasi-classical orbits in LDOS and conductance images, which bear the same periodicity as the Aharonov-Bohm effect.
Spin wave interaction with topological defects.
Turski, L A; Mi?kowski, M
2009-09-16
Following our earlier gauge field theory analysis of the diffusion and interactions of classical and quantum waves with topological defects in solids (screw and edge dislocations), we present the analysis of the interaction of a classical spin wave with a screw dislocation studied within the Heisenberg ferromagnet model in which spins are located on a lattice containing dislocations. We show that the spin wave interaction with the screw dislocation shows a similarity to the Aharonov-Bohm-like deflection found previously for scattering of acoustic waves on the same type of defects. PMID:21832357
Cloaking two-dimensional fermions
Lin, De-Hone [Department of Physics, National Sun Yat-sen University, Kaohsiung, Taiwan (China)
2011-09-15
A cloaking theory for a two-dimensional spin-(1/2) fermion is proposed. It is shown that the spinor of the two-dimensional fermion can be cloaked perfectly through controlling the fermion's energy and mass in a specific manner moving in an effective vector potential inside a cloaking shell. Different from the cloaking of three-dimensional fermions, the scaling function that determines the invisible region is uniquely determined by a nonlinear equation. It is also shown that the efficiency of the cloaking shell is unaltered under the Aharonov-Bohm effect.
Dirac oscillator interacting with a topological defect
Carvalho, J.; Furtado, C.; Moraes, F. [Unidade Academica de Tecnologia de Alimentos, CCTA, Universidade Federal de Campina Grande, Pereiros, 58840-000, Pombal, Paraiba (Brazil); Departamento de Fisica, CCEN, Universidade Federal da Paraiba, Cidade Universitaria, 58051-970 Joao Pessoa, Paraiba (Brazil)
2011-09-15
In this work we study the interaction problem of a Dirac oscillator with gravitational fields produced by topological defects. The energy levels of the relativistic oscillator in the cosmic string and in the cosmic dislocation space-times are sensible to curvature and torsion associated to these defects and are important evidence of the influence of the topology on this system. In the presence of a localized magnetic field the energy levels acquire a term associated with the Aharonov-Bohm effect. We obtain the eigenfunctions and eigenvalues and see that in the nonrelativistic limit some results known in standard quantum mechanics are reached.
Double-donor complex in vertically coupled quantum dots in a threading magnetic field
2012-01-01
We consider a model of hydrogen-like artificial molecule formed by two vertically coupled quantum dots in the shape of axially symmetrical thin layers with on-axis single donor impurity in each of them and with the magnetic field directed along the symmetry axis. We present numerical results for energies of some low-lying levels as functions of the magnetic field applied along the symmetry axis for different quantum dot heights, radii, and separations between them. The evolution of the Aharonov-Bohm oscillations of the energy levels with the increase of the separation between dots is analyzed. PMID:23013550
Manifestions of Berry's topological phase for the photon
NASA Astrophysics Data System (ADS)
Chiao, R. Y.; Wu, Y.-S.
1986-08-01
Recently, Berry (1984) recognized in quantum mechanics a topological phase factor arising from the adiabatic transport of a system around a closed circuit, which is essentially the Aharonov-Bohm effect in parameter space. Here manifestations of this phase factor are considered for a photon in a state of adiabatically invariant helicity. An interferometer is suggested to see this phase. Also, an effective optical activity for a helical optical fiber is predicted. These effects emerge on a classical level as topological features of Maxwell's theory.
An AB effect without closing a loop
Retzker, A; Botero, A; Nussinov, S; Reznik, B
2005-01-01
We discuss the consequences of the Aharonov-Bohm effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bi-partite or multi-partite entangled photons states, or alternatively, gives rise to an overall AB phase that can be measured relative to another reference system. These setups involve processes of annihilation or creation of electron/hole pairs. We discuss the relevance of such effects in "vacuum Birefringence" in QED, and comment on their connection to other known effects.
Remarks on Aharanov-Bohm effect and geometric phase
Tiwari, S C
2004-01-01
Recently the physical mechanism for geometric phase in optics has been elucidated in terms of the angular momentum holonomy proposed in 1992. Aharonov and Kaufherr (PRL, 92, 070404, 2004) revisit the Aharonov-Bohm effect, and propose non-local exchange of a conserved, gauge invariant quantity that changes the modular momentum of the particle that is responsible for the AB phase shift. We suggest that the net angular momentum shifts proposed for GP may be analogous to the shift in the modulus momentum for the AB effect. At a single photon or electron level such non-trivial, geometric effects seem to hint at a new physics.
Slow wave atom interferometers for rotation sensing
NASA Astrophysics Data System (ADS)
Özcan, Meriç
2007-02-01
A gyroscope based on Sagnac interferometer measures the rotation rate relative to an inertial frame of reference. Sagnac effect originally has been derived and experimentally demonstrated with optical waves. Later, matter wave based Sagnac interferometers were developed due to inherent sensitivity over a photon based system. However in any interferometer whether it is photon or matter wave based the resultant phase shift due to counter-rotating waves is independent of the wave velocity. Here we show that one can have a larger phase shift with slower matter waves using Aharonov-Bohm effect: the phase difference of the counter propagating waves is proportional to the inverse square of the particle velocity.
Topological Properties of Linear Circuit Lattices
NASA Astrophysics Data System (ADS)
Albert, Victor V.; Glazman, Leonid I.; Jiang, Liang
2015-05-01
Motivated by the topologically insulating circuit of capacitors and inductors proposed and tested by Jia et al. [arXiv:1309.0878], we present a related circuit with fewer elements per site. The normal mode frequency matrix of our circuit is unitarily equivalent to the hopping matrix of a quantum spin Hall insulator, and we identify perturbations that do not backscatter the circuit's edge modes. The idea behind these models is generalized, providing a platform to simulate tunable and locally accessible lattices with arbitrary complex spin-dependent hopping of any range. A simulation of a non-Abelian Aharonov-Bohm effect using such linear circuit designs is discussed.
The Nonlocal Pancharatnam Phase in Two-Photon Interferometry
Poonam Mehta; Joseph Samuel; Supurna Sinha
2010-09-03
We propose a polarised intensity interferometry experiment, which measures the nonlocal Pancharatnam phase acquired by a pair of Hanbury Brown-Twiss photons. The setup involves two polarised thermal sources illuminating two polarised detectors. Varying the relative polarisation angle of the detectors introduces a two photon geometric phase. Local measurements at either detector do not reveal the effects of the phase, which is an optical analog of the multiparticle Aharonov-Bohm effect. The geometric phase sheds light on the three slit experiment and suggests ways of tuning entanglement.
Electromagnetic vacuum fluctuations and electron coherence
NASA Astrophysics Data System (ADS)
Ford, L. H.
1993-06-01
The coupling of the quantized electromagnetic field to coherent electrons is investigated. The effects both of photon emission and of the electromagnetic vacuum fluctuations upon electron interference are analyzed. The modifications of the vacuum fluctuations due to a conducting plate lead to a decrease in the amplitude of the interference oscillations. The possibility of observing this effect is discussed. It is also shown that there is an analogue of the Aharonov-Bohm effect in which electron interference is sensitive to vacuum fluctutations in regions from which the electrons are excluded.
REVIEWS OF TOPICAL PROBLEMS: Basic quantum mechanical concepts from the operational viewpoint
NASA Astrophysics Data System (ADS)
Klyshko, D. N.
1998-09-01
The physical meaning of the basic quantum mechanical concepts (such as the wave function, reduction, state preparation and measurement, the projection postulate, and the uncertainty principle) is clarified using realistic experimental procedures and employing classical analogies whenever possible. Photon polarization measurement and particle coordinate and momentum measurement are considered as examples, as also are Einstein-Podolsky-Rosen correlations, Aharonov-Bohm effects, quantum teleportation, etc. Various nonclassicality criteria of quantum models, including photon antibunching and the violation of the Bell inequality, are discussed.
Time-dependent resonant tunnelling for parallel-coupled double quantum dots
NASA Astrophysics Data System (ADS)
Dong, Bing; Djuric, Ivana; Cui, H. L.; Lei, X. L.
2004-06-01
We derive the quantum rate equations for an Aharonov-Bohm interferometer with two vertically coupled quantum dots embedded in each of two arms by means of the nonequilibrium Green function in the sequential tunnelling regime. Based on these equations, we investigate time-dependent resonant tunnelling under a small amplitude irradiation and find that the resonant photon-assisted tunnelling peaks in photocurrent demonstrate a combination behaviour of Fano and Lorentzian resonances due to the interference effect between the two pathways in this parallel configuration, which is controllable by threading the magnetic flux inside this device.
Photons as quasi-charged particles
K. -P. Marzlin; Juergen Appel; A. I. Lvovsky
2007-10-16
The Schrodinger motion of a charged quantum particle in an electromagnetic potential can be simulated by the paraxial dynamics of photons propagating through a spatially inhomogeneous medium. The inhomogeneity induces geometric effects that generate an artificial vector potential to which signal photons are coupled. This phenomenon can be implemented with slow light propagating through an a gas of double-Lambda atoms in an electromagnetically-induced transparency setting with spatially varied control fields. It can lead to a reduced dispersion of signal photons and a topological phase shift of Aharonov-Bohm type.
Remarks on Aharanov-Bohm effect and geometric phase
S C Tiwari
2004-05-14
Recently the physical mechanism for geometric phase in optics has been elucidated in terms of the angular momentum holonomy proposed in 1992. Aharonov and Kaufherr (PRL, 92, 070404, 2004) revisit the Aharonov-Bohm effect, and propose non-local exchange of a conserved, gauge invariant quantity that changes the modular momentum of the particle that is responsible for the AB phase shift. We suggest that the net angular momentum shifts proposed for GP may be analogous to the shift in the modulus momentum for the AB effect. At a single photon or electron level such non-trivial, geometric effects seem to hint at a new physics.
Photons as quasicharged particles
NASA Astrophysics Data System (ADS)
Marzlin, K.-P.; Appel, Jürgen; Lvovsky, A. I.
2008-04-01
The Schrödinger motion of a charged quantum particle in an electromagnetic potential can be simulated by the paraxial dynamics of photons propagating through a spatially inhomogeneous medium. The inhomogeneity induces geometric effects that generate an artificial vector potential to which signal photons are coupled. This phenomenon can be implemented with slow light propagating through a gas of double- ? atoms in an electromagnetically induced transparency setting with spatially varied control fields. It can lead to a reduced dispersion of signal photons and a topological phase shift of Aharonov-Bohm type.
An AB effect without closing a loop
A. Retzker; Y. Aharonov; A. Botero; S. Nussinov; B. Reznik
2006-04-02
We discuss the consequences of the Aharonov-Bohm effect in setups involving several charged particles, wherein none of the charged particles encloses a closed loop around the magnetic flux. We show that in such setups, the AB phase is encoded either in the relative phase of a bi-partite or multi-partite entangled photons states, or alternatively, gives rise to an overall AB phase that can be measured relative to another reference system. These setups involve processes of annihilation or creation of electron/hole pairs. We discuss the relevance of such effects in "vacuum Birefringence" in QED, and comment on their connection to other known effects.
Gauge Field Optics with Anisotropic Media
NASA Astrophysics Data System (ADS)
Liu, Fu; Li, Jensen
2015-03-01
By considering gauge transformations on the macroscopic Maxwell's equations, a two-dimensional gauge field, with its pseudomagnetic field in the real space, is identified as tilted anisotropy in the constitutive parameters. We show that the optical spin Hall effect with broadband response and one-way edge states become possible simply by using anisotropic media. The proposed gauge field also allows us to obtain unidirectional propagation for a particular pseudospin based on the Aharonov-Bohm effect. Our approach will be useful in spoof magneto-optics with arbitrary magnetic fields mimicked by metamaterials with subwavelength unit cells. It also serves as a generic way to design polarization-dependent devices.
Single molecular shuttle-junction: Shot noise and decoherence
NASA Astrophysics Data System (ADS)
Lai, Wenxi; Zhang, Chao; Ma, Zhongshui
2015-02-01
Single molecular shuttle-junction is one kind of nanoscale electromechanical tunneling system. In this junction, a molecular island oscillates depending on its charge occupation, and this charge dependent oscillation leads to modulation of electron tunneling through the molecular island. This paper reviews recent development on the study of current, shot noise and decoherence of electrons in the single molecular shuttle-junction. We will give detailed discussion on this topic using the typical system model, the theory of fully quantum master equation and the Aharonov-Bohm interferometer.
Single molecular shuttle-junction: Shot noise and decoherence
NASA Astrophysics Data System (ADS)
Lai, Wenxi; Zhang, Chao; Ma, Zhongshui
2014-09-01
Single molecular shuttle-junction is one kind of nanoscale electromechanical tunneling system. In this junction, a molecular island oscillates depending on its charge occupation, and this charge dependent oscillation leads to modulation of electron tunneling through the molecular island. This paper reviews recent development on the study of current, shot noise and decoherence of electrons in the single molecular shuttle-junction. We will give detail discussions on this topic using the typical system model, the theory of fully quantum master equation and the Aharonov-Bohm interferometer.
Electromagnetic potential vectors and the Lagrangian of a charged particle
NASA Technical Reports Server (NTRS)
Shebalin, John V.
1992-01-01
Maxwell's equations can be shown to imply the existence of two independent three-dimensional potential vectors. A comparison between the potential vectors and the electric and magnetic field vectors, using a spatial Fourier transformation, reveals six independent potential components but only four independent electromagnetic field components for each mode. Although the electromagnetic fields determined by Maxwell's equations give a complete description of all possible classical electromagnetic phenomena, potential vectors contains more information and allow for a description of such quantum mechanical phenomena as the Aharonov-Bohm effect. A new result is that a charged particle Lagrangian written in terms of potential vectors automatically contains a 'spontaneous symmetry breaking' potential.
Cold Atoms in Non-Abelian Gauge Potentials: From the Hofstadter Moth to Lattice Gauge Theory
Osterloh, K. [Institut fuer Theoretische Physik, Universitaet Hannover, D-30167 Hannover (Germany); Baig, M. [IFAE, Universitat Autonoma de Barcelona, 08193 Bellaterra, Barcelona (Spain); Santos, L. [Institut fuer Theoretische Physik III, Universitaet Stuttgart, D-70550 Stuttgart (Germany); Zoller, P. [Institute for Theoretical Physics, University of Innsbruck, A-6020 Innsbruck (Austria); Lewenstein, M. [Institut fuer Theoretische Physik, Universitaet Hannover, D-30167 Hannover (Germany); ICFO-Institut de Ciencies Fotoniques, 08034 Barcelona (Spain)
2005-07-01
We demonstrate how to create artificial external non-Abelian gauge potentials acting on cold atoms in optical lattices. The method employs atoms with k internal states, and laser assisted state sensitive tunneling, described by unitary kxk matrices. The single-particle dynamics in the case of intense U(2) vector potentials lead to a generalized Hofstadter butterfly spectrum which shows a complex mothlike structure. We discuss the possibility to realize non-Abelian interferometry (Aharonov-Bohm effect) and to study many-body dynamics of ultracold matter in external lattice gauge fields.
A General Method for Deriving Vector Potentials Produced by Knotted Solenoids
V. V. Sreedhar
2015-01-06
A general method for deriving exact expressions for vector potentials produced by arbitrarily knotted solenoids is presented. It consists of using simple physics ideas from magnetostatics to evaluate the magnetic field in a surrogate problem. The latter is obtained by modelling the knot with wire segments carrying steady currents on a cubical lattice. The expressions for a 31 (trefoil) and a 41 (figure-eight) knot are explicitly worked out. The results are of some importance in the study of the Aharonov-Bohm effect generalised to a situation in which charged particles moving through force-free regions are scattered by fluxes confined to the interior of knotted impenetrable tubes.
Quasiballistic transport of Dirac fermions in a Bi2Se3 nanowire.
Dufouleur, J; Veyrat, L; Teichgräber, A; Neuhaus, S; Nowka, C; Hampel, S; Cayssol, J; Schumann, J; Eichler, B; Schmidt, O G; Büchner, B; Giraud, R
2013-05-01
Quantum coherent transport of surface states in a mesoscopic nanowire of the three-dimensional topological insulator Bi(2}Se(3) is studied in the weak-disorder limit. At very low temperatures, many harmonics are evidenced in the Fourier transform of Aharonov-Bohm oscillations, revealing the long phase coherence length of spin-chiral Dirac fermions. Remarkably, from their exponential temperature dependence, we infer an unusual 1/T power law for the phase coherence length L(?)(T). This decoherence is typical for quasiballistic fermions weakly coupled to their environment. PMID:23683235
Pure phase decoherence in a ring geometry
Zhu, Z. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Aharony, A.; Entin-Wohlman, O. [Department of Physics and the Ilse Katz Center for Meso- and Nano-Scale Science and Technology, Ben Gurion University, Beer Sheva 84105 (Israel); Pacific Institute of Theoretical Physics, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Stamp, P. C. E. [Department of Physics and Astronomy, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada); Pacific Institute of Theoretical Physics, University of British Columbia, 6224 Agricultural Rd., Vancouver, British Columbia, V6T 1Z1 (Canada)
2010-06-15
We study the dynamics of pure phase decoherence for a particle hopping around an N-site ring, coupled both to a spin bath and to an Aharonov-Bohm flux which threads the ring. Analytic results are found for the dynamics of the influence functional and of the reduced density matrix of the particle, both for initial single wave-packet states, and for states split initially into two separate wave packets moving at different velocities. We also give results for the dynamics of the current as a function of time.
Filter banks and the EM algorithm
Mair, B.A.; Carroll, R.B.; Anderson, J.M.M. [Univ. of Florida, Gainesville, FL (United States)
1996-12-31
In this paper, we present a wavelet based modification of the ML-EM algorithm for reconstructing positron emission tomography images. By using the filter bank implementation of the wavelet transform, this algorithm has the flexibility to incorporate a priori information, while maintaining the same computational complexity as the standard ML-EM algorithm. Thus, it has a significant computational advantage over usual Bayesian methods. It differs from recent wavelet-based Bayesian methods as it achieves {open_quotes}regularization{close_quotes} by an adaptive, wavelet-based method of thresholding which minimizes Stein`s Unbiased Estimate of Risk. The basic method consists of applying Donoho and Johnstone`s SureShrink wavelet denoising of the Poisson data, and then applying the standard ML-EM algorithm to the denoised data. A more elaborate method is discussed in which a wavelet denoising step is inserted after each EM iteration. This technique differs from previous smoothing techniques applied to the ML-EM algorithm since it is able to recover edges in discontinuous images.
Risk Communication Within the EM Program
Edelson, M.
2003-02-26
The U.S. Department of Energy Environmental Management program (EM) conducts the most extensive environmental remediation effort in the world. The annual EM budgets have exceeded $6,000,000,000 for approximately ten years and EM has assumed responsibility for the cleanup of the largest DOE reservations (i.e., at Hanford, Washington, Aiken, South Carolina, and Idaho Falls, Idaho) as well as the facilities at Rocky Flats, Colorado and in Ohio. Each of these sites has areas of extensive radioactive and chemical contamination, numerous surplus facilities that require decontamination and removal, while some have special nuclear material that requires secure storage. The EM program has been criticized for being ineffective (1) and has been repeatedly reorganized to address perceived shortcomings. The most recent reorganization was announced in 2001 to become effective at the beginning of the 2003 Federal Fiscal Year (i.e., October 2002). It was preceded by a ''top to bottom'' review (TTBR) of the program (2) that identified several deficiencies that were to be corrected as a result of the reorganization. One prominent outcome of the TTBR was the identification of ''risk reduction'' as an organizing principle to prioritize the activities of the new EM program. The new program also sought to accelerate progress by identifying a set of critical activities at each site that could be accelerated and result in more rapid site closure, with attendant risk, cost, and schedule benefits. This paper investigates how the new emphasis on risk reduction in the EM program has been communicated to EM stakeholders and regulators. It focuses on the Rocky Flats Environmental Technology Site (RFETS) as a case study and finds that there is little evidence for a new emphasis on risk reduction in EM communications with RFETS stakeholders. Discussions between DOE and RFETS stakeholders often refer to ''risk,'' but the word serves as a placeholder for other concepts. Thus ''risk'' communication at RFETS is lively and involves important issues, but often does not inform participants about true ''risk reduction.''
Simplex EMS users knock company's service support
Cohn, L.
1982-06-14
Simplex Tape Recorder Co. is not responding fast enough to please some of its energy management system (EMS) users who need service or new parts. The users complain that Simplex load-shedding, time-of-day control, and duty-cycling functions do not compare with the quality of its security and fire functions. Company spokesmen claim that service and parts are available on a 24-hour basis from technically-trained personnel. The company has sold time clocks since 1959, and marketed microprocessor-based EMS equipment since 1980. Users and service managers disagree over reported delays. (DCK)
On Convergence Properties of the EM Algorithm for Gaussian Mixtures
Jordan, Michael
1995-04-21
"Expectation-Maximization'' (EM) algorithm and gradient-based approaches for maximum likelihood learning of finite Gaussian mixtures. We show that the EM step in parameter space is obtained from the gradient via a ...
CURSO DE PS-GRADUAO EM COMPUTAO APLICADA
CURSO DE PÓS-GRADUAÇÃO EM COMPUTAÇÃO APLICADA Coordenador Acadêmico Reinaldo Roberto Rosa, Dr, participação em todos os WORCAPs (Workshop dos Cursos de Mestrado e Doutorado da CAP) e, obrigatoriedade de
EM-ONE : an architecture for reflective commonsense thinking
Singh, Pushpinder, 1972-2006.
2005-01-01
This thesis describes EM-ONE, an architecture for commonsense thinking capable of reflective reasoning about situations involving physical, social, and mental dimensions. EM-ONE uses as its knowledge base a library of ...
UNIVERSIDADE DE BRASLIA CENTRO DE EXCELNCIA EM TURISMO -CET
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA CENTRO DE EXCELÃ?NCIA EM TURISMO - CET PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM TURISMO EDITAL No. 01/2013 UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM TURISMO EDITAL No. 01/2013 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S- GRADUAÃ?Ã?O EM TURISMO PARA OS CURSOS DE MESTRADO
UNIVERSIDADE DE BRASLIA CENTRO DE EXCELNCIA EM TURISMO -CET
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA CENTRO DE EXCELÃ?NCIA EM TURISMO - CET PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM TURISMO EDITAL No. 04/2013 1 UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM TURISMO EDITAL No. 04/2012 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM TURISMO PARA OS CURSOS DE MESTRADO
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ECOLOGIA
Lucero, Jorge Carlos
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA EDITAL No. 01/2012 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA PARA O CURSO DE DOUTORADO PARA O SEGUNDO PERÍODO LETIVO DE 2012 1. PREÂMBULO 1.1 A Coordenadora do Programa de Pós-Graduação em ECOLOGIA, no uso de suas
Pesquisa em Memria ltima alterao: 10 de Outubro de 2006
Chaimowicz, Luiz
Pesquisa em Memória Secundária Última alteração: 10 de Outubro de 2006 Transparências elaboradas, Leonardo Mata #12;Projeto de Algoritmos Cap.1 Introdução 1 Introdução · Pesquisa em memória secundária transferências). · Memórias secundárias: apenas um registro pode ser acessado em um dado momento (acesso
7 CFR 1945.35 - Special EM loan training.
Code of Federal Regulations, 2012 CFR
2012-01-01
...2012-01-01 2012-01-01 false Special EM loan training. 1945.35 Section 1945...Assistance-General § 1945.35 Special EM loan training. (a) General...completed they will be well qualified to process EM loans without undue delay. The...
Online EM Algorithm for Hidden Markov Models Olivier Cappe
Online EM Algorithm for Hidden Markov Models Olivier CappÂ´e LTCI, TELECOM ParisTech & CNRS Abstract recursive) version of the Expectation-Maximization (EM) algorithm. It is first shown that under suitable mixing assumptions, the large sample behavior of the traditional (batch) EM algorithm may be analyzed
7 CFR 759.6 - EM to be made available.
Code of Federal Regulations, 2014 CFR
2014-01-01
... 2014-01-01 2014-01-01 false EM to be made available. 759.6 Section 759...DESIGNATIONS AND NOTIFICATIONS § 759.6 EM to be made available. (a) For purposes of the EM Program under part 764, subpart I, of...
On Convergence Properties of the EM Algorithm for Gaussian Mixtures
Lei Xu; Michael I. Jordan
1996-01-01
We build up the mathematical connection between the Expectation-Maximization (EM) algorithm and gradient-based approaches for maximum likelihood learning of finite gaussian mixtures. We show that the EM step in parameter space is obtained from the gradient via a projection matrix P, and we provide an explicit expression for the matrix. We then analyze the convergence of EM in terms of
COMBINATION OF EM AND DC MEASUREMENTS FOR UPPER CRUSTAL STUDIES
Harinarayana, T.
COMBINATION OF EM AND DC MEASUREMENTS FOR UPPER CRUSTAL STUDIES T. HARINARAYANA National geophysical methods, electrical (E) and electromagnetic (EM) methods also suffer from ambiguity benefit of obtaining more confidence in the derived model, joint use of E and EM methods has added
Em dvida o valor de cortes a devolver s universidades
Instituto de Sistemas e Robotica
Em dúvida o valor de cortes a devolver às universidades Secretário de Estado reuniu-se ontem com o a garantia de que "a muito curto prazo" se- rão entregues os 30 milhões em dívida, revelou ao JN o rei- tor verbas cortadas que são entregues em valores inferiores". "Nos próximos dias, tenho de tomar decisões
EM Effects on Semiconductor Devices, Gates and Integrated Circuit
Anlage, Steven
EM Effects on Semiconductor Devices, Gates and Integrated Circuit Interconnects Dept. of Electrical Xi Shao, Parvez N. Guzdar Akin Akturk, Zeynep Dilli, Bo Yang, Todd Firestone #12;EM Effects Verify with experiments: Chips fabricated through MOSIS #12;Outline EM Coupling: Levels Investigated Task
Galp investe em cincia no Brasil Margarida Davim
Instituto de Sistemas e Robotica
Galp investe em ciência no Brasil Margarida Davim margarida.davim@sol.pt Lei brasileira obriga petrolíferas a investir 1% dos lucros em investigação. Até 2017, Galp deve apoiar projectos no valor de 140 dólares em investiga- ção e projectos científicos no Brasil até 2017. O investimento - cerca de 102
Online EM for Unsupervised Models Percy Liang Dan Klein
Pratt, Vaughan
Online EM for Unsupervised Models Percy Liang Dan Klein Computer Science Division, EECS Department) EM algorithm plays an important role in unsupervised induction, but it some- times suffers from slow find bet- ter solutions than those found by batch EM. We support these findings on four unsuper- vised
Ps-Graduao em Gerenciamento de Sistemas Espaciais Disciplina Isolada
Pós-Graduação em Gerenciamento de Sistemas Espaciais Disciplina Isolada Documentos a serem apresentados na secretaria do CSE: comprovante de: matricula do candidato em Curso de Pós-Graduação ou de ser Substituído por Declaração que conste data de colação de grau. Em hipótese alguma será aceito aluno que não
Online EM Algorithm for Hidden Markov Models Olivier Cappe
Paris-Sud XI, Université de
Online EM Algorithm for Hidden Markov Models Olivier Capp´e LTCI, Telecom ParisTech & CNRS Abstract in the Expectation-Maximization (EM) methodology consists in reparameterizing the problem using complete in HMMs based on an auxiliary recursion. Although the proposed online EM algorithm resembles a classical
EM Effects on Semiconductor Devices Gates and Integrated Circuit
Anlage, Steven
EM Effects on Semiconductor Devices Gates and Integrated Circuit Interconnects Dept. of Electrical Xi Shao, Parvez N. Guzdar4 Akin Akturk, Zeynep Dilli, Yun Bai, Todd Firestone #12;EM Effects. Verify with experiments: Chips fabricated through MOSIS #12;Outline EM Coupling: Levels Investigated Task
Parallel EM Learning for Symbolic-Statistical Models
Sato, Taisuke
Parallel EM Learning for Symbolic- Statistical Models Yusuke Izumi Department of Computer Science as previous author) sato@mi.cs.titech.ac.jp keywords: parallel EM algorithm, symbolic-statistical models, PRISM, distributed parallel computing Summary EM learning, i.e. parameter learning for probabilistic
7 CFR 1945.35 - Special EM loan training.
Code of Federal Regulations, 2011 CFR
2011-01-01
...2011-01-01 2009-01-01 true Special EM loan training. 1945.35 Section 1945...Assistance-General § 1945.35 Special EM loan training. (a) General...completed they will be well qualified to process EM loans without undue delay. The...
EM DESTAQUE Resgate do Chipre empurra bolsas para o vermelho
Instituto de Sistemas e Robotica
EM DESTAQUE Resgate do Chipre empurra bolsas para o vermelho Resgate da União Europeia ao Chipre: Interessados em inve têm de se preparar - Câmara de co Moçambique: Portugueses que pro de Comércio triplicou em dois anos Outros sites Impresa: SIC TV Mais Escape Olhares J. Letras V. Júnior E. Informática
7 CFR 759.6 - EM to be made available.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 2013-01-01 2013-01-01 false EM to be made available. 759.6 Section 759...DESIGNATIONS AND NOTIFICATIONS § 759.6 EM to be made available. (a) For purposes of the EM Program under part 764, subpart I, of...
7 CFR 1945.35 - Special EM loan training.
Code of Federal Regulations, 2010 CFR
2010-01-01
...2010-01-01 2009-01-01 true Special EM loan training. 1945.35 Section 1945...Assistance-General § 1945.35 Special EM loan training. (a) General...completed they will be well qualified to process EM loans without undue delay. The...
Electromagnetic ``Bubbles'' and Shock Waves: Unipolar, Nonoscillating EM Solitons
A. E. Kaplan; P. L. Shkolnikov
1995-01-01
We show that atomic gases can support solitary pulses of a unipolar electromagnetic field (``EM bubbles'') with amplitude up to the atomic field ( ~109 V\\/cm) and duration down to ~ 10-16 s. EM bubbles propagate without dispersion, are stable, and are insensitive to the change of gas density. Atomic gasses can also support an EM shock wave forming a
ISSN 0103-9741 Monografias em Cincia da Computao
Endler, Markus
Sistema de recomendação: uma abordagem por ltro colaborativo baseado em modelos 1 Dárlinton Barbosa FeresPUC ISSN 0103-9741 Monografias em Ciência da Computação n 19/10 Sistemas de Recomendação: uma abordagem por filtro colaborativo baseado em modelos Dárlinton Barbosa Feres Carvalho Ruy Luiz Milidiú
Marvin, robô construtor para competição em robótica móvel
André Martin Narciso; Carlos Augusto; Bentes da Silva; Jackson Paul Matsuura
renatohsp@gmail .com Resumo: Este artigo é sobre a construção do robô autônomo Marvin o Construtor, que foi construído para participar da IV Competição IEEE Brasileira de Robô. A tarefa consiste em empilhar blocos em uma área predeterminada em um menor tempo possível, ganha a torre mais alta. O robô, construído por alunos do Instituto Tecnológico de Aeronáutica (ITA), foi construído
REGIMENTO DO CURSO DE PSGRADUAO EM COMPUTAO APLICADA
REGIMENTO DO CURSO DE PÓSGRADUAÇÃO EM COMPUTAÇÃO APLICADA Regimento aprovado pelo CPG em 19/02/2003. TÍTULO I DOS OBJETIVOS E FINALIDADES Art 1º O Curso de PósGraduação a nível de Mestrado e Doutorado em Computação Aplicada CAP, doravante referido como Curso, objetiva formar e capacitar pessoal de nível
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM COMBUSTÃO E PROPULSÃO Coordenadora Acadêmica do Curso Evandro Marconi Rocco Coordenador da Área de Concentração David, Doutor, INPE, 2006. #12;CURSO DE ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM COMBUSTÃO E
REGIMENTO DO CURSO DE PSGRADUAO EM COMPUTAO APLICADA
REGIMENTO DO CURSO DE PÓSGRADUAÇÃO EM COMPUTAÇÃO APLICADA Regimento aprovado pelo CPG em 04/11/2004. TÍTULO I DOS OBJETIVOS E FINALIDADES Art 1º O Curso de PósGraduação a nível de Mestrado e Doutorado em Computação Aplicada CAP, doravante referido como Curso, objetiva formar e capacitar pessoal de nível
Incentives for P2P-Assisted Content Distribution: If You Can't Beat 'Em, Join 'Em
Wierman, Adam
Incentives for P2P-Assisted Content Distribution: If You Can't Beat 'Em, Join 'Em Vinod Ramaswamy distributors to search for methods of defraying costs. One technique that is often suggested for defraying
Novo modelo em 2015 para financiar
Instituto de Sistemas e Robotica
não tem sido cabal- mente aplicada. O que o Governo propõe agora é "criar um modelo de financiamento Governo vai agora discutir com as universidades e politécnicos como pôr a ideia em prática, dos indicadores ao modo como são calculados. "Solicitámos hoje o contributo das instituições. Agora vai começar o
Efficient Scanning for EM Based Target Localization
Fua, Pascal
of the time. 1 Introduction Focused Ion Beam Scanning Electron Microscopes (FIB-SEM) and their ability Image Fig. 1. FIB-SEM Scanning Process. The microscope repeatedly scans the surface of a sample blockEfficient Scanning for EM Based Target Localization Raphael Sznitman, Aurelien Lucchi, Natasa
EM Algorithms for PCA and SPCA
Sam T. Roweis
1997-01-01
Abstract I present an expectation - maximization (EM) algorithm for principal component analysis (PCA) The algorithm allows a few eigenvectors and eigenvalues to be extracted from large collections of high dimensional data It is computationally very efficient in space and time It also natu - rally accommodates missing information I also introduce a new variant of PCA called sensible principal
EM algorithms for ML factor analysis
Donald B. Rubin; Dorothy T. Thayer
1982-01-01
The details of EM algorithms for maximum likelihood factor analysis are presented for both the exploratory and confirmatory models. The algorithm is essentially the same for both cases and involves only simple least squares regression operations; the largest matrix inversion required is for aq ×q symmetric matrix whereq is the matrix of factors. The example that is used demonstrates that
EMS Division Potential Benefits of Selected
Validation Program for ONR 300 KW Test Stand Motor 3.7 MW Motor Operated Successfully with SC magnet at full Homopolar Motors & Projections for Ship Propulsion Topics NOTE: Search for the interplay of technical disciplines!!!!! #12;EMS Division Homopolar Motor Outline ·Homopolar Motor Basics ·Homopolar Motor Technology
Recursos Estratégicos em Propriedades Rurais Familiares
Marcelo Fernandes Pacheco Dias; Eugenio Avila Pedrozo
2008-01-01
A agricultura familiar tem papel importante nos agronegócios. A manutenção desses agricultores é uma das preocupações prioritárias dos governos. Também é amplamente conhecido o fato que o desempenho das propriedades familiares varia significativamente. Esse artigo busca contribuir para a explicação do porquê dessa variação de desempenho, através da Teoria Baseado em Recursos (RBV). Nesse sentido, foi desenvolvido um estudo exploratório
EM Algorithm for Symmetric Causal Independence Models
Rasa Jurgelenaite; Tom Heskes
2006-01-01
Causal independence modelling is a well-known method both for reducing the size of probability tables and for explaining the underly- ing mechanisms in Bayesian networks. In this paper, we present the EM algorithm to learn the parameters in causal independence models based on the symmetric Boolean function. The developed algorithm enables us to assess the practical usefulness of the symmetric
FAGNER LUIZ DA C. FREITAS; ANDRÉ S. ZANETTI; CÉLIO R. MACHADO; ROSANGELA Z. MACHADO
1 ABSTRACT:- FREITAS, F.L. DA C.; ALMEIDA, K. DE S.; ZANETTI, A.S.; NASCIMENTO, A.A. DO; MACHADO, C. R.; MACHADO, R.Z. (Species of the genus Eimeria (Apicomplexa: Eimeriidae) in giant anteaters (Myrmecophaga tridactyla Linnaeus, 1758) in captivity). Espécies do gênero Eimeria (Apicomplexa: Eimeriidae) em Tamanduás-bandeira (Myrmecophaga tridactyla Linnaeus, 1758) em cativeiro. Revista Brasileira de Parasitologia Veterinária, v. 15, n. 1, p.
Information geometry of the EM and em algorithms for neural networks
Shun-ichi Amari
1995-01-01
In order to realize an input-output relation given by noise-contaminated examples,it is effective to use a stochastic model of neural networks. A model networkincludes hidden units whose activation values are not specified nor observed. It isuseful to estimate the hidden variables from the observed or specified input-outputdata based on the stochastic model. Two algorithms, the EM - and em-algorithms,have so
Neuza H. Lopes; Jeane M. Tsutsui; Whady A. Hueb
2007-01-01
RESUMO Diabetes mellitus é um dos principais fatores de risco para a doença arterial coronária. A doença progride de forma mais acelerada em pacientes diabéticos e está associada com pior prognóstico. Embora a revascularização miocárdica garanta alívio rápido dos sintomas em pacientes com doença arterial coronária documentada, não existe substancial evidência de benefício prognóstico, salvo em situações anatômicas específicas. Adicionalmente,
REGIMENTO DO CURSO DE PSGRADUAO EM COMPUTAO APLICADA Regimento aprovado pelo CPG em 07/11/2006
REGIMENTO DO CURSO DE PÓSGRADUAÇÃO EM COMPUTAÇÃO APLICADA Regimento aprovado pelo CPG em 07/11/2006 TÍTULO I DOS OBJETIVOS E FINALIDADES Art 1º O Curso de pósgraduação em Computação Aplicada, doravante referido como Curso, mantém programas de Mestrado e Doutorado com objetivo de formar e capacitar pessoal
Crosshole EM in steel-cased boreholes
Wilt, M.; Lee, K.H.; Becker, A.; Spies, B.; Wang, B.
1996-07-01
The application of crosshole EM methods through steel well-casing was investigated in theoretical, laboratory and field studies. A numerical code was developed that calculates the attenuation and phase delay of an EM dipole signal propagated through a steel well casing lodged in a homogeneous medium. The code was validated with a scale model and used for sensitivity studies of casing and formation properties. Finally, field measurements were made in an oil field undergoing waterflooding. Our most important findings are that (1) crosshole surveys are feasible using a well pair with one metallic and one non-metallic casing. (2) The casing effect seems be localized within the pipe section that includes the sensor. (3) The effects of the casing can be corrected using simple means and (4) crosshole field data that are sensitive to both formation and casing were acquired in a working environment.
Topic-based language models using EM
Daniel Gildea; Thomas Hofmann
1999-01-01
In this paper, we propose a novel statistical language model to capture topic-related long-range dependencies. Topics are mod- eled in a latent variable framework in which we also derive an EM algorithm to perform a topic factor decomposition based on a segmented training corpus. The topic model is combined with a standard language model to be used for on-line word
Telescópio de patrulhamento solar em 12 GHz
NASA Astrophysics Data System (ADS)
Utsumi, F.; Costa, J. E. R.
2003-08-01
O telescópio de patrulhamento solar é um instrumento dedicado à observação de explosões solares com início de suas operações em janeiro de 2002, trabalhando próximo ao pico de emissão do espectro girossincrotrônico (12 GHz). Trata-se de um arranjo de três antenas concebido para a detecção de explosões e determinação em tempo real da localização da região emissora. Porém, desde sua implementação em uma montagem equatorial movimentada por um sistema de rotação constante (15 graus/hora) o rastreio apresentou pequenas variações de velocidade e folgas nas caixas de engrenagens. Assim, tornou-se necessária a construção de um sistema de correção automática do apontamento que era de fundamental importância para os objetivos do projeto. No segundo semestre de 2002 empreendemos uma série de tarefas com o objetivo de automatizar completamente o rastreio, a calibração, a aquisição de dados, controle de ganhos, offsets e transferência dos dados pela internet através de um projeto custeado pela FAPESP. O rastreio automático é realizado através de um inversor que controla a freqüência da rede de alimentação do motor de rastreio podendo fazer micro-correções na direção leste-oeste conforme os radiômetros desta direção detectem uma variação relativa do sinal. Foi adicionado também um motor na direção da declinação para correção automática da variação da direção norte-sul. Após a implementação deste sistema a precisão do rastreio melhorou para um desvio máximo de 30 segundos de arco, o que está muito bom para este projeto. O Telescópio se encontra em funcionamento automático desde março de 2003 e já conta com várias explosões observadas após a conclusão desta fase de automação. Estamos apresentando as explosões mais intensas do período e com as suas respectivas posições no disco solar.
Simplex EMS users knock company's service support
Cohn
1982-01-01
Simplex Tape Recorder Co. is not responding fast enough to please some of its energy management system (EMS) users who need service or new parts. The users complain that Simplex load-shedding, time-of-day control, and duty-cycling functions do not compare with the quality of its security and fire functions. Company spokesmen claim that service and parts are available on a 24-hour
Helicopter EMS: Research Endpoints and Potential Benefits
Thomas, Stephen H.; Arthur, Annette O.
2012-01-01
Patients, EMS systems, and healthcare regions benefit from Helicopter EMS (HEMS) utilization. This article discusses these benefits in terms of specific endpoints utilized in research projects. The endpoint of interest, be it primary, secondary, or surrogate, is important to understand in the deployment of HEMS resources or in planning further HEMS outcomes research. The most important outcomes are those which show potential benefits to the patients, such as functional survival, pain relief, and earlier ALS care. Case reports are also important “outcomes” publications. The benefits of HEMS in the rural setting is the ability to provide timely access to Level I or Level II trauma centers and in nontrauma, interfacility transport of cardiac, stroke, and even sepsis patients. Many HEMS crews have pharmacologic and procedural capabilities that bring a different level of care to a trauma scene or small referring hospital, especially in the rural setting. Regional healthcare and EMS system's benefit from HEMS by their capability to extend the advanced level of care throughout a region, provide a “backup” for areas with limited ALS coverage, minimize transport times, make available direct transport to specialized centers, and offer flexibility of transport in overloaded hospital systems. PMID:22203905
Cyclotron braid group structure for composite fermions.
Jacak, J; Jó?wiak, I; Jacak, L; Wieczorek, K
2010-09-01
Although they describe properties of 2D Hall systems in the fractional quantum regime well, composite fermions suffer from the unexplained character of the localized magnetic field flux-tubes attached to each particle in order to reproduce the Laughlin correlations via Aharonov-Bohm phase shifts. The identification of the cyclotron trajectories of 2D charged particles as accessible classical trajectories within the braid group approach at the magnetic field presence, allows, however, for the avoidance of the construction with fluxes. We introduce cyclotron braid subgroups for charged 2D systems at the fractional Landau-level filling associated in a more natural way with composite fermions without invoking field flux-tubes. The Aharonov-Bohm phase shifts caused by fluxes are replaced with the phase gain due to multi-loop cyclotron trajectories unavoidably occurring at the fractional filling of 1/p (p is an odd integer). Another approach to composite particles, using so-called vortices, is also discussed from the point of view of the cyclotron braid group description (for both odd and even p integers). PMID:21403293
Self-accelerating Dirac particles and prolonging the lifetime of relativistic fermions
NASA Astrophysics Data System (ADS)
Kaminer, Ido; Nemirovsky, Jonathan; Rechtsman, Mikael; Bekenstein, Rivka; Segev, Mordechai
2015-03-01
The Aharonov-Bohm effect predicts that two parts of the electron wavefunction can accumulate a phase difference even when they are confined to a region in space with zero electromagnetic field. Here we show that engineering the wavefunction of electrons, as accelerating shape-invariant solutions of the potential-free Dirac equation, fundamentally acts as a force and the electrons accumulate an Aharonov-Bohm-type phase--which is equivalent to a change in the proper time and is related to the twin-paradox gedanken experiment. This implies that fundamental relativistic effects such as length contraction and time dilation can be engineered by properly tailoring the initial conditions. As an example, we suggest the possibility of extending the lifetime of decaying particles, such as an unstable hydrogen isotope, or altering other decay processes. We find these shape-preserving Dirac wavefunctions to be part of a family of accelerating quantum particles, which includes massive/massless fermions/bosons of any spin.
Surface-sensitive two-dimensional magneto-fingerprint in mesoscopic Bi2Se3 channels.
Kandala, Abhinav; Richardella, Anthony; Zhang, Duming; Flanagan, Thomas C; Samarth, Nitin
2013-06-12
Periodic Aharonov–Bohm and Altshuler–Aronov–Spivak oscillations have traditionally been observed in lateral transport through patterned mesoscopic loops of diffusive conductors. However, our studies of perpendicular-to-plane magnetotransport in straight-channel, diffusive devices of epitaxial Bi2Se3 surprisingly reveal signatures of Aharonov–Bohm orbits, periodic conductance fluctuation magneto-fingerprints, even though the devices are not explicitly patterned into loops. We show that the length scale of these orbits corresponds to the typical perimeter of triangular terraces found on the surface of these thin film devices, strongly suggesting that the periodic magneto-fingerprint arises from coherent scattering of electron waves from the step-edges. Our interpretation is bolstered by control measurements in devices without such surface morphology that only show a conventional, aperiodic magneto-fingerprint. These results show that lithographically patterned Bi2Se3 devices provide a novel class of mesoscopic physical systems for systematic studies of coherent surface sensitive transport. PMID:23642037
TESE DE DOUTORADO EM ENGENHARIA DE SISTEMAS ELETRNICOS E DE AUTOMAO
de Queiroz, Ricardo L.
TESE DE DOUTORADO EM ENGENHARIA DE SISTEMAS ELETRÔNICOS E DE AUTOMAÇÃO CODIFICAÇÃO DE VÍDEO ESCALONÁVEL EM COMPLEXIDADE E EM ENERGIA Tiago Alves da Fonseca Brasília, agosto de 2012 UNIVERSIDADE DE ENGENHARIA ELÉTRICA CODIFICAÇÃO DE VÍDEO ESCALONÁVEL EM COMPLEXIDADE E EM ENERGIA Tiago Alves da Fonseca
PROGRAMA DE PS-GRADUAO EM MICROELETRNICA UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL
dos Santos, C.A.
PROGRAMA DE PÓS-GRADUAÇÃO EM MICROELETRÔNICA PGMICRO UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL/2004 A Comissão de Pós-Graduação em Microeletrônica em reunião de 19 de março de 2004 e em Reunião do Conselho de (dez) horas de aulas ministradas ao longo do semestre, em disciplinas de graduação de 60 (sessenta
PROGRAMA DE PS-GRADUAO EM MICROELETRNICA UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL
dos Santos, C.A.
PROGRAMA DE PÓS-GRADUAÇÃO EM MICROELETRÔNICA PGMICRO UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL.inf.ufrgs.br/pgmicro Lista, em ordem alfabética, dos selecionados ao curso de Mestrado com ingresso em 2012/01 André Luiz de PósGraduação em Microeletrônica #12;PROGRAMA DE PÓS-GRADUAÇÃO EM MICROELETRÔNICA PGMICRO
MICORRIZA ARBUSCULAR EM ESPÉCIES ARBÓREAS NATIVAS DA BACIA DO RIO TIBAGI, PARANÁ
Waldemar Zangaro; Silvio M. A. Nisizaki; Juliana C. B. Domingos; Emilia M. Nakano
RESUMO: Relata-se a incidência da colonização de micorriza arbuscular (MA) e a resposta à inocu- lação em 81 espécies arbóreas nativas da bacia do rio Tibagi (PR), em condições de casa de vegetação. Também é relatada a incidência da colonização de MA em 51 espécies arbóreas nativas coletadas em áreas em início de sucessão arbórea e no interior da floresta
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ECONOMIA
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÃLIA PROGRAMA DE PÃ?S-GRADUAÃ?Ã?O EM ECONOMIA EDITAL No. 03/2013 SELEÃ?Ã?O DE CANDIDATOS Ã?S VAGAS DO PROGRAMA DE PÃ?S- GRADUAÃ?Ã?O EM ECONOMIA PARA O CURSO DE DOUTORADO ACADÃ?MICO PARA O PRIMEIRO SEMESTRE LETIVO DE 2014 PREÃ?MBULO O Coordenador do Programa de PÃ³s-GraduaÃ§Ã£o em Economia da
Online EM for Unsupervised Models NAACL June 3, 2009
Pratt, Vaughan
Online EM for Unsupervised Models NAACL Â June 3, 2009 Percy Liang Dan Klein #12;Based on a true.2 0.4 0.6 0.8 1.0 accuracy Batch EM 2 #12;Based on a true story Part-of-speech induction: DT NNP NNP VBD The European Commission agreed 20 40 60 80 iterations 0.2 0.4 0.6 0.8 1.0 accuracy Batch EM Online
CARACTERIZAÇÃO DO PERFIL DA APICULTURA EM CAPÃO BONITO E ADJACÊNCIAS
Cristina Fachini; Ricardo Firetti; Eduardo Cardoso De Oliveira; Antonio Assiz De Carvalho Filho
2008-01-01
O Sudoeste Paulista é a segunda maior região do Estado em importância para a apicultura tendo totalizado em 2006 o valor de produção de R$ 3.052.402 com 17.135 colméias. Em 2006 os “produtores de mel” de Capão Bonito existiam “produtores de mel” que tinham a apicultura como principal fonte de renda até agricultores familiares que tinham a produção de mel
CURSO DE PS-GRADUAO EM SENSORIAMENTO REMOTO Coordenador Acadmico
CURSO DE PÓS-GRADUAÇÃO EM SENSORIAMENTO REMOTO (PGSER) Coordenador Acadêmico Elisabete Caria Moraes, Doutora, INPE, 2002 Conselho do Curso Elisabete Caria Moraes - Presidente Flávio Jorge Ponzoni - Membro
CURSO DE PS-GRADUAO EM SENSORIAMENTO REMOTO Coordenador Acadmico
CURSO DE PÓS-GRADUAÇÃO EM SENSORIAMENTO REMOTO (PGSER) Coordenador Acadêmico Flávio Jorge Ponzoni, Doutor, UFPR, 1993 Conselho do Curso Flávio Jorge Ponzoni - Presidente Mauricio Alves Moreira - Membro
Analysis and applicability of the Dutch EMS system into countries developing EMS systems.
Dib, Joe E; Naderi, Sassan; Sheridan, Indrani A; Alagappan, Kumar
2006-01-01
Development of an Emergency Medical Services (EMS) system is a challenging task for administrators, government agencies, and politicians. Factors such as the political climate, governmental support, and monetary resources heavily influence and shape the development of an EMS system. There are various systems in place to meet the functional needs and abilities of different regions while maintaining the basic principle of providing fast attention to those in need, and transportation to a definitive care facility. In this report, we describe the current Dutch EMS system in Amsterdam and the methods of daily pre-hospital health care delivery used, while exploring its potential applicability in developing nations. The Dutch EMS system is a nurse-driven triage system, both at the dispatch level and at the treatment level. Of the approximate yearly 165,000 calls received at the dispatch center, 40% of the requests were triaged based on national protocols such that no emergency ambulance dispatching was necessary. Furthermore, 30% of patients were treated at the scene, and did not subsequently require emergency transport to a definitive care facility. PMID:16434351
REGIMENTO DO CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS, REA DE CONCENTRAO EM
direito a voto; que deverá ser o representante e Coordenador Acadêmico da Área de Concentração e membro do presidente em seus impedimentos temporários) com direito a voto. O coordenador do Conselho de Área de;2 III um representante do Corpo Discente, com direito a voto; Art. 5o Os integrantes do Conselho de
O perfil do médico em formação em radiologia e diagnóstico por imagem
Glauce Cerqueira Corrêa da Silva; Hilton Augusto Koch; Evandro Guimarães de Sousa
2007-01-01
OBJETIVO: Identificar diferenças no perfil psicossocial do especializando e médico residente em radiologia e diagnóstico por imagem, avaliar a aspiração profissional e as motivações internas que os influenciaram a escolher a especialidade radiologia e diagnóstico por imagem e se o nível de satisfação profissional melhora a relação médico-paciente. MATERIAIS E MÉTODOS: Foi aplicado um questionário com 26 perguntas que constava
HISTÓRIA, LITERATURA E DITADURA: O CASO JOÃO PAZ EM INCIDENTE EM ANTARES
Daniela Freitas Torres; Elaine dos Santos
This article refers to a possible critic of the Brazilian military and dictatorial regime in the 1960´s and 1970s, trough the eyes of João Paz, a character in the novel of Erico Veríssimo, Incidente em Antares . The research, from a bibliographic point of view, has been based on recent theories that relate to facts in the History and Literature
EM threat analysis for wireless systems.
Burkholder, R. J. (Ohio State University Electroscience Laboratory); Mariano, Robert J.; Schniter, P. (Ohio State University Electroscience Laboratory); Gupta, I. J. (Ohio State University Electroscience Laboratory)
2006-06-01
Modern digital radio systems are complex and must be carefully designed, especially when expected to operate in harsh propagation environments. The ability to accurately predict the effects of propagation on wireless radio performance could lead to more efficient radio designs as well as the ability to perform vulnerability analyses before and after system deployment. In this report, the authors--experts in electromagnetic (EM) modeling and wireless communication theory--describe the construction of a simulation environment that is capable of quantifying the effects of wireless propagation on the performance of digital communication.
Communication - An Effective Tool for Implementing ISO 14001/EMS
Rachel Damewood; Bowen Huntsman
2004-04-01
The Idaho National Engineering and Environmental Laboratory (INEEL) received ISO 14001/EMS certification in June 2002. Communication played an effective role in implementing ISO 14001/EMS at the INEEL. This paper describes communication strategies used during the implementation and certification processes. The INEEL achieved Integrated Safety Management System (ISMS) and Voluntary Protection Program (VPP) Star status in 2001. ISMS implemented a formal process to plan and execute work. VPP facilitated worker involvement by establishing geographic units at various facilities with employee points of contact and management champions. The INEEL Environmental Management System (EMS) was developed to integrate the environmental functional area into its ISMS and VPP. Since the core functions of ISMS, VPP, and EMS are interchangeable, they were easy to integrate. Communication is essential to successfully implement an EMS. (According to ISO 14001 requirements, communication interacts with 12 other elements of the requirements.) We developed communication strategies that integrated ISMS, VPP, and EMS. For example, the ISMS, VPP, and EMS Web sites communicated messages to the work force, such as “VPP emphasizes the people side of doing business, ISMS emphasizes the system side of doing business, and EMS emphasizes the systems to protect the environment; but they all define work, identify and analyze hazards, and mitigate the hazards.” As a result of this integration, the work force supported and implemented the EMS. In addition, the INEEL established a cross-functional communication team to assist with implementing the EMS. The team included members from the Training and Communication organizations, VPP office, Pollution Prevention, Employee and Media Relations, a union representative, facility environmental support, and EMS staff. This crossfunctional team used various communication strategies to promote our EMS to all organization levels and successfully implemented EMS activities through VPP geographic units. In summary, the ISMS and VPP process at the INEEL provided the basic framework of management support and worker involvement to implement our EMS. A cross-functional communication team was established to facilitate the implementation with great success. Communication has been an effective tool for implementing an ISO 14001/EMS at the INEEL.
AVALIAÇÃO DA PRESENÇA DE ENDOSSIMBIONTES Cardinium em DIFERENTES ESPÉCIES DE ARTRÓPODES.
Technology Transfer Automated Retrieval System (TEKTRAN)
A presença de endossimbiontes do gênero Cardinium em alguns grupos de artrópodes foi recentemente relatada e relacionada com diversas alterações reprodutivas em seus hospedeiros, tais como feminilização de ácaros, partenogênese em parasitóides, incompatibilidade citoplasmática e aumento da fecundida...
Ideas for On-Chip Measurement of EM Interference
Anlage, Steven
Ideas for On-Chip Measurement of EM Interference by R. Jacob Baker Boise State University #12;Noninvasive Ckts Must not interfere with circuit operation Connect to on-chip circuitry Robust operation (tolerant to EM interference) Example: Connect measuring circuit to clock distribution tree. What happens
10 CFR Appendixes E-M to Part 52 - [Reserved
Code of Federal Regulations, 2011 CFR
2011-01-01
10 Energy 2 2011-01-01 2011-01-01 false [Reserved] E Appendixes E-M to Part 52 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS Appendixes E-M to Part 52...
10 CFR Appendixes E-M to Part 52 - [Reserved
Code of Federal Regulations, 2010 CFR
2010-01-01
10 Energy 2 2010-01-01 2010-01-01 false [Reserved] E Appendixes E-M to Part 52 Energy NUCLEAR REGULATORY COMMISSION (CONTINUED) LICENSES, CERTIFICATIONS, AND APPROVALS FOR NUCLEAR POWER PLANTS Appendixes E-M to Part 52...
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ECOLOGIA
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA EDITAL No. 2/2012 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA PARA OS CURSOS DE MESTRADO ACADÊMICO E DOUTORADO ECOLOGIA, no uso de suas atribuições legais, estabelece e torrna público as normas do processo seletivo
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ECOLOGIA
Maier, Rudolf Richard
UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA EDITAL No. 3/2012 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA PARA OS CURSOS DE MESTRADO ACADÊMICO E DOUTORADO Ecologia, no uso de suas atribuições legais, torna público e estabelece a retificação do Edital nº 02
UNIVERSIDADE DE BRASLIA PROGRAMA DE PS-GRADUAO EM ECOLOGIA
Maier, Rudolf Richard
1 UNIVERSIDADE DE BRASÍLIA PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA EDITAL No. 03/2010 SELEÇÃO DE CANDIDATOS ÀS VAGAS DO PROGRAMA DE PÓS-GRADUAÇÃO EM ECOLOGIA PARA OS CURSOS DE MESTRADO ACADÊMICO E DOUTORADO ECOLOGIA no uso de suas atribuições legais, estabelece e torna públicas as normas do processo seletivo para
Asymptotic Distribution of the EMS Option Price Estimator
Jin-Chuan Duan; Geneviève Gauthier; Jean-Guy Simonato
2001-01-01
Monte Carlo simulation is commonly used for computing prices of derivative securities when an analytical solution does not exist. Recently, a new simulation technique known as empirical martingale simulation (EMS) has been proposed by Duan and Simonato (1998) as a way of improving simulation accuracy. EMS has one drawback however. Because of the dependency among sample paths created by the
AVALIAÇÃO BIOMECÂNICA DOS TRABALHADORES EM MARCENARIAS NO DISTRITO
Nilton Cesar Fiedler; Natália S. Menezes; Nuno C. Azevedo; José Reinaldo Moreira da Silva
2003-01-01
A pesquisa foi desenvolvida com base em dados coletados com funcionários de marcenarias no Distrito Federal com o objetivo de fazer uma avaliação biomecânica do trabalhador nas mais diversas máquinas. A avaliação foi feita com a filmagem dos trabalhadores em perfil, avaliação das forças envolvidas e posterior congelamento das imagens e medição dos ângulos das articulações para análise no software
Mecnica Eststica Introduo e Sistemas clssicos em equilbrio, ensembles: microcannico,
Stariolo, Daniel Adrián
Mecânica Estística 2012 Súmula · Introdução e Sistemas clássicos em equilíbrio, ensembles na física e em outras ciências. · Estatísticas quânticas, sistemas de bósons: estatística de Bose-Einstein, sis- temas de férmions: estatística de Fermi-Dirac, exemplos. · Transições de fase: modelos de
Motivac~ao Consist^encia: modelos baseados em dados
Rodriguez, Noemi
Motiva¸c~ao Consist^encia: modelos baseados em dados Consist^encia: modelos baseados do cliente Implementa¸c~ao Localiza¸c~ao de r´eplicas Replica¸c~ao Sistemas Distribu´idos junho de 2013 Replica¸c~ao #12;Motiva¸c~ao Consist^encia: modelos baseados em dados Consist^encia: modelos baseados do cliente
EM algorithm for sparse representation-based image inpainting
Mohamed-jalal Fadili; Jean-luc Starck
2005-01-01
We introduce an expectation-maximization (EM) algorithm for image inpainting based on a penalized likelihood formulated using linear sparse representations. Taking advantage of the sparsity of representations, a regularization through a prior penalty is imposed on the reconstructed coefficients. From a statistical point of view, the inpainting can be viewed as an estimation problem with missing data. The EM framework is
Psiquiatria baseada em evidências Evidence-based psychiatry
Maurício S de Lima; Bernardo GO Soaresb e; Josué Bacaltchuk
Em psiquiatria, observa-se grande variabilidade de práticas clínicas, muitas vezes desnecessária. Essas varia- ções podem estar relacionadas à ausência de evidência científica confiável ou ao desconhecimento das evidên- cias de boa qualidade disponíveis. A medicina baseada em evidências (MBE) é uma combinação de estratégias que busca assegurar que o cuidado individual do paciente seja baseado na melhor informação disponível, a
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM COMBUSTÃO E PROPULSÃO Coordenador Acadêmico do Curso Evandro Marconi Rocco Coordenador da Área de Concentração David dos, USA, 1997 Antonio Osny de Toledo do CTA/IEAV, Doutor, ITA, Brasil, 1996 #12;CURSO DE ENGENHARIA E
CURSO DE PS-GRADUAO EM ENGENHARIA E TECNOLOGIA ESPACIAIS
CURSO DE PÓS-GRADUAÇÃO EM ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE CONCENTRAÇÃO EM COMBUSTÃO E PROPULSÃO Coordenador Acadêmico do Curso Evandro Marconi Rocco Coordenador da Área de Concentração David dos Mendonça do IAE/CTA, Univ. Pennsylvania, USA, 1997 #12;CURSO DE ENGENHARIA E TECNOLOGIA ESPACIAIS ÁREA DE
EM 385-1-1, 2008 Major Changes and Rationale
US Army Corps of Engineers
EM 385-1-1, 2008 Change #6 Major Changes and Rationale Sections 11, 18 and 16 (Cranes and Hoisting, change wording to Powered Industrial Trucks (PITs)/Forklifts and Telehandlers. All PITs and telehandlers (EM 385-1-1, Appendices I, Q and S) · Appendix I, DELETE Rationale: Crane Testing Requirements
ELEKTRA: Um Chatterbot para Uso em Ambiente Educacional
Michelle Denise Leonhardt; Daiane Dorneles de Castro; Liane Margarida; Rockenbach Tarouco
2003-01-01
**** Resumo. A E ducação à Distância vem despertando muito interesse de pesquisadores de diversas áreas. Por isso, também vem sendo muito a bordada em congressos, workshops e seminários. Muito se discute sobre a união entre tecnologia e educação visando complementar a formação de estudantes. Com a pesquisa em Inteligência Artificial, surgiram os chatterbots. Chatterbots são programas destinados a demonstrar
Institutional Design for EMS-Based Government Procurement Policies
Matthew Potoski; Aseem Prakash
2006-01-01
In recent years scholars have highlighted the public policy potential of using voluntary programs based on environmental management systems (EMS) to improve firms' environmental and regulatory performance. While firms receive some benefits for joining EMS-based voluntary programs, these incentives could be strengthened if governments mandated joining such programs as a precondition for participating in government procurement. While we support Arnold
accredited clinical research, EMS and non-operative
Cinabro, David
accredited clinical research, EMS and non-operative sports fellowships to supplement our are magnified by their young wide eyes. I have had many come back to me later--most of whom I do not recall and nationally. In my short time in the SIC world, I have had the opportunity to view the other EM departments
An approximate EM Homographical Iterative Closest Point algorithm
Markus Louw; Fred Nicolls
This paper describes an approximately expectation- maximization (EM) formulation of a homographical iterative closest point registration approach (henceforth HICP). We show that such an EM approach allows the algorithm to converge faster, and more robustly in the presence of noise. Although this algorithm can register points transformed by a more general set of linear transformations than the original Iterative Closest
Cytogenetic characterization of the CHO mutant EM9
Dillehay, L.E.; Thompson, L.H.; Carrano, A.V.
1983-12-12
A remarkable property of the Chinese hamster ovary mutant EM9 is its very high baseline frequency of sister-chromatid exchange (SCE), about 110 per cell. EM9 is also hypersensitive (7-fold) to the induction of SCE by EMS. The high baseline SCE frequency in EM9 appears to be the result of a single mutational event. DNA replication in EM9 and AA8 was studied using pulse labeling and alkaline elution. After a 1 hour labeling period, the majority of the labeled DNA elutes rapidly indicating the small size of the nascent single-stranded molecules. In the absence of BradUrd substitution more than 50% of the labeled DNA is retained on the filter after a 1 hour chase.
Contour extracting with combination particle filtering and EM algorithm
NASA Astrophysics Data System (ADS)
Meng, Bo; Zhu, Ming
2008-03-01
The problem of extracting continuous structures from images is a difficult issue in early pattern recognition and image processing. Tracking with contours in a filtering framework requires a dynamical model for prediction. Recently, Particle filter, is widely used because its multiple hypotheses and versatility within framework. However, the good choice of the propagation function is still its main problem. In this paper, an improved particle filter, EM-PF algorithm is proposed which using the EM (Expectation-Maximization) algorithm to learn the dynamical models. The EM algorithm can explicitly learn the parameters of the dynamical models from training sequences. The advantage of using the EM algorithm in particle filter is that it is capable of improve tracking contour by having accurate model parameters. Though the experiment results, we show how our EM-PF can be applied to produces more robust and accurate extracting.
Eloi Junior Damke; Queila Regina Souza
Resumo: A questão da Responsabilidade Social corporativa tem sido considerada, entre muitos autores da área da administração , como um tema de relevância crescente na formulação de estratégias empresariais. Considerando o contexto atual em que se fundamentam estas proposições, este trabalho procura relacionar alguns dos principais argumentos favoráveis e desfavoráveis à responsabilida de social das empresas privadas, em especial aquelas
Hanford Site performance summary: EM funded programs
Edwards, C.
1995-09-01
Hanford performance at fiscal year end reflects a three percent unfavorable schedule variance ($46.3 million*) which was an improvement over August 1995 ($46.3 million for September versus $65.9 million for August) and is below established reporting thresholds (greater than 3 percent). The majority of the behind schedule condition (53 percent) is attributed to EM-40 (Office of Environmental Restoration [ER]) and is a result of late receipt of funds, procurement delays, and US Army Corps of Engineers (USACE) work planned but not accomplished. Other primary contributors to the behind schedule condition are associated with tank farm upgrades, high-level waste disposal and work for others (support to the US Department of Energy-Headquarters [DOE-HQ]). The remaining behind schedule condition is distributed throughout the remaining Hanford programs and do not share common causes. A breakdown of individuals listed on page 8.
Occupational infectious disease exposures in EMS personnel.
Reed, E; Daya, M R; Jui, J; Grellman, K; Gerber, L; Loveless, M O
1993-01-01
Reports of occupationally transmitted hepatitis B virus (HBV) and human immunodeficiency virus (HIV) prompted the Portland Bureau of Fire Rescue and Emergency Services (PFB) to institute a comprehensive program for handling and tracking on-the-job infectious disease exposures. Data were collected for a 2-year period beginning January 1, 1988, and ending December 31, 1989, utilizing verbal and written exposure reports, prehospital care reports, and PFB statistical information. Two hundred and fifty-six (256) exposures were categorized. The overall incidence of reported exposure was 4.4/1,000 emergency medical service (EMS) calls. Of these exposures, 14 (5.5%) were needle sticks, 15 (5.9%) were eye splashes, 8 (3.1%) were mucous membrane exposures, 38 (14.8%) were exposure to nonintact skin, 120 (46.9%) were exposures to intact skin, and 61 (23.8%) involved respiratory exposure only. The incidence of exposure of nonintact skin or mucous membranes to blood or body fluids and needle sticks was 1.3/1,000 EMS calls. Forty-eight individuals (64% of those incurring needle sticks, or exposure of non-intact skin or mucous membranes to blood or body fluids) were treated and followed for signs of infection. Of this group, 11 individuals (26%) previously vaccinated against hepatitis B demonstrated inadequate HBsAb titers at the time of exposure. Requests for HIV and HBV information on source patients were made for needle sticks or exposure of nonintact skin or mucous membranes to blood or high-risk body fluids. Information on the source patient's HIV status was obtained for 57% of these requests.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:8445190
Cristhine L. Chagas; Diego G. Figuerôa; Ênio H. Rios; Gérson Carvalho; Gustavo Mascarenhas; Ives D. Barbosa; João M. Braghiroli; João N. Tupiná; Mariana F. Miranda; Naiara A. Fraga; Luis F. Adan
2007-01-01
A Síndrome Metabólica caracteriza-se pela associação de fatores de risco cardiovascular, como obesidade, resistência à insulina, dislipidemia e hipertensão arterial. Sua prevalência geral em crianças e adolescentes norte-americanos é de 3-4%, mas atinge 28,7% naqueles com Índice de Massa Corpórea (IMC) = percentil 95. Observa-se que os fatores predisponentes à síndrome se manifestam desde a vida intra-uterina. Apesar de bem
PROTOCOLO DE COLETA DE MATERIAL BIOLGICO PARA ESTUDOS DE GENTICA MOLECULAR EM CARNVOROS E OUTROS
Eizirik, Eduardo
PROTOCOLO DE COLETA DE MATERIAL BIOLÓGICO PARA ESTUDOS DE GENÉTICA MOLECULAR EM CARNÍVOROS E OUTROS encontrados mortos (p. ex. em estradas), peles apreendidas e qualquer outro material disponível. Apesar de a ênfase atual de nossas pesquisas em genética ser em carnívoros neotropicais, pesquisas similares com
INVERSION OF EM DATA TO RECOVER 1-D CONDUCTIVITY AND A GEOMETRIC SURVEY PARAMETER
Oldenburg, Douglas W.
INVERSION OF EM DATA TO RECOVER 1-D CONDUCTIVITY AND A GEOMETRIC SURVEY PARAMETER By Sean Eugene electromagnetic (EM) data. There are two types of data which are of particular interest: airborne EM (AEM) and ground based horizontal loop EM (HLEM). When dealing with AEM data there is a potential for errors
PROGRAMA DE PS-GRADUAO EM MICROELETRNICA UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL
dos Santos, C.A.
PROGRAMA DE PÓS-GRADUAÇÃO EM MICROELETRÔNICA PGMICRO UNIVERSIDADE FEDERAL DO RIO GRANDE DO SUL/2007 A Comissão de Pós-Graduação em Microeletrônica, no uso de suas atribuições regimentais, em reunião realizada, para participação de alunos e professores permanentes em congressos nacionais e internacionais, e dá
Polygonal Approximation of Laser Range Data Based on Perceptual Grouping and EM
Latecki, Longin Jan
Polygonal Approximation of Laser Range Data Based on Perceptual Grouping and EM Longin Jan Latecki Maximization (EM) step. By evaluating EM approximation quality we are able to recognize a locally optimal solution, and modify the number of model components and their parameters. Consequently, EM can converge