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Articles 1 - 9 of 9
Full-Text Articles in Atomic, Molecular and Optical Physics
Enhancement Of Electron-Positron Pair Creation Due To Transient Excitation Of Field-Induced Bound States, M Jiang, Q Z. Lv, Z M. Sheng, Rainer Grobe, Qichang Su
Enhancement Of Electron-Positron Pair Creation Due To Transient Excitation Of Field-Induced Bound States, M Jiang, Q Z. Lv, Z M. Sheng, Rainer Grobe, Qichang Su
Faculty publications – Physics
We study the creation of electron-positron pairs induced by two spatially separated electric fields that vary periodically in time. The results are based on large-scale computer simulations of the time-dependent Dirac equation in reduced spatial dimensions. When the separation of the fields is very large, the pair creation is caused by multiphoton transitions and mainly determined by the frequency of the fields. However, for small spatial separations a coherence effect can be observed that can enhance or reduce the particle yield compared to the case of two infinitely separated fields. If the travel time for a created electron or positron …
Pair Creation For Bosons In Electric And Magnetic Fields, Q Z. Lv, A C. Su, M Jiang, Rainer Grobe, Qichang Su
Pair Creation For Bosons In Electric And Magnetic Fields, Q Z. Lv, A C. Su, M Jiang, Rainer Grobe, Qichang Su
Faculty publications – Physics
By solving the quantum field theoretical version of the Klein-Gordon equation numerically, we study the creation process for charged boson-antiboson pairs in static electric and magnetic fields. The fields are perpendicular to each other and spatially localized along the same direction, which permits us to study the crucial impact of the magnetic field's spatial extension on dynamics. If its width is comparable to that of the electric field, we find a magnetically induced Lorentz suppression of the pair-creation process. When the width is increased such that the created bosons can revisit the interaction region, we find a region of exponential …
Suppression Of Pair Creation Due To A Steady Magnetic Field, W Su, M Jiang, Z Q. Lv, Rainer Grobe, Qichang Su
Suppression Of Pair Creation Due To A Steady Magnetic Field, W Su, M Jiang, Z Q. Lv, Rainer Grobe, Qichang Su
Faculty publications – Physics
We investigate the electron-positron pair creation process in a supercritical static electric field in the presence of a static magnetic field that is perpendicular. If both fields vary spatially in one direction the dynamics can be reduced to a set of one-dimensional systems. Using a generalized computational quantum field theoretical procedure, we calculate the time dependence of the spatial density for the created electrons. In the presence of the magnetic field, a significant amount of suppression of pair creation is observed in the simulations and confirmed by an analytical analysis for the limits of short-range fields and long interaction times. …
Pair Creation Enhancement Due To Combined External Fields, M Jiang, W Su, Z Q. Lv, X Lu, Y J. Li, Rainer Grobe, Qichang Su
Pair Creation Enhancement Due To Combined External Fields, M Jiang, W Su, Z Q. Lv, X Lu, Y J. Li, Rainer Grobe, Qichang Su
Faculty publications – Physics
We study the creation of electron-positron pairs from the vacuum induced by a combination of a static electric field and an alternating field. We find that the overall pair production can be increased by two orders of magnitude compared to the yields associated with each field individually. We examine the interesting case where both fields are spatially localized, permitting us to examine the time evolution of the spatial density for the created particle pairs. We find that there are a variety of competing mechanisms that contribute to the total yield.
Electron-Positron Pair Creation Induced By Quantum-Mechanical Tunneling, M Jiang, W Su, X Lu, Z M. Sheng, Y T. Li, J Zhang, Rainer Grobe, Qichang Su
Electron-Positron Pair Creation Induced By Quantum-Mechanical Tunneling, M Jiang, W Su, X Lu, Z M. Sheng, Y T. Li, J Zhang, Rainer Grobe, Qichang Su
Faculty publications – Physics
We study the creation of electron-positron pairs from the vacuum induced by two spatially displaced static electric fields. The strength and spatial width of each localized field is less than required for pair creation. If, however, the separation between the fields is less than the quantum-mechanical tunneling length associated with the corresponding quantum scattering system, the system produces a steady flux of electron-positron pairs. We compute the time dependence of the pair-creation probability by solving the Dirac equation numerically for various external field sequences. For the special case of two very narrow fields we provide an analytical expression for the …
Bosonic Analog Of The Klein Paradox, R E. Wagner, M R. Ware, Q Su, Rainer Grobe
Bosonic Analog Of The Klein Paradox, R E. Wagner, M R. Ware, Q Su, Rainer Grobe
Faculty publications – Physics
The standard Klein paradox describes how an incoming electron scatters off a supercritical electrostatic barrier that is so strong that it can generate electron- positron pairs. This fermionic system has been widely discussed in textbooks to illustrate some of the discrepancies between quantum mechanical and quantum field theoretical descriptions for the pair creation process. We compare the fermionic dynamics with that of the corresponding bosonic system. We point out that the direct counterpart of the Pauli exclusion principle (the central mechanism to resolve the fermionic Klein paradox) is stimulated emission, which leads to the resolution of the analogous bosonic paradox.
Pair Creation Rates For One-Dimensional Fermionic And Bosonic Vacua, T Cheng, M R. Ware, Q Su, Rainer Grobe
Pair Creation Rates For One-Dimensional Fermionic And Bosonic Vacua, T Cheng, M R. Ware, Q Su, Rainer Grobe
Faculty publications – Physics
We compare the creation rates for particle-antiparticle pairs produced by a supercritical force field for fermionic and bosonic model systems. The rates obtained from the Dirac and Klein-Gordon equations can be computed directly from the quantum-mechanical transmission coefficients describing the scattering of an incoming particle with the supercritical potential barrier. We provide a unified framework that shows that the bosonic rates can exceed the fermionic ones, as one could expect from the Pauli-exclusion principle for the fermion system. This imbalance for small but supercritical forces is associated with the occurrence of negative bosonic transmission coefficients of arbitrary size for the …
Interpretational Difficulties In Quantum Field Theory, P Krekora, Q Su, Rainer Grobe
Interpretational Difficulties In Quantum Field Theory, P Krekora, Q Su, Rainer Grobe
Faculty publications – Physics
Based on space-time-resolved solutions to relativistic quantum field theory we illustrate interpretational difficulties in associating field-theoretical quantities with properties of particles. These difficulties are related to the fact that the definition of the spatial probability density of particles depends on the choice of the Hilbert subspace on which the field operator is projected. We illustrate these problems by analyzing pair-production probabilities and spatial densities for the electron-positron dynamics associated with a spatially localized subcritical potential that is turned on and off in time.
Classical Versus Quantum Dynamics For A Driven Relativistic Oscillator, Rainer Grobe, Qichang Su, P J. Peverly, R E. Wagner
Classical Versus Quantum Dynamics For A Driven Relativistic Oscillator, Rainer Grobe, Qichang Su, P J. Peverly, R E. Wagner
Faculty publications – Physics
We compare the time evolution of the quantum-mechanical spatial probability density obtained by solving the time-dependent Dirac equation with its classical counterpart obtained from the relativistic Liouville equation for the phase-space density in a regime in which the dynamics is essentially relativistic. For a resonantly driven one-dimensional harmonic oscillator, the simplest nontrivial model system to perform this comparison, we find that, despite the nonlinearity induced by relativity, the classical ensemble description matches the quantum evolution remarkably well.