Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 35 for “"Wave packets"”.
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Nondispersive wave packets
In this work, nondispersive wave packet solutions to linear partial differential equations are investigated. These solutions are characterized by infinite energy content; otherwise, they are continuous, nonsingular and propagate in free space without spreading out. Examples of such solutions are …
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High Angular Momentum Rydberg Wave Packets
High angular momentum Rydberg wave packets are studied. Application of carefully tailored electric fields to low angular momentum, high- n ( n ∼ 300) Rydberg atoms creates coherent superpositions of Stark states with near extreme values of angular momentum, [cursive l]. Wave packet components orbit …
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Energy and information transfer via coherent exciton wave packets
… it may be possible to construct excitonic wave packets that offer a means of efficiently transmitting information and energy. This thesis is a combined theory/computation investigation to design condensed matter systems which support the requisite coherent transport. Under the idealizing …
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Approximation of wave packets on the whole real line
… well does the chosen basis function approximate wave packets? Chapter 1 provides the necessary background to understand the motivation and results presented in the subsequent chapters. In Chapters 2, 3 and 4 we derive asymptotic estimates of the expansion coefficients for a wave packet in …
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Excitation of wave packets and random disturbances in a boundary layer
A study on the behaviour of wave-packets and random disturbances, introduced by the vibrating-ribbon technique in a Blasius boundary layer, is presented. The experiments were conducted in the VPI & SU low turbulence wind tunnel. The flat plate model was constructed from an aluminum-paper honeycomb …
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Dynamics of interfering wave packets in rubidium by high resolution quantum beat spectroscopy
… spectroscopy has been realized to study atomic wave packet dynamics. Wave packets comprising pairs of low quantum number (n = 5 - 8) electronic states were formed in Rb vapor with ultrafast laser pulses, and their dynamics was observed by an all-optical technique of parametric four wave mixing …
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Hypersound interaction studied by time-resolved inelastic light and x-ray scattering
… acoustic phonons, also called hypersonic waves. To generate such high frequency phonons, femtosecond near infrared laser pulses were used to heat nanostructures composed of perovskite oxides on an ultrashort timescale. As a consequence the heated regions of such a nanostructure expand and …
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Chaotic behavior and energy polarisation in flatband lattice models
… symmetries, resulting in compactly localised wave functions to just a few lattice sites. The existence of FBs in materials entails high sensitivity to the initial conditions of the system, especially with regard to disorder and nonlinear- ity. In this study, we numerically investigate the wave …
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Helical waves in Earth's outer core
… addresses the generation and dispersion of wave packets in Earth's outer core. The waves of interest feed off the buoyancy field, and are supported by strong rotation and/or a large-scale magnetic field, two key features of the dynamics in Earth's core. We aim to better understand the role …
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Attosecond Wave Packet Metrology
… and molecules for the creation of ultrashort wave packets. Free electron wave packets can be controlled by an external laser field and driven to scatter off their parent ions. They also carry information on the atomic structure, which enables the phase-resolved characterization of unknown …
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High-Resolution Seismic Characterization of Shallow Sedimentary Structure for Freshwater Resources and Karstic Voids
… configurations. The study reveals distinct P-wave dominant frequencies for each source and geometry, along with direct S-wave arrivals for the Ballard source. Signal-to-noise ratios (SNR) are determined, and source radiation patterns and signature wavelets are analyzed, providing valuable …
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Long-range Propagation, Interaction, and Dissipation of Small-Scale Gravity Waves in the Mesosphere and Lower Thermosphere
… and interaction of small-scale gravity waves in the Mesosphere and Lower Thermosphere (MLT) region. The research in this thesis is made up of three distinct studies which build upon each other. The first investigates the thermospheric dissipation of three gravity wave packets …
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Rotating Nonlinear States in Gross-Pitaevskii Equations
… (1) Approximate solutions known as semiclassical wave packets to weakly nonlinear Schr\"odinger equations with rotation. (2) Existence and dynamical properties of rotating bound state solutions in both mass-subcritical and mass-supercritical regimes. The organization of the thesis is as follows: …
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Chaotic behaviour of disordered nonlinear lattices
… by performing extensive numerical simulations of wave packet evolutions in the various dynamical regimes exhibited by these models. In particular, we compare the computational efficiency of the integrators considered by checking their ability to correctly reproduce the time evolution of the …
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Nonlinear dynamics and chaos in multidimensional disordered Hamiltonian systems
… diffusive spreading of initially localized wave packets whose extent (measured for instance through the wave packet's second moment m2) grows in time t as t αm with 0 < αm < 1. However, the characteristics and the asymptotic fate of such evolutions still remain an issue of intense debate due …
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Spectral properties of planar helium under periodic driving
… for the existence of nondispersive two-electron wave packets which propagate along the associated periodic orbit. This represents a highly nontrivial qualitative confirmation of earlier calculations on a 1D model atom, though with important enhancements of the decay rate of these atomic …
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Bose-Einstein Condensates in a Single Double Well Potential
… split in a double well potential into two matter wave packets, which are coupled coherently to each other via quantum mechanical tunneling of atoms through the barrier. The state of the system can be described by two dynamical variables, the population imbalance of the two wells and their phase …
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The scattering and shrinking of a Gaussian wave packet by delta function potentials
… by a random potential causes localization of wave functions, and that this localization is governed by the Born postulate of quantum mechanics. We begin with a simple model system: a one-dimensional Gaussian wave packet incident from the left onto a delta function potential with a single …
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Ultrafast Dynamics and Nonlinear Interactions in Alkali Atoms and Diatomics
… D states of the Cesium dimer and to study atomic wavepackets and nonlinear effects in Rubidium and Potassium. Two color, pump-probe techniques have been used to probe the time evolution of wavepackets in the B, C, and D rovibrational levels of Cs$\sb2$. The temporal history of the wavepacket is …
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Quantum evolution: The case of weak localization for a 3D alloy-type Anderson model and application to Hamiltonian based quantum computation
… disorder in a crystal can cause non-spreading of wave packets, which is one possible mechanism (at single electron level) to explain metalinsulator transitions. The theory of quantum computation promises to bring greater computational power over classical computers by making use of some special …
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