Дисертації з теми "Reconnection of quantum vortices"
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Rorai, Cecilia. "Vortex reconnection in superfluid helium." Doctoral thesis, Università degli studi di Trieste, 2012. http://hdl.handle.net/10077/7868.
Повний текст джерелаLa presente tesi concerne la modellizzazione e simulazione numerica, attraverso l'equazione di Gross-Pitaevskii (chiamata anche equazione di Schroedinger non lineare), della dinamica dei vortici quantistici nell'elio superfluido e in particolare del fenomeno della riconnessione. La riconnessione si verifica qualora due vortici approssimativamente antiparalleli, si intersecano e si scambiano le estremità. Questo fenomeno è stato osservato sperimentalmente e risulta essere una caratteristica essenziale della turbolenza quantistica.
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Beardsell, Guillaume. "Spectral simulations of the reconnection process of two vortices." Master's thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/26651.
Повний текст джерелаCe mémoire investigue le phénomène de reconnexion visqueuse de deux tourbillons initialement placés de façon orthogonale ou antiparallèle. Les équations de Navier-Stokes pour un fluide incompressible sont résolues directement (DNS) à l’aide d’un algorithme pseudospectral utilisant des expansions périodiques dans les trois directions cartésiennes. La condition de circulation nulle inhérente à cette méthode numérique est contournée en résolvant les équations dans un repère tournant approprié. Une méthode simple utilisant des lignes de vorticité est proposée afin de calculer le pourcentage de reconnexion instantané η de deux tourbillons. Cette méthode est également employée pour séparer le champ de vorticité en ses composantes reconnectées et non-reconnectées, ce qui facilite l’identification visuelle des différentes étapes du processus de reconnexion. Finalement, l’échelle de temps de la reconnexion tourbillonnaire Trec est calculée pour différents nombres de Reynolds (500 ≤ Re ≤ 10000). Il est trouvé que l’ordre de grandeur de Trec varie de façon continue de [symbol] à mesure que Re augmente.
This work focuses on the viscous reconnection phenomenon of two vortex tubes that are initially antiparallel or orthogonal to each other. The incompressible Navier-stokes equations are solved directly (DNS) using a Fourier pseudospectral algorithm with triply periodic boundary conditions. The associated zero-circulation constraint is circumvented by solving the governing equations in a proper rotating frame of reference. A simple method using vortex lines is proposed to compute the instantaneous reconnection level η of two vortices. The proposed method is also used to split the vorticity field into its reconnected and non-reconnected parts, which allows for a clear and intuitive visual identification of the different reconnection phases. Finally, the Reynolds number dependence of the reconnection timescale Trec is investigated for 500 ≤ Re ≤ 10000. The scaling is found to vary continuously as Re is increased from [symbol].
Santos, André Cidrim. "Quantum turbulence and multicharged vortices in trapped atomic superfluids." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-31012018-154136/.
Повний текст джерелаNesta tese, investigamos numericamente a turbulência quântica em condensados de Bose- Einstein (BECs) aprisionados. Discutimos, inicialmente, a caracterização qualitativa apropriada para estes sistemas, mostrando a limitação de analogias tipicamente feitas com hidrodinâmica clássica e turbulência em grandes sistemas com Hélio superfluido. Devido às suas limitadas escalas espaciais, os sistemas investigados somente podem exibir o tipo de turbulência conhecida como ultra-quântica (ou de Vinen). Em seguida, propomos sistemas experimentalmente factíveis que permitem investigações mais controladas da turbulência, fazendo uso da instabilidade dinâmica de vórtices multi-carregados como ponto de partida para geração de dinâmicas complexas. Em duas dimensões, nossa proposta permite controle sobre a polarização de vórtices em sistemas aprisionados em potencial harmônico. Este arranjo é então utilizado no estudo do decaimento da turbulência nesse contexto, através de um modelo fenomenológico para equação que descreve a taxa de variação do número de vórtices. Como consequência, pudemos verificar que a aniquilação de vórtices dá-se através de um processo que envolve quatro vórtices. Em três dimensões, apresentamos um estudo do decaimento de um vórtice de carga topológica quatro, também em potencial harmônico. Mantendo em mente esse sistema a título de comparação, propomos um cenário turbulento, quase-isotrópico, partindo de um estado inicial formado por dois vórtices duplamente carregados, mas orientados anti-paralelamente. Verificamos que a turbulência decorrente desse arranjo coincide com a regime de Vinen analisando características do seu decaimento, especificamente obtendo o espectro de energia [E(k) ∼ k1] e evolução temporal da densidade de linhas de vórtices [L(t) ∼ t1]. Apesar de que essas características são comumente encontradas no contexto de Hélio superfluido, apresentamos pela primeira vez essa identificação no cenário realístico de BEC aprisionados.
Tang, Jian-Ming. "Quantum mechanics of quantized vortices in dilute Bose gases /." Thesis, Connect to this title online; UW restricted, 2001. http://hdl.handle.net/1773/9682.
Повний текст джерелаStagg, George William. "A numerical study of vortices and turbulence in quantum fluids." Thesis, University of Newcastle upon Tyne, 2016. http://hdl.handle.net/10443/3340.
Повний текст джерелаTejada, J., S. Velez, and R. Zarzuela. "Quantum Nanomagnetism." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35358.
Повний текст джерелаHIENTZSCH, LARS ERIC. "Non linear Schrödinger equations and quantum fluids non vanishing at infinity: incompressible limits and quantum vortices." Doctoral thesis, Gran Sasso Science Institute, 2019. https://hdl.handle.net/20.500.12571/26564.
Повний текст джерелаAnzolin, Gabriele. "Astronomical applications of optical vortices." Doctoral thesis, Università degli studi di Padova, 2009. http://hdl.handle.net/11577/3426036.
Повний текст джерелаI vortici ottici rappresentano una particolare classe di dislocazioni dei fronti d'onda caratterizzate da una carica topologica l. La superficie di fase costante di un'onda elettromagnetica che trasporta un vortice ottico ha una struttura elicoidale. Lungo l'asse di questa elica è presente una singolarità in cui la fase non può essere definita. Di conseguenza, la distribuzione d'intensità di un fascio di luce contenente un vortice ottico presenta una zona centrale dove l'intensità è nulla per effetto dell’interferenza distruttiva. I vortici ottici possono essere prodotti utilizzando particolari elementi ottici detti phase modifying devices che modificano la fase di un'onda incidente. I più efficienti tra questi sono i fork holograms (ologrammi) e le spiral phase plates (maschere di fase). Negli ultimi anni, le proprietà dei vortici ottici hanno trovato interessanti applicazioni nei campi della fisica e dell'ottica. Tra queste, le più promettenti sono quelle in comunicazioni ottiche, nelle nanotecnologie ed in biologia. Recentemente, i vortici ottici stanno suscitando un crescente interesse anche nella comunità astronomica. Infatti, queste particolari proprietà della radiazione elettromagnetica potrebbero permettere di studiare diversi fenomeni astrofisici da un punto di vista completamente nuovo. In questa Tesi vengono presentate alcune possibili applicazioni dei vortici ottici in strumentazione astronomica. In particolare, lo scopo principale di questo lavoro è lo sviluppo di nuove tecniche che permetteranno di migliorare le prestazioni di sistemi ottici. In primo luogo, viene proposto un metodo per aumentare il potere risolutivo di un telescopio limitato dalla diffrazione che prevede l'utilizzo di un fork hologram con una singola dislocazione. I risultati di esperimenti e simulazioni numeriche rivelano che la sovrapposizione dei vortici ottici prodotti da due fasci di luce con una distribuzione d'intensità di Airy mostra già un'evidente asimmetria quando la separazione è di un ordine di grandezza inferiore rispetto al limite posto dal criterio di Rayleigh. Questo risultato è stato ottenuto sia in luce monocromatica, sia in luce bianca. Viene poi presentato il primo esperimento astronomico in cui sono stati prodotti vortici ottici con un fork hologram avente una singola dislocazione posto al piano focale del telescopio Galileo da 122 cm di Asiago. Utilizzando i principi del Lucky Imaging per ridurre gli effetti provocati da condizioni di seeing mediocre, sono state osservate le immagini dei vortici ottici prodotti dalle due componenti principali del sistema multiplo alfa Her, in luce non monocromatica, e dalla stella singola alfa Boo, utilizzando un filtro spaziale a banda stretta. In entrambi i casi, i profili d’intensità dei vortici ottici osservati sono riproducibili con simulazioni numeriche. La sensibilità dell'immagine di un vortice ottico prodotto con un phase modifying device rispetto a spostamenti fuori asse del fascio entrante è confermata da modelli analitici dettagliati e anche da simulazioni numeriche, specialmente nel caso in cui vengano utilizzati elevati valori della cariche topologica l. Questa proprietà potrebbe essere utilizzata per fare misure astrometriche da terra con una precisione che potrebbe competere con quella fornita dalle tecniche standard di astrometria di PSF. La sensibilità rispetto a piccoli spostamenti fuori asse potrebbe anche essere sfruttata per migliorare la correzione dell’aberrazione di tip/tilt del fronte d'onda in un piccolo campo di vista. Viene poi discussa la possibile applicazione di vortici ottici con carica topologica pari nella coronografia ad alto contrasto. In questo caso, l'azione combinata di una spiral phase plate e di un diaframma circolare utilizzato come stop di Lyot permette di annullare totalmente la luce di una stella in asse. Studi teorici indicano che il coronografo a vortici ottici è uno dei pochi che potrebbe realmente permettere l'osservazione diretta di pianeti extrasolari di tipo terrestre. Purtroppo, questa notevole proprietà è fortemente limitata dalle attuali tecniche usate per produrre le spiral phase plate. Nell'ambito di un progetto di costruzione di un coronografo a vortici ottici con l = 2 ottimizzato per lunghezze d'onda visibili, vengono presentati i risultati di simulazioni numeriche ottenuti considerando una spiral phase plate la cui superficie è suddivisa in N livelli discreti. Infine, vengono discusse le procedure sperimentali utilizzate per testare spiral phase plates in PMMA (polimetil-metacrilato).
Samson, Edward Carlo Copon. "Generating and Manipulating Quantized Vortices in Highly Oblate Bose-Einstein Condensates." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/228499.
Повний текст джерелаZarzuela, Fernández Ricardo. "Novel quantum phenomena and excitation modes in type-I superconductors and magnetic vortices." Doctoral thesis, Universitat de Barcelona, 2014. http://hdl.handle.net/10803/285263.
Повний текст джерелаEl objetivo de esta tesis ha sido estudiar fenómenos cuánticos y modos de excitación en superconductores tipo-I y vórtices magnéticos. La irreversibilidad magnética en muestras de plomo con forma de disco en el estado intermedio ha sido explorada mediante medidas de ciclos de histéresis a diferentes temperaturas, medidas de las curvas de magnetización zero-field-cooled y field-cooled a diferentes campos y relajaciones magnéticas a lo largo de la rama descendiente de los ciclos de histéresis. Se han observado relajaciones magnéticas independientes de la temperatura en estas muestras, las cuales se atribuyen al efecto túnel de las interficies normal-superconductor a través de barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde la interfície se trata como una variedad 2D elástica que se ancla a defectos planares. La barrera de anclaje se puede controlar mediante la inyección de supercorriente en el sistema. El núcleo del estado vórtice muestra una naturaleza elástica a lo largo de la dirección axial de los discos magnéticos que lo presentan como estado fundamental. Se ha estudiado bajo qué condiciones el modo girótropo es compatible con una dispersión espacial semejante a las ondas de espín de longitud de onda finita presentes en un ferromagneto. El espectro de excitaciones axiales presenta dos ramas bien definidas, una asociada al modo girótropo y la otra originada por la existencia de una masa efectiva asociada al núcleo. También se ha explorado la irreversibilidad magnética del estado vórtice mediante un protocolo análogo al de los superconductores tipo-I. De nuevo se ha observado un comportamiento no térmico a bajas temperaturas en las relajaciones magnéticas, el cual es atribuido al efecto túnel de un segmento del núcleo vorticial a través de las barreras de anclaje. Un modelo de efecto túnel basado en la teoría de Caldeira-Leggett para sistemas disipativos se ha construido para explicar estas observaciones experimentales, donde el núcleo vorticial se trata como una variedad 1D elástica anclada a un defecto lineal. Por último, se ha estudiado cuál sería el efecto del estado vórtice sobre la supercorriente de una unión Josephson si como capa no superconductora se escogiera un disco magnético con este estado fundamental. Se ha concluido que la variación de la corriente Josephson con desplazamientos pequeños del núcleo vorticial es detectable experimentalmente.
Neely, Tyler William. "Formation, Dynamics, and Decay of Quantized Vortices in Bose-Einstein Condensates: Elements of Quantum Turbulence." Diss., The University of Arizona, 2010. http://hdl.handle.net/10150/194178.
Повний текст джерелаJason, Peter. "Theoretical studies of Bose-Hubbard and discrete nonlinear Schrödinger models : Localization, vortices, and quantum-classical correspondence." Doctoral thesis, Linköpings universitet, Teoretisk Fysik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-129564.
Повний текст джерелаKoller, J. "Potential Vorticity Evolution in the Co-orbital Region of Embedded Protoplanets." Los Alamos, N.M. : Oak Ridge, Tenn. : Los Alamos National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/836124-uO0DBZ/native/.
Повний текст джерелаPublished through the Information Bridge: DOE Scientific and Technical Information. "LA-14149-T" J. Koller. US DOE (US) 09/01/2004. Report is also available in paper and microfiche from NTIS.
Bleu, Olivier. "Physics of quantum fluids in two-dimensional topological systems." Thesis, Université Clermont Auvergne (2017-2020), 2018. http://www.theses.fr/2018CLFAC044/document.
Повний текст джерелаThis thesis is dedicated to the description of both single-particle and bosonic quantum fluid Physics in topological systems. After introductory chapters on these subjects, I first discuss single-particle topological phenomena in honeycomb lattices. This allows to compare two theoretical models leading to quantum anomalous Hall effect for electrons and photons and to discuss the photonic quantum valley Hall effect at the interface between opposite staggered cavity lattices.In a second part, I present some phenomena which emerge due to the interplay of the linear topological effects with the presence of interacting bosonic quantum fluid described by mean-field Gross-Pitaevskii equation. First, I show that the spin-anisotropic interactions lead to density-driven topological transitions for elementary excitations of a condensate loaded in the polariton quantum anomalous Hall model (thermal equilibrium and out-of-equilibrium quasi-resonant excitation configurations). Then, I show that the vortex excitations of a scalar condensate in a quantum valley Hall system, contrary to linear wavepackets, can exhibit a robust chiral propagation along the interface, with direction given by their winding in real space, leading to an analog of quantum spin Hall effect for these non-linear excitations. Finally, coming back to linear geometrical effects, I will focus on the anomalous Hall effect exhibited by an accelerated wavepacket in a two-band system. In this context, I present a non-adiabatic correction to the known semiclassical equations of motion which can be expressed in terms of the quantum geometric tensor elements. We also propose a protocol to directly measure the tensor components in radiative photonic systems
Villerot, Sophie. "Structure microscopique et dynamique des vortex dans un superfluide dense." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00775920.
Повний текст джерелаTeles, Rafael Poliseli. "Comportamento de condensados de Bose-Einstein aprisionados, na presença de vórtices e modos coletivos." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-16062015-142359/.
Повний текст джерелаThe extension of quantum phenomena into macroscopic scales is responsible for a whole class of effects such as superconductivity, superfluidity, and Bose-Einstein condensation, which played central roles in physics throughout the last century. The production of the first Bose-Einstein condensates made possible the realization of experiments involving macroscopic quantum phenomena with an unprecedented level of control of the external parameters. The persistent currents in condensates are intimately related to the nucleation of quantized vortices, which are topological defects as response to transference of quanta of angular momentum. A conventional method for generation of such defects consists in confining the condensed atomic cloud into a rotating trap. It turns out that, for angular velocities higher than a critical value, vortex states become energetically favorable, thus inducing the creation of quantized vortices. Experimental realizations of condensed alkali-metal atoms confined by more general time-dependent potentials allowed the observation not only of vortex lattices but also of quantum turbulence. Since quantum turbulence is characterized by the presence of a self-interacting tangle of quantized vortices, the correct understanding of dynamics, formation, and stability of vortices has shown to be of paramount importance being the subject of many theoretical works. In particular, the role of acoustic excitations generated by decaying multi-charged vortices in the development of turbulence is still an open question. This work aims to provide a set of tools that helps to identify the presence as well as the charge of vortices in non-turbulent clouds observed using time-of-flight pictures. We have done a detailed study of condensates containing multi-charged vortices placed at its center where time-of-flight dynamics is only one point of our interest. Due to the control that this system provides experimentally, the collective modes become an important description since they can be excited using well stablished experimental methods as such as modulation of the s-wave scattering length, and they can also be responsible to vortex decaying. For such purposes we have used the semi-analytical variational method, and the fully numerical calculation of Gross-Pitaevskii equation. Thus we have describes the collective modes that couples dynamics of vortex with the oscillation of external components of condensed atomic cloud as well as the effects in time-of-flight. The angular momentum acts increasing the kinetic energy around the vortex core, which results in a faster expansion of perpendicular direction to it. This situation shifts the frequencies of collective oscillations of a vortex-free state, and generates richer collective modes due the coupling. Now there are four possible modes, being two types of monopole mode and two types of quadrupole modes. The difference among these types is the phase of vortex oscillation. When one considers fluctuations without polar symmetry, their collective modes result in the vortex decaying. In order to control and prevent these processes we have proposed three dynamical mechanisms such as modulation of s-wave scattering length, modulation of frequencies of harmonic trap, and modulation of the amplitude of Laguerre-Gauss potential. The last one has proven to be more effective.
Henn, Emanuel Alves de Lima. "Produção experimental de excitações topológicas em um condensado de Bose-Einstein." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/76/76131/tde-18082008-150413/.
Повний текст джерелаIn this work we describe the production and investigation of topological excitations in a Bose-Einstein condensate in Rubidium-87 atoms. The condensate is produced through forced evaporative cooling by radio-frequency in a QUIC-type purely magnetic trap. The magnetic trap is loaded from a double-MOT system. Transition temperature is about 150nK. Pure condensates containing 1-2×105 87Rb atoms are observed. We performed the characterization of the sample in relation to its fundamental aspects. Condensed fraction, anisotropic expansion, spacial distribution and finite temperature effects are described. Aiming to observe coherent topological excitations of the condensate between two states of the trap, we added a spherical quadrupole magnetic fields oscillating in time. We observe, instead, angular momentum tranference to the sample and the formation of vortices and arrays of vortices. We define amplitude regions where an increasing number of vortices are observed. We observe the formation of non-usual three-vortex structures from which we infer the existence of vortices and anti-vortices together in the sample. We observe evidence of quantum turbulence, a state where non-regular vortex arrays appear as well as vortex lines have no preferred direction to form.
Boughdad, Omar. "Fluides de lumière dans un milieu non-linéaire photoréfractif." Thesis, Université Côte d'Azur, 2020. http://www.theses.fr/2020COAZ4014.
Повний текст джерелаThis thesis presents an experimental study of hydrodynamical phenomena of a laser propagating nonlinearly. For a medium presenting an intensity-dependent refractive index, and in the frame of the paraxial approximation, The intensity of the laser beam is equivalent to a density of a fluid, the propagation direction is seen as a time evolution of the fluid as well as the phase gradient of the laser beam defines a flow velocity and the nonlinear refractive index change allows defining a sound velocity of the fluid. Under this analogy, we call the propagating laser beam a fluid of light. In this thesis, we provide a study of the superfluidity concept of a fluid of light in a selfdefocusing regime of the nonlinearity. It is defined as the absence of diffraction when the fluid of light encounters an obstacle. The parameters which control the superfluid transition are: the flow velocity as well as the sound velocity. They are controlled respectively through the wave vector and the intensity of the laser beam. In the frame of this analogy, we also present in this thesis a study of vortex shedding regime as a result of the interaction between the fluid of light and the obstacle. Here, the obstacle is considered to be strong. When twice the flow velocity at the poles of the obstacle is larger than the sound velocity, pairs of vortex/anti-vortex are emitted demonstrating a hydrodynamical behaviour of the fluid of light. In order to underline the nonlinear refractive index change, we also report in this thesis a study of the photorefractive effect using the self-phase modulation effect
HSU, MING-HOUNG, and 徐銘宏. "The Quantum Fluid Theory of Potential Scattering - Streamlines and Vortices." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/08353538059880252970.
Повний текст джерелаKonstadopoulou, Anastasia, J. M. Hollingworth, M. Everitt, Apostolos Vourdas, T. D. Clark, and J. F. Ralph. "Vortices in Josephson arrays interacting with non-classical microwaves: The effect of dissipation." 2003. http://hdl.handle.net/10454/3769.
Повний текст джерелаVortices circulating in a ring made from a Josephson array in the insulating phase are studied. The ring contains a `dual Josephson junction' through which the vortices tunnel. External non-classical microwaves are coupled to the device. The time evolution of this two-mode fully quantum mechanical system is studied, taking into account the dissipation in the system. The effect of the quantum statistics of the photons on the quantum statistics of the vortices is discussed. Entropic calculations quantify the entanglement between the two systems. Quantum phenomena in the system are also studied through Wigner functions. After a certain time (which depends on the dissipation parameters) these quantum phenomena are destroyed due to dissipation.
Chou, Chia-Chun. "Analytical study of complex quantum trajectories." Thesis, 2009. http://hdl.handle.net/2152/ETD-UT-2009-05-36.
Повний текст джерелаtext
Moyaerts, Laurent [Verfasser]. "A numerical study of quantum forces : Casimir effect, vortices and Coulomb gauge Yang-Mills theory / vorgelegt von Laurent Moyaerts." 2004. http://d-nb.info/973136820/34.
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