Segui questo link per vedere altri tipi di pubblicazioni sul tema: Casimir effect.
Tesi sul tema "Casimir effect"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Vedi i top-50 saggi (tesi di laurea o di dottorato) per l'attività di ricerca sul tema "Casimir effect".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Vedi le tesi di molte aree scientifiche e compila una bibliografia corretta.
1
Lang, Andrew. "The casimir effect /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9904856.
Testo completo
2
Holmes, Christopher David. "Acoustic Casimir effect." Monterey, California. Naval Postgraduate School, 1997. http://hdl.handle.net/10945/7844.
Testo completoAbstract (sommario):
In 1948, Hendrick Brugt Gerhard Casimir predicted that two closely spaced uncharged conducting plates in vacuum would be mutually attracted. This attractive force is an indirect manifestation of the quantum electromagnetic zero point field (ZPF). When the indirect manifestations of the ZPF are interpreted as due to radiation pressure, acoustic noise can provide an excellent analog to investigate the Casimir effect as well as other effects due to the ZPF. Force measurements between two parallel plates are performed in an acoustic chamber with a broadband noise spectrum within a 5-15 kHz band and an intensity of 133 dB (re 20 %Pa). When the results are compared with the appropriate theory, very good agreement is obtained. Applications of the acoustic Casimir effect to noise transduction can provide new means to measure background noise. Because attractive or repulsive forces can be obtained by adjusting the noise spectrum or the plate geometry, a non-resonant method of acoustic levitation is also suggested
3
Jacobs, David M. "Casimir Localization." Case Western Reserve University School of Graduate Studies / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=case1396608069.
Testo completo
4
Rypestøl, Marianne. "Casimir effect in Randall-Sundrummodels." Thesis, Norwegian University of Science and Technology, Department of Physics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-6353.
Testo completo
5
Noto, Antonio. "Non-equilibrium Casimir interactions : from dynamical to thermal effects." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT279/document.
Testo completoAbstract (sommario):
Dans cette thèse, après une introduction où nous présentons brièvement la physique des forces de Casimir, nous montrons nos résultats obtenus pendant le doctorat. D'abord, nous montrons notre travail sur les interactions de van der Waals / Casimir-Polder lorsque le système est dans une configuration hors équilibre à cause du mouvement uniformément accéléré des atomes. Nous étudions le système de deux atomes uniformément accélérés dans le vide quantique quand ils sont dans leur état fondamental ou dans un état corrélé (un atome excité et un atome dans son état fondamental). Nous analysons ce système avec un modèle heuristique semi-classique et une méthode plus rigoureuse qui nous avons étendu à partir d'une procédure générale développée dans la littérature. Nous trouvons un changement de la dépendance de l'interaction de la distance en raison de l'accélération. Nous montrons que les forces de Casimir-Polder entre deux atomes uniformément accélérés en mouvement relativiste, qui interagissent avec le champ scalaire, présentent une transition à partir d'un comportement thermique à courtes distances, comme prédit par l'effet Unruh, à un comportement non thermique à longues distances, associé à la rupture de la description inertielle et locale du système. En plus, lorsque le cas d'atomes qui interagissent avec le champ électromagnétique quantique est considéré, on constate que de nouvelles caractéristiques apparaissent dans l'interaction.Ensuite, nous présentons notre travail sur un nouveau couplage opto-mécanique d'un miroir oscillant de façon efficace avec un gaz d'atomes de Rydberg, médié par la force atome-miroir dynamique de Casimir-Polder. Nous constatons que ce couplage peut produire une excitation de résonance atomique de champ proche, qui n'est pas liée à l'excitation des atomes par les quelques photons réels attendus de l'effet Casimir dynamique. Dans des conditions expérimentales accessibles, cette probabilité d'excitation est importante (environ 20 %) et rend possible l'observation de ce nouvel effet Casimir-Polder dynamique. Donc nous proposons une configuration expérimentale réaliste pour réaliser ce système fait d'un gaz d'atomes froids piégés mis en face d'un substrat semi-conducteur, dont les propriétés diélectriques sont modulées dans le temps.Enfin, nous nous concentrons sur nos résultats obtenus pour le calcul de la pression Casimir-Lifshitz entre deux réseaux lamellaires diélectriques différents. Ce système est supposé dans une configuration hors équilibre thermique. En fait, les deux réseaux présentent deux températures différentes et ils sont immergés dans un bain thermique ayant une troisième température. Le calcul de la pression est basé sur une méthode qui exploite les opérateurs de diffusion des réseaux, déduits en utilisant la méthode modale de Fourier. Nous présentons nos résultats numériques caractérisant en détail le comportement de la pression, en faisant varier les trois températures et en modifiant les paramètres géométriques des réseaux. Cette variation des paramètres du système permet de régler la force de répulsive à attractive ou de réduire fortement la pression pour des intervalles de températures. En outre, on montre que la combinaison des effets de non-équilibre et géométriques rend ce système particulièrement intéressant pour l'observation de la force de Casimir répulsive<br>In this thesis, after an introduction where we briefly present the general context of Casimir physics, we present the results obtained during the PhD. At first, we show our work about the van der Waals/Casimir-Polder interactions between two atoms in an out-of-equilibrium condition due to their uniformly accelerated motion. We study the system of two uniformly accelerated atoms in vacuum space, when they are in their ground-state and when they are in a correlated state (one excited and one ground-state atom). We analyze this system both with an heuristic semiclassical model and with a more rigorous method, based on a separation of radiation reaction and vacuum fluctuations contributions, that we extend starting from a general procedure known in literature. We find a change of the distance-dependence of the interaction due to the acceleration. We show that Casimir-Polder forces between two relativistic uniformly accelerated atoms, interacting with the scalar field, exhibit a transition from the short-distance thermal-like behavior predicted by the Unruh effect to a long-distance nonthermal behavior, associated with the breakdown of a local inertial description of the system. In addition, we obtain new features of the resonance interaction in the case of atoms interacting with the quantum electromagnetic field.Next, we present our work about a new optomechanical coupling of an effectively oscillating mirror with a Rydberg atoms gas, mediated by the dynamical atom-mirror Casimir-Polder force. We find that this coupling may produce a near-field resonant atomic excitation not related to the excitation of atoms by the few real photons expected by dynamical Casimir effect. In accessible experimental conditions, this excitation probability is significant (about 20%) making the observation of this new dynamical Casimir-Polder effect possible. For this reason, we propose a realistic experimental configuration to realize this system made of a cold atom gas trapped in front of a semiconductor substrate, whose dielectric properties are periodically modulated in time.Finally, we focus on our results obtained for the Casimir-Lifshitz pressure between two different dielectric lamellar gratings. This system is assumed to be in an out-of-thermal-equilibrium configuration, i.e. the two gratings have two different temperatures and they are immersed in a thermal bath having a third temperature. The computation of the pressure is based on a method exploiting the scattering operators of the bodies, deduced using the Fourier modal method. In our numerical results we characterize in detail the behavior of the pressure, both by varying the three temperatures and by changing the geometrical parameters of the gratings. In this way we show that it is possible to tune the force from attractive to repulsive or to strongly reduce the pressure for large ranges of temperatures. Moreover, we stress that the interplay between nonequilibrium effects and geometrical periodicity make this system particularly interesting for the observation of the repulsive Casimir force
6
Haakh, Harald Richard. "Cavity QED with superconductors and its application to the Casimir effect." Master's thesis, Universität Potsdam, 2009. http://opus.kobv.de/ubp/volltexte/2009/3256/.
Testo completoAbstract (sommario):
Diese Diplomarbeit untersucht den Casimir-Effekt zwischen normal- und supraleitenden Platten über einen weiten Temperaturbereich, sowie die Casimir-Polder-Wechselwirkung zwischen einem Atom und einer solchen Oberfläche. Hierzu wurden vorwiegend numerische und asymptotische Rechnungen durchgeführt. Die optischen Eigenschaften der Oberflächen werden dann aus dielektrischen Funktionen oder optischen Leitfähigkeiten erhalten.
Wichtige Modellen werden vorgestellt und insbesondere im Hinblick auf ihre analytischen und kausalen Eigenschaften untersucht.
Es wird vorgestellt, wie sich die Casimir-Energie zwischen zwei normalleitenden Platten berechnen lässt. Frühere Arbeiten über den in allen metallischen Kavitäten vorhandenen Beitrag von Oberflächenplasmonen zur Casimir-Wechselwirkung wurden zum ersten mal auf endliche Temperaturen erweitert. Für Supraleiter wird eine analytische Fortsetzung der BCS-Leitfähigkeiten zu rein imaginären Frequenzen, sowohl innerhalb wie außerhalb des schmutzigen Grenzfalles verschwindender mittlerer freier Weglänge vorgestellt. Es wird gezeigt, dass die aus dieser neuen Beschreibung erhaltene freie Casimir-Energie in bestimmten Bereichen der Materialparameter hervorragend mit der im Rahmen des Zwei-Fluid-Modells für den Supraleiter berechneten übereinstimmt. Die Casimir-Entropie einer supraleitenden Kavität erfüllt den Nernstschen Wärmesatz und weist einen charakteristischen Sprung beim Erreichen des supraleitenden Phasenübergangs auf. Diese Effekte treten ebenfalls in der magnetischen Casimir-Polder-Wechselwirkung eines Atoms mit einer supraleitenden Oberfläche auf.
Es wird ferner gezeigt, dass die magnetische Dipol-Wechselwirkung eines Atomes mit einem Metall sehr stark von den dissipativen Eigenschaften und insbesondere von den Oberflächenströmen abhängt. Dies führt zu einer starken Unterdrückung der magnetischen Casimir-Polder-Energie bei endlichen Temperaturen und Abständen oberhalb der thermischen Wellenlänge. Die Casimir-Polder-Entropie verletzt in einigen Modellen den Nernstschen Wärmesatz.Ähnliche Effekte werden für den Casimir-Effekt zwischen Platten kontrovers diskutiert. In den entsprechenden elektrischen Dipol-Wechselwirkungen tritt keiner dieser Effekte auf.
Die Ergebnisse dieser Arbeit legen nahe, das bekannte Plasma-Modells als Grenzfall eines Supraleiters bei niedrigen Temperaturen (bekannt als London-Theorie) zu betrachten, statt als Beschreibung eines normales Metalles.
Supraleiter bieten die Möglichkeit, die Dissipation der Oberflächenströme in hohem Maße zu steuern. Dies könnte einen experimentellen Zugang zu den optischen Eigenschaften von Metallen bei niedrigen Frequenzen erlauben, die eng mit dem thermischen Casimir-Effekt verknüpft sind. Anders als in entsprechenden Mikrowellen-Experimenten sind hierbei die Energien und Impulse unabhängige Größen. Die Messung der Oberflächenwechselwirkung zwischen Atomen und Supraleitern ist mit den heute verfügbaren Atomfallen auf Mikrochips möglich und der magnetische Anteil der Wechselwirkung sollte spektroskopischen Techniken zugänglich sein<br>This thesis investigates the Casimir effect between plates made of normal and superconducting metals over a broad range of temperatures, as well as the Casimir-Polder interaction of an atom to such a surface. Numerical and asymptotical calculations have been the main tools in order to do so. The optical properties of the surfaces are described by dielectric functions or optical conductivities, which are reviewed for common models and have been analyzed with special weight on distributional properties and causality.
The calculation of the Casimir energy between two normally conducting plates (cavity) is reviewed and previous work on the contribution to the Casimir energy due to the surface plasmons, present in all metallic cavities, has been generalized to finite temperatures for the first time. In the field of superconductivity, a new analytical continuation of the BCS conductivity to to purely imaginary frequencies has been obtained both inside and outside the extremely dirty limit of vanishing mean free path. The Casimir free energy calculated from this description was shown to coincide well with the values obtained from the two fluid model of superconductivity in certain regimes of the material parameters. The Casimir entropy in a superconducting cavity fulfills the third law of thermodynamics and features a characteristic discontinuity at the phase transition temperature. These effects were equally encountered in the Casimir-Polder interaction of an atom with a superconducting wall.
The magnetic dipole coupling of an atom to a metal was shown to be highly sensible to dissipation and especially to the surface currents. This leads to a strong quenching of the magnetic Casimir-Polder energy at finite temperature.
Violations of the third law of thermodynamics are encountered in special models, similar to phenomena in the Casimir-effect between two plates, that are debated controversely. None of these effects occurs in the analog electric dipole interaction.
The results of this work suggest to reestablish the well-known plasma model as the low temperature limit of a superconductor as in London theory rather than use it for the description of normal metals. Superconductors offer the opportunity to control the dissipation of surface currents to a great extent. This could be used to access experimentally the low frequency optical response of metals, which is strongly connected to the thermal Casimir-effect.
Here, differently from corresponding microwave experiments, energy and momentum are independent quantities.
A measurement of the total Casimir-Polder interaction of atoms with superconductors seems to be in reach in today’s microchip-based atom-traps and the contribution due to magnetic coupling might be accessed by spectroscopic techniques
7
Hassan, Arkan Mahmood. "Dynamical Casimir Effect Using Two Photon Absorber." Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1533948476369766.
Testo completo
8
van, Caspel Moos. "The topological Casimir effect on a torus." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44948.
Testo completoAbstract (sommario):
The conventional Casimir effect manifests itself as a quantum mechanical force between two plates, that arises from the quantization of the electromagnetic field in the enclosed vacuum. In this thesis the existence is discussed of an extra, topological term in the Casimir energy at finite temperatures. This topological Casimir effect emerges due to the nontrivial topological features of the gauge theory: the extra energy is the result of tunneling transitions between states that are physically the same but topologically distinct. It becomes apparent when examining, for instance, periodic boundary conditions. I explicitly calculate the new term for the simplest example of such a system, a Euclidean 4-torus. By dimensional reduction, this system is closely related to two dimensional electromagnetism on a torus, which is well understood. It turns out that the topological term is extremely small compared to the conventional Casimir energy, but that the effect is very sensitive to an external magnetic field. The external field plays the role of a topological theta parameter, analogous to the theta vacuum in Yang-Mills theory. The topological Casimir pressure and the induced magnetic field show a distinctive oscillation as a function of the external field strength, something that can hopefully be observed experimentally.
9
McCutcheon, Robert A. "Hybrid Optomechanics and the Dynamical Casimir Effect." Miami University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=miami1501191323617929.
Testo completo
10
Fialkovskiy, Ignat. "Efeito Casimir e as propriedades óticas do grapheno." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-11032013-151501/.
Testo completoAbstract (sommario):
Este trabalho é dedicado à investigação de diferentes aspectos da física de monocamadas de grafeno suspenso e epitaxial. A descrição do grafeno é baseada no modelo quase-relativístico de Dirac. Isso permite a aplicação dos métodos da Teoria Quântica de Campos (TQC) na investigação dos efeitos de interação entre o grafeno e o campo eletromagnético (EM). Usando o formalismo de integral de trajetória, nós formulamos uma teoria efetiva do campo EM na presença de monocamadas de grafeno. Esta teoria é governada pelo operador de polarização das quase-partículas de Dirac. Dois fenômenos importantes são investigados: as propriedades óticas do grafeno (o efeito Faraday em particular) e a interação de Casimir entre uma camada de grafeno e um metal paralelo. Em primeiro lugar, estudamos a propagação de ondas eletromagnéticas na presença de camadas de grafeno. A dinâmica de ondas é governada pelas equações modificadas de Maxwell obtidas a partir da teoria efetiva para o campo EM. Nós calculamos os coeficientes de reflexão e transmissão de luz polarizada linearmente e investigamos detalhadamente o efeito quântico de Faraday no campo magnético externo. Em particular, mostramos que as previsões do modelo de Dirac estão em boa concordância com os recentes resultados experimentais sobre a transmissão de luz e rotação de Faraday gigante em regime de ressonância cíclotron. Novos regimes também são previstos. Em segundo lugar, investigamos a interação de Casimir entre filmes suspensos de grafeno com um condutor ideal. O efeito é investigado tanto no caso ideal (temperatura nula, amostras ideais) quanto para configurações mais realistas (temperatura não nula e a presença de potencial químico). No caso de temperatura nula, a força de Casimir entre grafeno e condutor ideal é aproximadamente 2.6% da força entre dois condutores ideais. Ao mesmo tempo, no limite de temperatura elevada, o efeito mostra-se ser muito forte cerca de 50% de efeito entre metais ideais.<br>This research is devoted to investigation of several aspects of the physics of suspended and epitaxial graphene monolayers. The description of graphene is based on the quasi--relativistic Dirac model which permits application of the methods of the Quantum Field Theory to investigation of the interaction of graphene with electromagnetic field. Basing on the path integral formalism we formulate the effective theory for EM field in presence of graphene monolayers which is governed by the polarization operator of the Dirac quasi-particles in graphene. The two main phenomena in the interaction of graphene with electromagnetic field are studied: the optical properties of graphene (the Faraday rotation in particular), and Casimir interaction between graphene samples and parallel metal. First, we study the propagation of electromagnetic waves in presence of suspended and epitaxial graphene layers. Their dynamics is governed by the modified Maxwell equations obtained from the effective theory for EM field. We calculate the reflection and transmission coefficient for linearly polarized light and investigate in detail the quantum Faraday effect in external magnetic field. In particular it is showed that the prediction of the Dirac model are in good agreement with recent experimental results on transmission and giant Faraday rotation in cyclotron resonance. New regimes are also predicted Secondly, we investigate Casimir interaction between suspended graphene films with ideal conductor. The effect is investigated both in the idealistic case (zero temperature, ideal samples) and for realistic configurations (non zero temperature and/or presence of impurities and chemical potential). For zero temperature the Casimir force between graphene and a conductor is about 2.7% of that between two ideal conductors. At the same time in the high temperature limit the effect is showed to be greatly enhanced being about 50% of that between ideal metals.
11
Mackrory, Jonathan. "The Worldline Method for Electromagnetic Casimir Energies." Thesis, University of Oregon, 2017. http://hdl.handle.net/1794/22664.
Testo completoAbstract (sommario):
The Casimir effect refers to the primarily attractive force between material bodies due to quantum fluctuations in the electromagnetic field. The Casimir effect is difficult to calculate in general, since it is sensitive to the exact shapes of the bodies and involves contributions from all frequencies. As a result, calculating the Casimir effect between general bodies usually requires a numerical approach. The worldline method computes Casimir energies by creating an ensemble of space-time paths corresponding to a virtual particle interacting with the bodies. This method was originally developed for a scalar fields coupled to an idealized background potential, rather than the vector electromagnetic field interacting with media.
This thesis presents work on extending the worldline method to account for the material properties of the interacting bodies, and the polarizations of electromagnetism. This thesis starts by covering background material on path integrals, and quantizing the electromagnetic field in media. The electromagnetic field is decomposed in terms of two scalar fields for planar bodies, where these scalar fields correspond to the transverse-electric and transverse-magnetic polarizations of the electromagnetic field. The worldline path integrals are developed for both polarizations, and solved analytically. Next, numerical methods are developed and tested in the context of planar bodies. The starting positions, and scale of the paths, and shape of the paths are sampled via Monte Carlo methods. The transverse-magnetic path integral also requires specialized methods for estimating derivatives, and path construction. The analytical and numerical results for both worldline path integrals are in agreement with known solutions. Finally, specialized methods are developed for computing derivatives of the worldline Casimir-energy path integrals,
allowing for efficient numerical computations of Casimir forces and torques.
12
Cho, Sung Nae. "Casimir Force in Non-Planar Geometric Configurations." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/11156.
Testo completoAbstract (sommario):
The Casimir force for charge-neutral, perfect conductors of non-planar geometric configurations have been investigated. The configurations were: (1) the plate-hemisphere, (2) the hemisphere-hemisphere and (3) the spherical shell. The resulting Casimir forces for these physical arrangements have been found to be attractive. The repulsive Casimir force found by Boyer for a spherical shell is a special case requiring stringent material property of the sphere, as well as the specific boundary conditions for the wave modes inside and outside of the sphere. The necessary criteria in detecting Boyer's repulsive Casimir force for a sphere are discussed at the end of this thesis.<br>Ph. D.
13
Le, Cunuder Anne. "Étude expérimentale des forces de Casimir." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEN007/document.
Testo completoAbstract (sommario):
L'étude des fluctuations dans les milieux confinés constitue un domaine de recherche très récent, que ce soit du point de vue théorique ou expérimental. Afin d'analyser le rôle du confinement sur les propriétés des fluctuations de densité dans un mélange binaire, nous avons développé un système de mesure d'une grande sensibilité, où l'intensité des fluctuations et leur longueur de corrélation peuvent être amplifiées. L'idée consiste à travailler proche du point critique d'une transition de phase de démixion d'un mélange binaire. En effet, la longueur de corrélation augmente exponentiellement lorsqu'on s'approche de la température Tc du point critique de démixion.Nous avons développé un montage permettant de confiner le mélange entre un échantillon plan et une sphère colloïdale attachée à l'extrémité d'un levier de Microscope à Force Atomique (AFM). D'après les prédictions de Fisher et De Gennes, un effet intéressant émerge lorsque la longueur de corrélation est comparable avec la taille du confinement: les deux surfaces vont soit s'attirer, soit se repousser suivant les préférences d'adsorption des composants du mélange pour chacune des surfaces. On nomme cet effet l'effet Casimir critique, en référence à la force de Casimir électrodynamique qui résulte du confinement des fluctuations quantiques du champ électromagnétique.Durant cette thèse, nous avons mesuré la force de Casimir électrodynamique avec le système de mesure que nous avons développé, d'abord dans une atmosphère d'azote puis dans l'éthanol. Ces mesures prouvent que notre appareil de mesure est assez sensible pour mesurer des forces très faibles de l'ordre de la dizaine de pN. Les forces mesurées sont comparées à la théorie de Lifshitz, où les effets de conductivité finie des surfaces sont considérées<br>The study of density fluctuations inside confined liquid systems has received the attention of recent theoretical and experimental papers. In order to analyze the role of confinement on the statistical properties of fluctuations, we developed a highly sensitive system where the intensity of fluctuations, as well as their spatial correlation length can be simply tuned. The idea will be to enhance the role of fluctuations working close to the critical temperature Tc of a second order phase transition in a binary mixture. Indeed, the correlation length dramatically increases when one approaches the critical demixion point.The confinement is obtained by using a sphere-plane geometry with a colloidal particle attached to the cantilever of an Atomic Force Microscope (AFM). When the correlation length is comparable with the distance of confinement, Fisher and De Gennes predicted the existence of an interesting effect: the two surfaces will be submitted to either an attracting or a repelling force, depending on boundary conditions. This effect is called the critical Casimir force in reference to the quantum Casimir force resulting from the confinement of quantum fluctuations of the electromagnetic field.During this thesis, we measured the quantum Casimir force between the sphere and the plate, first in a nitrogen atmosphere and then in ethanol, showing that the developed instrument is sufficiently sensible to measure very weak force, of the same order of magnitude or even weaker than the critical Casimir force. Measurements are compared to Lifshitz theory, taking into account the finite conductivity of surfaces
14
Azari, Arash. "Casimir effect in presence of dielectric and metallic materials." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531132.
Testo completo
15
Klatt, Juliane [Verfasser], and Stefan Yoshi [Akademischer Betreuer] Buhmann. "The Casimir-Polder effect and quantum friction across timescales." Freiburg : Universität, 2017. http://d-nb.info/115468184X/34.
Testo completo
16
Messineo, Giuseppe. "The MIR experiment: quantum vacuum and dynamical Casimir effect." Doctoral thesis, Università degli studi di Trieste, 2011. http://hdl.handle.net/10077/4572.
Testo completoAbstract (sommario):
2009/2010<br>This thesis concerns one of the few low energy experimental efforts aiming to test Quantum Electrodynamics. The experiment MIR (Motion Induced Radiation) studies the quantum vacuum in the presence of accelerated boundaries. According to Quantum Electrodynamics, a non-uniformly accelerated mirror in vacuum feels a friction force due to the interaction with the vacuum photons. As a consequence, real photons are produced in the process, which is known as dynamical Casimir effect. The radiated energy is emitted at the expense of the mechanical energy of the mirror. The effect has never been observed experimentally, since it is very feeble. Only recently a few experimental approaches have been proposed.
The theory of the dynamical Casimir effect has been treated extensively in literature. According to the models proposed, for harmonic oscillations the effect is proportional to the oscillation frequency. As all the papers refer to frequencies of the order of a gigahertz, it is not possible to tackle the problem of obtaining a moving boundary with a purely mechanical approach, for example employing piezoelectric transducers or acoustic excitations, due to the large amount of energy required to keep a massive object in motion. A solution to this problem was proposed at the end of the 80's and has been adopted in the MIR experiment. In this framework the moving boundary is a semiconductor slab that switches periodically from complete transparency to total reflection when illuminated by a train of laser pulses. In this way one obtains a time variable mirror which mimics a physical oscillation, without the burden of overcoming the inertia of the mirror.
Even so, the number of photons expected is extremely small. The MIR experimental strategy to enhance the photon production is to have the mirror as the wall of a resonating cavity. In this case, if the repetition rate of the laser is about twice a resonance frequency of the cavity, a parametric amplification process occurs, resulting in an enhancement of the number of photons by a factor which depends on the Q-value of the cavity. To this end, superconducting cavities are employed in the experiment.<br>Questa tesi riguarda uno dei pochi esperimenti di bassa energia dedicati allo studio dell'Elettrodinamica Quantistica. L'esperimento MIR (Motion Induced Radiation) studia il vuoto quantistico in presenza di condizioni al contorno accelerate. Secondo l'Elettrodinamica Quantistica, uno specchio non uniformemente accelerato nel vuoto risente di una forza di attrito dovuta all'interazione con i fotoni del vuoto. In conseguenza di ciò in questo processo, noto come effetto Casimir dinamico, vi è produzione di fotoni reali. L'energia irradiata viene emessa a scapito dell'energia meccanica dello specchio. L'effetto è molto debole e non è mai stato osservato sperimentalmente.
Solo di recente sono stati proposti alcuni approcci sperimentali, mentre gli aspetti teorici sono stati trattati ampiamente in letteratura. Secondo i modelli proposti, nel caso di oscillazioni armoniche l'effetto è proporzionale alla frequenza di oscillazione. Poiché tutti gli articoli fanno riferimento a frequenze dell'ordine di un gigahertz, con un approccio puramente meccanico, ad esempio impiegando trasduttori piezoelettrici o eccitazioni acustiche, non è possibile risolvere il problema di ottenere uno specchio in movimento a causa della grande quantità di energia richiesta per mantenere un oggetto massivo in moto.
Una soluzione a questo problema è stata proposta alla fine degli anni '80 ed è stata adottata nell'esperimento MIR. L'idea è che la parete in movimento possa essere sostituita da un lastra di semiconduttore che periodicamente passa da uno stato di totale trasparenza ad uno di alta riflettività, per illuminazione da parte di un treno di impulsi laser. In tal modo è possibile ottenere un specchio variabile nel tempo che riproduce una oscillazione fisica, senza la necessità di superare l'inerzia dello specchio.
Anche in questo caso tuttavia, il numero di fotoni previsto è estremamente ridotto. La strategia sperimentale di MIR per aumentare la produzione di fotoni è quella di utilizzare lo specchio variabile come parete di una cavità risonante. Se la frequenza di ripetizione del laser è circa due volte la frequenza di risonanza della cavità, si verifica un processo di amplificazione parametrica, con un conseguente aumento del numero di fotoni prodotti. Poiché questo incremento dipende dal Q-valore della cavità, nell'esperimento vengono impiegate cavità superconduttrici.<br>XXIII Ciclo<br>1980
17
Woolf, David Nathaniel. "Near-Field Optical Forces: Photonics, Plasmonics and the Casimir Effect." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10812.
Testo completoAbstract (sommario):
The coupling of macroscopic objects via the optical near-field can generate strong attractive and repulsive forces. Here, I explore the static and dynamic optomechanical interactions that take place in a geometry consisting of a silicon nanomembrane patterned with a square-lattice photonic crystal suspended above a silicon-on-insulator substrate. This geometry supports a hybridized optical mode formed by the coupling of eigenmodes of the membrane and the silicon substrate layer. This system is capable of generating nanometer-scale deflections at low optical powers for membrane-substrate gaps of less than 200 nm due to the presence of an optical cavity created by the photonic crystal that enhances both the optical force and a force that arises from photo-thermal-mechanical properties of the system. Feedback between Brownian motion of the membrane and the optical and photo-thermal forces lead to dynamic interactions that perturb the mechanical frequency and linewidth in a process known as ``back-action.'' The static and dynamic properties of this system are responsible for optical bistability, mechanical cooling and regenerative oscillations under different initial conditions. Furthermore, solid objects separated by a small distance experience the Casimir force, which results from quantum fluctuations of the electromagnetic field (i.e. virtual photons).The Casimir force supplies a strong nonlinear perturbation to membrane motion when the membrane-substrate separation is less than 150 nm. Taken together, the unique properties of this system makes it an intriguing candidate for transduction, accelerometry, and sensing applications.<br>Engineering and Applied Sciences
18
Scardicchio, Antonello. "An optical approximation to the Casimir effect and related topics." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/36811.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.<br>Includes bibliographical references (leaves 181-188).<br>In this thesis, I have studied the dependence of the Casimir force between neutral conductors on their shapes. After reducing the problem to that of finding the density of states of' an appropriate hamiltonian I studied it by using semiclassical methods. Some exemplary geometries of interest for the experiments are studied in detail.<br>by Antonello Scardicchio.<br>Ph.D.
19
NOSARI, GABRIELE. "Local approach to Casimir effect in axiomatic quantum field theory." Doctoral thesis, Università degli studi di Pavia, 2017. http://hdl.handle.net/11571/1203292.
Testo completo
20
Borjan, Zoran. "Application of local functional theory to surface critical phenomena." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302201.
Testo completo
21
Obousy, Richard K. Cleaver Gerald B. "Investigation into compactifed dimensions Casimir energies and phenomenological aspects /." Waco, Tex. : Baylor University, 2008. http://hdl.handle.net/2104/5261.
Testo completo
22
Ghadirian, Bahman. "A new regularization procedure for calculating the Casimir energy." Thesis, View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/24942.
Testo completoAbstract (sommario):
This thesis deals with the concepts of a very interesting phenomenon in quantum physics, the Casimir effect. Here the effect is investigated in detail and its importance to other areas of physics is analysed. The Casimir effect is produced by disturbing the vacuum energy when material boundaries or background fields are introduced in the vacuum. The usual approach to this effect is the vacuum fluctuation that has been studied in the past in relation to the discussion of the zero-point energy as a result of the field resemblance to the quantum harmonic oscillators, where residual ground state energy must be considered. In this thesis a new method to study vacuum fluctuations is presented. This new approach to the problem which is more classical is based on the Heisenberg uncertainty principle and the very important fluctuation-dissipation theorem. The other aim of the thesis is to implement a new algorithm for regularizing the Casimir energy for a massive scalar field. Unlike the previous works on this problem by other authors that give approximate results, this attempt will produce precise results. My method is based on a new regularization procedure that allows us to employ the very reliable dimensional regularization scheme in place of a more mathematically complicated zeta-function regularization procedure. In order to achieve this goal I will deal with the problem by using the Euler-Maclaurin summation formula. The result will be a regularized Casimir energy for the case of a massive scalar field. This model may be used for the other geometrical boundaries and different fields.
23
Colombaro, Ivano. "Dynamical Casimir effect and the structure of vacuum in quantum field theory." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10382/.
Testo completoAbstract (sommario):
Some of the most interesting phenomena that arise from the developments of the modern physics are surely vacuum fluctuations. They appear in different branches of physics, such as Quantum Field Theory, Cosmology, Condensed Matter Physics, Atomic and Molecular Physics, and also in Mathematical Physics.
One of the most important of these vacuum fluctuations, sometimes called "zero-point energy", as well as one of the easiest quantum effect to detect, is the so-called Casimir effect.
The purposes of this thesis are:
- To propose a simple retarded approach for dynamical Casimir effect, thus a description of this vacuum effect when we have moving boundaries.
- To describe the behaviour of the force acting on a boundary, due to its self-interaction with the vacuum.
24
Ghadirian, Bahman. "A new regularization procedure for calculating the Casimir energy." View thesis, 2008. http://handle.uws.edu.au:8081/1959.7/24942.
Testo completoAbstract (sommario):
Thesis (Ph.D.)--University of Western Sydney, 2008.<br>A thesis submitted to the University of Western Sydney, College of Health and Science, School of Biomedical and Health Sciences in fulfilment of the requirements for the degree of Doctor of Philosophy. Includes bibliographical references.
25
Мороз, Ю. В. "Вперше виміряна сила відштовхування в ефекті Казимира-Ліфшиця". Thesis, Сумський державний університет, 2013. http://essuir.sumdu.edu.ua/handle/123456789/41113.
Testo completoAbstract (sommario):
Квантова механіка пророкує, що на відстанях порядку нанометра
між тілами повинна спостерігатися сила тяжіння, яка за своїми
параметрами відмінна від сили всесвітнього тяжіння Ньютона. Таке
явище називають ефектом Казимира. Крім того при певних умовах
тяжіння тіл може змінитися на їх відштовхування. В такому випадку
говорять про об'єднаний ефект Казимира-Лифшиця.
26
Canaguier-Durand, Antoine. "Multipolar scattering expansion for the Casimir effect in the sphere-plane geometry." Paris 6, 2011. http://www.theses.fr/2011PA066246.
Testo completoAbstract (sommario):
Nous évaluons l’interaction de Casimir entre un miroir plan et un miroir sphérique, à température arbitraire, en tenant compte de la réflexion imparfaite. Cela nous permet d’étudier la riche dépendance à la géométrie de l’effet Casimir, et d’estimer l’erreur faite par l’approximation de proximité (PFA), communément utilisée pour cette configuration sphère-plan qui est celle des expériences. Pour cette évaluation nous appliquons la méthode de diffusion, basée sur la théorie des réseaux optiques, à la géométrie sphère-plan. La température est prise en compte par la formule de Matsubara. La réflexion sur le plan est exprimée à l’aide d’ondes planes, celle sur la sphère à l’aide d’ondes sphériques, entraînant un développement multipolaire. Les indices (l,m) de ces dernières sont tronqués à une valeur maximale pour l’évaluation numérique. Nous étudions d’abord le cas de la température nulle. Les résultats numériques permettent de caractériser l’erreur des différentes méthodes d’approximation, en fonction du modèle utilisé pour les miroirs, et de mettre en évidence des corrélations entre les effets de géométrie et de conductivité finie. Nous analysons ensuite la dépendance de l’effet Casimir à la température. Pour des miroirs parfaits, nous observons des corrélations entre les effets thermiques et géométriques pouvant entraîner une contribution répulsive des photons thermiques à la force de Casimir. Ce phénomène peut être associé à l’apparition de valeurs négatives pour l’entropie. Enfin, pour des miroirs métalliques à température ambiante nous observons une grande variété de corrélations entre les effets de la géométrie, de la température et de la dissipation dans les métaux.
27
Chiu, Hsiang-Chih. "Demostration of non-additivity ans asymmetry in the lateral Casimir force." Diss., UC access only, 2009. http://proquest.umi.com/pqdweb?index=41&did=1905738741&SrchMode=1&sid=2&Fmt=7&retrieveGroup=0&VType=PQD&VInst=PROD&RQT=309&VName=PQD&TS=1270142776&clientId=48051.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of California, Riverside, 2009.<br>Includes abstract. Includes bibliographical references (leaves 146-154). Issued in print and online. Available via ProQuest Digital Dissertations.
28
Droujinina, Viola. "On quantum reflection and the Casimir effect application to atom surface scattering /." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=96859607X.
Testo completo
29
Simpson, William M. R. "Surprises in theoretical Casimir physics : quantum forces in inhomogeneous media." Thesis, University of St Andrews, 2014. http://hdl.handle.net/10023/6338.
Testo completoAbstract (sommario):
This thesis considers the problem of determining Casimir-Lifshitz forces in inhomogeneous media. The ground-state energy of the electromagnetic field in a piston-geometry is discussed. When the cavity is empty, the Casimir pressure on the piston is finite and independent of the small-scale physics of the media that compose the mirrors. However, it is demonstrated that, when the cavity is filled with an inhomogeneous dielectric medium, the Casimir energy is cut-off dependent. The local behavior of the stress tensor commonly used in calculations of Casimir forces is also determined. It is shown that the usual expression for the stress tensor is not finite anywhere within such a medium, whatever the temporal dispersion or index profile, and that this divergence is unlikely to be removed by modifying the regularisation. These findings suggest that the value of the Casimir pressure may be inextricably dependent on the detailed behavior of the mirror and the medium at large wave vectors. This thesis also examines two exceptions to this rule: first, the case of an idealised metamaterial is considered which, when introduced into a cavity, reduces the magnitude of the Casimir force. It is shown that, although the medium is inhomogeneous, it does not contribute additional scattering events but simply modifies the effective length of the cavity, so the predicted force is finite and can be stated exactly. Secondly, a geometric argument is presented for determining a Casimir stress in a spherical mirror filled with the inhomogeneous medium of Maxwell's fish-eye. This solution questions the idea that the Casimir force of a spherical mirror is repulsive, but prompts additional questions concerning regularisation and the role of non-local effects in determining Casimir forces.
30
Fermi, D. "A FUNCTIONAL ANALYTIC FRAMEWORK FOR LOCAL ZETA REGULARIZATION AND THE SCALAR CASIMIR EFFECT." Doctoral thesis, Università degli Studi di Milano, 2016. http://hdl.handle.net/2434/360961.
Testo completoAbstract (sommario):
It is developed a functional analytic framework allowing to formulate a rigorous implementation of zeta regularization for a canonically quantized scalar field, living on an arbitrary spatial domain and interacting with a classical background potential. This framework relies on the construction of an infinite scale of graded Hilbert spaces associated to the real powers of some given, positive self-adjoint operator. When the latter is a Schr\"odinger-type differential operator, this formulation provides a natural language to study the integral kernels related to a large class of operators, fulfilling minimal regularity requirements; particular attention is devoted to the regularity of these kernels and to the construction of their analytic continuations with respect to some parameters. Within this framework, complex powers of the elliptic operator giving rise to the Klein-Gordon equation are used to define a zeta-regularized version of the Wightman field whose pointwise evaluation is well-posed. This regularized field determines regularized local observables (such as the stress-energy tensor), whose vacuum expectation values can be expressed in terms of the above mentioned integral kernels. This allows to make contact with the theory of the Casimir effect. Renormalization is achieved by analytic continuation, which is proved to give finite results for the previously mentioned expectation values in most cases of interest. Finally, to exhibit the computational efficiency of the above methods, some explicit examples are discussed.
31
Maia, Clóvis Achy Soares [UNESP]. "Fluxos e densidades de energia negativa em teoria quântica de campos." Universidade Estadual Paulista (UNESP), 2005. http://hdl.handle.net/11449/91855.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-06-11T19:25:30Z (GMT). No. of bitstreams: 0
Previous issue date: 2005-03Bitstream added on 2014-06-13T20:33:11Z : No. of bitstreams: 1
maia_cas_me_ift.pdf: 968895 bytes, checksum: 0a94d217b227cfdce0aee0d507acf35f (MD5)<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>Sabe-se já há algum tempo que a Teoria Quântica de Campos permite violações das Condições Clássicas de Energia na forma de densidades e fluxos de energia negativa. Um exemplo contundente é o efeito Casimir, onde o estado de vácuo do campo eletromagnético entre duas placas metálicas possui densidade de energia negativa. Porém, se as leis da física não colocassem restrições sobre tais violações das Condições de Energia, aparentemente seria possível usar energias negativas para, por exemplo, produzir violações macroscópicas da segunda lei da termodinâmica, da conjectura de cosmic censorship, além de se proporcionar a criação de wormholes e possíveis máquinas do tempo. Uma linha de pesquisa desenvolvida para abordar essa questão envolve as chamadas Desigualdades Quânticas, estudadas primeiramente por L.H. Ford, que são desigualdades sobre fluxos e densidades de energia negativa que impõem restrições capazes de tornar as violações acima não observáveis macroscopicamente. Nesta dissertação apresentaremos alguns exemplos de sistemas que possuem densidades ou fluxos de energia negativa, revisaremos os teoremas de Desigualdades Quânticas e discutiremos algumas de suas aplicações. Discutiremos também algumas limitações destes teoremas apresentando sistemas que não estão sujeitos a desigualdades quânticas, dos quais um exemplo é o próprio efeito Casimir. Iremos enfim propor um modelo que introduz flutuações quânticas nas condições de contorno (e.g., nas placas metálicas) do efeito Casimir, e iremos mostrar que a introdução destes efeitos de flutuação no cálculo da energia de Casimir tem por resultado impedir que violações de leis físicas macroscópicas manifeste-se nesse sistema.<br>Abstracts: It has been known for some time that Quantum Field Theory allows the violation of Classical Energy Conditions in the form of negative energy densities and fluxes. A remarkable exemple is the Casimir effect, where the vacuum state of the electromagnetic field between two perfectly conducting parallel plates presents negative energy density. However, if he laws of physics did not place constraints on such a violation of the Energy Conditions, it appears that it would be possible to use negative energies for producing, for example, macroscopic violation of the second law of thermodynamics, of the cosmic censorship conjecture, and also provide the creation of woemholes and time machines. A line of research wich was developed to approach this question is the so called Quantum Inequalities, first studied by L.H. Ford, which are constraints over negative energy densities and fluxes with capacity to render the above violations macroscopically unobservable. We present here some examples of systems with negative energy densities or fluxes, review the Quantum Inequalities theorems and discuss some of its applications. We also discuss some limitations of these theorems showing systems where there are no quantum inequalities, being the Casimir effect one example. At last we propose a model which introduces quantum fluctuations in the description of the boundaries conditions (e.g., the conducting plates) of Casimir effect and we'll show that the introduction of these fluctuations in the calculation of Casimir energy results in the impossibility of violation of macroscopic physical laws using Casimir configuration.
32
Ullio, Ícaro Joshua Morales. "Consequências da violação da simetria de Lorentz no Efeito Casimir." Universidade Federal da Paraíba, 2015. http://tede.biblioteca.ufpb.br:8080/handle/tede/8000.
Testo completoAbstract (sommario):
Submitted by Maike Costa (maiksebas@gmail.com) on 2016-03-16T11:18:29Z
No. of bitstreams: 1
arquivototal.pdf: 836345 bytes, checksum: 048933d0a290c347efd2fa4764bbcf63 (MD5)<br>Made available in DSpace on 2016-03-16T11:18:29Z (GMT). No. of bitstreams: 1
arquivototal.pdf: 836345 bytes, checksum: 048933d0a290c347efd2fa4764bbcf63 (MD5)
Previous issue date: 2015-02-20<br>In this Dissertation we’ll consider a scalar field theory where the breaking of Lorentz
symmetry is present. Basically we will adopt the Ho˘rava-Lifshtz theory. We’ll study the
modifications that an anisotropy in space-time produces in the Casimir effect. Let’s deal
with a massless real scalar field in two distinct situations: between parallel plates and
inside a two-dimensional rectangular box. In both cases we will adopt specific boundary
conditions on the field. As we shall see, the Casimir energy and force strongly depends
on the parameter associated with the breaking of Lorentz symmetry.<br>Nesse Dissertação consideraremos uma teoria de campo escalar onde a quebra da simetria
de Lorentz está presente. Basicamente adotaremos a teoria de Ho˘rava-Lifshtz.
Estudaremos as modificações que uma anisotropia no espaço-tempo produzem no efeito
Casimir. Vamos tratar um campo escalar real sem massa em duas situações distintas:
entre placas paralelas e no interior de uma caixa bidimensional retangular. Nos dois casos
adotaremos condições de contorno específicas sobre o campo. Como veremos, a energia e
a força de Casimir dependem fortemente do parametro associado a quebra da simetria de
Lorentz.
33
Laurent, Justine. "Mesures de la force de Casimir à basse température." Phd thesis, Grenoble, 2010. http://www.theses.fr/2010GRENY070.
Testo completoAbstract (sommario):
La force de Casimir, du nom du physicien qui prédit en 1948 l'existence de cette force attractive dans la configuration idéale de deux miroirs parfaits, plans et parallèles, est d'origine purement quantique. Elle résulte de l'existence des fluctuations quantiques de point zéro du champ électromagnétique et joue un rôle prépondérant dans le fonctionnement des nanosystèmes mécaniques en cours de développement et qui pourraient dans les années futures révolutionner l'industrie de la microélectronique. Pourtant, les effets correctifs liés à la conductivité des surfaces ou à l'empilement diélectrique des couches commencent seulement à être étudiés. L'objet du travail expérimental développé durant cette thèse a été la réalisation d'un appareil de mesure de forces faibles entre deux surfaces de tailles micrométriques en vue de l'étude de la force de Casimir. Nous avons adapté la technique mise au point au cours de la thèse de G. Jourdan à un environnement cryogénique afin d'atteindre les sensibilités en force requises pour l'étude de surfaces complexes. Ce manuscrit décrit ce nouvel appareil et ses performances. Nous avons ainsi étudié l'amortissement visqueux de notre sonde de force (un microlevier AFM avec une sphère collée à son extrémité) engendré par le confinement du fluide environnant. A 4 K, nous avons mis en évidence des effets opto-mécaniques induits par le bruit laser. Enfin, nos premiers tests entre deux surfaces d'or de faible rugosité nous ont amenés à lutter contre une force parasite. Nous avons déterminé l'origine de cette force et réussi à la contrer. La force de Casimir entre une sphère en or et un échantillon de silicium a alors pu être mesurée<br>The Casimir force, named after the Dutch physicist who predicted in 1948 the existence of this attractive force in an ideal conguration of two perfectly conducting and parallel plates, is due to quantum-mechanical effects. It results from electromagnetic fluctuations of vacuum and cannot be neglected anymore in the performance of the nano-mechanical systems (NEMS), which are currently developed and could also revolutionize the microelectronics industry. However, the study of the corrections brought by the surface conductivity or by the dielectric stacks has just started. This thesis work presents the achievement of a new instrument dedicated to the measurement of the Casimir force between two surfaces at the micron scale. We have adapted the technique performed during the G. Jourdan's PhD thesis to a cryogenic environment in order to reach the sensitivity needed to investigate complex surfaces. The viscous damping of the force probe (AFM cantilever) due to the environmental fluid confined between the sphere glued at the tip of the AFM cantilever and a sample has been analysed. Measurements at 4K have revealed an opto-mechanical effect induced by laser noise. Finally, our first tests between two low rough gold surfaces have showed the presence of a parasite force. We have found out the origin of this force and succeeded to remove it. The first measurement of the Casimir force between a gold sphere and a silicon sample has been performed
34
Baumgärtel, C., and Martin Tajmar. "The Planck Constant and the Origin of Mass due to a Higher Order Casimir Effect." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2018. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-237708.
Testo completoAbstract (sommario):
The Planck constant is one of the most important constants in nature, as it describes the world governed by quantum mechanics. However, it cannot be derived from other natural constants. We present a model from which it is possible to derive this constant without any free parameters. This is done utilizing the force between two oscillating electric dipoles described by an extension of Weber electrodynamics, based on a gravitational model by Assis. This leads not only to gravitational forces between the particles but also to a newly found Casimir-type attraction. We can use these forces to calculate the maximum point mass of this model which is equal to the Planck mass and derive the quantum of action. The result hints to a connection of quantum effects like the Casimir force and the Planck constant with gravitational ones and the origin of mass itself.
35
Espinosa, Jorge D. "De-wetting of cobalt thin films on sapphire." Morgantown, W. Va. : [West Virginia University Libraries], 2007. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=5314.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 2007.<br>Title from document title page. Document formatted into pages; contains ix, 106 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 102-105).
36
Reis, João Lucas Miqueleto. "Modelos análogos de gravitação semi-clássica usando circuitos supercondutores." reponame:Repositório Institucional da UFABC, 2017.
Cerca il testo completoAbstract (sommario):
Orientador: Prof. Dr. André Gustavo Scagliusi Landulfo<br>Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2017.<br>Essa dissertação de mestrado tem por objetivos estudar e discutir as bases matemáticas
e conceituais da teoria quântica de campos em espaços-tempos curvos (TQCEC)
e analisar como podemos simular efeitos de TQCEC, como o efeito Hawking e o efeito
Casimir dinâmico, usando circuitos supercondutores. Após o estudo do formalismo da
relatividade geral e da TQCEC, é feita uma revisão sobre os modelos análogos de gravitação
em fluidos. Em seguida analisamos a física dos chamados circuitos supercondutores
e estudamos como achar análogos de efeitos de TQCEC usando tais sistemas.<br>This dissertation aims to study and discuss the mathematical and conceptual basis of
quantum field theory in curved space-time (QFTCS) and analyse how we can simulate
QFTCS effects, such as the Hawking effect and the dynamical Casimir effect, using
superconducting circuits. After studying the general relativity formalism and QFTCS,
a review is done on analogue models of gravitation in fluids. Then we analyse the
physics of the so-called superconducting circuits and study how to find analogues of
QFTCS effects using such systems.
37
Hartmann, Michael [Verfasser], and Gert-Ludwig [Akademischer Betreuer] Ingold. "Casimir effect in the plane-sphere geometry: Beyond the proximity force approximation / Michael Hartmann ; Betreuer: Gert-Ludwig Ingold." Augsburg : Universität Augsburg, 2018. http://d-nb.info/1179089952/34.
Testo completo
38
Maia, Clóvis Achy Soares. "Fluxos e densidades de energia negativa em teoria quântica de campos /." São Paulo : [s.n.], 2005. http://hdl.handle.net/11449/91855.
Testo completoAbstract (sommario):
Orientador: George E. A. Matsas<br>Banca: Élcio Abdalla<br>Banca: Vitório Alberto De Lorenci<br>Resumo: Sabe-se já há algum tempo que a Teoria Quântica de Campos permite violações das Condições Clássicas de Energia na forma de densidades e fluxos de energia negativa. Um exemplo contundente é o efeito Casimir, onde o estado de vácuo do campo eletromagnético entre duas placas metálicas possui densidade de energia negativa. Porém, se as leis da física não colocassem restrições sobre tais violações das Condições de Energia, aparentemente seria possível usar energias negativas para, por exemplo, produzir violações macroscópicas da segunda lei da termodinâmica, da conjectura de cosmic censorship, além de se proporcionar a criação de wormholes e possíveis máquinas do tempo. Uma linha de pesquisa desenvolvida para abordar essa questão envolve as chamadas Desigualdades Quânticas, estudadas primeiramente por L.H. Ford, que são desigualdades sobre fluxos e densidades de energia negativa que impõem restrições capazes de tornar as violações acima não observáveis macroscopicamente. Nesta dissertação apresentaremos alguns exemplos de sistemas que possuem densidades ou fluxos de energia negativa, revisaremos os teoremas de Desigualdades Quânticas e discutiremos algumas de suas aplicações. Discutiremos também algumas limitações destes teoremas apresentando sistemas que não estão sujeitos a desigualdades quânticas, dos quais um exemplo é o próprio efeito Casimir. Iremos enfim propor um modelo que introduz flutuações quânticas nas condições de contorno (e.g., nas placas metálicas) do efeito Casimir, e iremos mostrar que a introdução destes efeitos de flutuação no cálculo da energia de Casimir tem por resultado impedir que violações de leis físicas macroscópicas manifeste-se nesse sistema.<br>Abstracts: It has been known for some time that Quantum Field Theory allows the violation of Classical Energy Conditions in the form of negative energy densities and fluxes. A remarkable exemple is the Casimir effect, where the vacuum state of the electromagnetic field between two perfectly conducting parallel plates presents negative energy density. However, if he laws of physics did not place constraints on such a violation of the Energy Conditions, it appears that it would be possible to use negative energies for producing, for example, macroscopic violation of the second law of thermodynamics, of the cosmic censorship conjecture, and also provide the creation of woemholes and time machines. A line of research wich was developed to approach this question is the so called Quantum Inequalities, first studied by L.H. Ford, which are constraints over negative energy densities and fluxes with capacity to render the above violations macroscopically unobservable. We present here some examples of systems with negative energy densities or fluxes, review the Quantum Inequalities theorems and discuss some of its applications. We also discuss some limitations of these theorems showing systems where there are no quantum inequalities, being the Casimir effect one example. At last we propose a model which introduces quantum fluctuations in the description of the boundaries conditions (e.g., the conducting plates) of Casimir effect and we'll show that the introduction of these fluctuations in the calculation of Casimir energy results in the impossibility of violation of macroscopic physical laws using Casimir configuration.<br>Mestre
39
Nefedchenko, Vasyl Fedorovych, Василий Федорович Нефедченко, Василь Федорович Нефедченко та О. Тверезовська. "Ефект Казимира". Thesis, Видавництво СумДУ, 2008. http://essuir.sumdu.edu.ua/handle/123456789/4171.
Testo completoAbstract (sommario):
В останні роки значно зріс інтерес до фізичних явищ, відомих під
загальною назвою “ефект Казимира”. Сутність цього ефекту полягає в
поляризації вакууму квантованих полів, яка виникає внаслідок зміни
спектра вакуумних коливань при обмеженні об’єму квантування або
при відмінності топології простору від евклідової.
При цитуванні документа, використовуйте посилання http://essuir.sumdu.edu.ua/handle/123456789/4171
40
Pavlov, Andrei [Verfasser], den Brink Jeroen [Akademischer Betreuer] van, den Brink Jeroen [Gutachter] van, Dmitri [Akademischer Betreuer] Efremov, Werner [Gutachter] Skrotzki, Eduard [Gutachter] Lavrov, and Steffen [Gutachter] Sykora. "Phonon-mediated Casimir effect / Andrei Pavlov ; Gutachter: Jeroen van den Brink, Werner Skrotzki, Eduard Lavrov, Steffen Sykora ; Jeroen van den Brink, Dmitri Efremov." Dresden : Technische Universität Dresden, 2019. http://d-nb.info/1227202105/34.
Testo completo
41
Büscher, Rauno. "Casimir forces and geometry." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=976592533.
Testo completo
42
Bellouvet, Maxime. "Condensation de Bose-Einstein et simulation d’une méthode de piégeage d’atomes froids dans des potentiels sublongueur d’onde en champ proche d’une surface nanostructurée." Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0265/document.
Testo completoAbstract (sommario):
Depuis plusieurs décennies un intérêt est né pour combiner deux systèmes quantiques pour former unsystème hybride quantique (SHQ) aux qualités qu’il serait impossible d’atteindre avec un seul des deuxsous-constituants. Parmi les systèmes quantiques, les atomes froids se distinguent par leur fort découplagede l’environnement, permettant un contrôle précis de leurs propriétés intrinsèques. En outre, les simulateursquantiques réalisés en piégeant des atomes froids dans des réseaux optiques présentent des propriétéscontrôlables (échelle d’énergie, géométrie,...) qui permettent d’étudier de nouveaux régimes intéressants enphysique de la matière condensée. Dans cette quête de phases quantiques exotiques (e.g., antiferromagnétisme),la réduction de l’entropie thermique est un défi crucial. Le prix à payer pour atteindre de si faiblestempérature et entropie est un long temps de thermalisation qui limite la réalisation expérimentale. La réductionde la période du réseau est une solution prometteuse pour augmenter la dynamique du système.Les SHQs avec des atomes froids offrent de riches perspectives mais requiert d’interfacer des systèmes quantiquesdans des états différents (solide/gaz) à des distances très proches, ce qui reste un défi expérimental.Le projet AUFRONS, dans lequel s’inscrit cette thèse, vise à refroidir un gaz d’atomes froids jusqu’aurégime de dégénérescence quantique puis de transporter et piéger ce nuage en champ proche d’une nanostructure.L’idée est d’obtenir un gaz d’atomes froids piégé dans un réseau bidimensionnel aux dimensionssublongueur d’onde, à quelques dizaines de nm de la structure. Un des objectifs est d’étudier les interactionsau sein du réseau mais également le couplage des atomes avec les modes de surface.Le travail réalisé durant cette thèse se décompose en une partie expérimentale et une partie théorique.Dans la première nous présentons le refroidissement d’atomes de 87Rb jusqu’au régime de dégénérescencequantique. La seconde partie est consacrée aux simulations théoriques d’une nouvelle méthode que nousavons implémentée pour piéger et manipuler des atomes froids à moins de 100 nm d’une nanostructure.Cette méthode, qui tire profit de la résonance plasmonique et des forces du vide (effet Casimir-Polder),permet de créer des potentiels sublongueur d’onde aux paramètres contrôlables. Nous détaillons ainsi lescalculs des forces optiques et des forces du vide que nous appliquons au cas d’un atome de 87Rb en champproche d’une nanostructure 1D<br>An interest for hybrid quantum systems (HSQs) has been growing up for the last decades. This object combines two quantum systems in order to take advantage of both systems’ qualities, not available withonly one. Among these quantum systems, ultracold atoms distinguish themselves by their strong decoupling from environment which enables an excellent control of their intrinsic properties. Optical lattice quantum simulators with tunable properties (energy scale, geometry,...) allows one to investigate new regimes incondensed matter physics. In this quest for exotic quantum phases (e.g., antiferromagnetism), the reduction of thermal entropy is a crucial challenge. The price to pay for such low temperature and entropy is a longthermalization time that will ultimately limit the experimental realization. Miniaturization of lattice spacingis a promising solution to speed up the dynamics. Engineering cold atom hybrids offers promising perspectives but requires us to interface quantum systems in different states of matter at very short distances, which still remains an experimental challenge.This thesis is part of the AUFRONS project, which aims at cooling down an atomic gas until the quantum degeneracy regime then transport and trap this cloud in the near field of a nanostructure. The idea is to trapcold atoms in a two-dimensional subwavelength lattice, at a few tenth of nm away from the surface. One goal is to study atom-atom interactions within the lattice but also atom-surface modes coupling.The work realized during this thesis splits into an experimental part and a theoretical part. In the firstone, we present the cooling of 87Rb atoms until the quantum degeneracy regime. The second part is dedicated to theoretical simulations of a new trapping method we have implemented to trap and manipulate cold atoms below 100 nm from structures. This method takes advantage of plasmonic resonance and vacuum forces (Casimir-Polder effect). It allows one to create subwavelength potentials with controllable parameters.We detail the calculations of optical and vacuum forces to apply them to an atom of 87Rb in the vicinity of a 1D nanostructure
43
Obadia, Nathaniel. "Le modèle de Davies-Fulling et ses généralisations : un modèle pour la radiation de Hawking." Tours, 2003. http://www.theses.fr/2003TOUR4002.
Testo completoAbstract (sommario):
Dans cette thèse nous reprenons, puis développons, le modèle de Davies-Fulling qui présente de nombreuses analogies avec la radiation engendrée par un Trou Noir. Ce modèle consiste en l'étude de la radiation émise par un miroir se déplaçant dans l'espace-temps de Minkowski. Lorsque la trajectoire est non-inertielle, le miroir engendre un flux d'énergie dont les propriétés sont des fonctionnelles de sa trajectoire. Dans le but de retrouver les problèmes présents dans l'étude de la radiation de Hawking, nous nous sommes interessés principalement au cas des miroirs uniformément accélérés, qui possèdent un horizon causal. Afin de résoudre les problèmes pour la radiation engendrée par de tels miroirs, nous avons introduit un nouveau modèle, qui dérive cette fois d'une action. Un choix précis et motivé du Lagrangien nous a permis d'y parvenir. De plus, grâce à deux méthodes complémentaires, nous avons explicité les corrélations quantiques présentes dans le flux émis.
44
De, Aquino Carvalho Joao Carlos. "Interaction Casimir-Polder entre atome de césium et surface de saphir thermiquement émissive." Thesis, Sorbonne Paris Cité, 2018. http://www.theses.fr/2018USPCD054.
Testo completoAbstract (sommario):
Nous décrivons dans cette thèse des mesures spectroscopiques de réflexion sélective qui mettent en évidence les effets thermiques de l'interaction Casimir-Polder entre atome et surface. En régime de champ proche, cette interaction est gouvernée par un potentiel qui décroit avec le cube de la distance entre l'atome et la surface (régime van der Waals -vdW-de type dipôle-dipôle). Nous nous intéressons notamment aux niveaux excités du césium Cs (7P₁/₂) et Cs (7P₃/₂), qui possèdent un couplage dipolaire avec Cs (6D) à, respectivement, 12,15 µm et ~15 µm, interagissant avec une surface de saphir thermiquement émissive dont les modes émetteurs sont situés autour de 12,2 µm. Ainsi, ces niveaux respectifs niveaux sont sensibles à une interaction vdW résonante, ou non-résonante, que nous comparons expérimentalement Le résultat le plus important de cette thèse est l'observation expérimentale de la différence de comportement du potentiel vdW en fonction de la température de fenêtre (150-800 °C), pour les niveaux Cs(7P₁/₂) et Cs (7P₃/₂). Pour le niveau Cs (7P₁/₂) le potentiel vdW augment en fonction de la température, tandis que pour le niveau une légère décroissance est observée. Des expériences de spectroscopie de réflexion sélective sondant le niveau Cs (6P₁/₂), interagissant avec une surface de saphir chaude, ont aussi été réalisées, qui confirment pour ce niveau l'absence d'effet de température. Les prédictions théoriques sont raffinées par l'évaluation de la constante diélectrique du saphir en fonction de la température, à partir de données nouvelles d'émissivité fournies par le groupe CEMHTI à Orléans. Enfin, utilisant la fluorescence rétrodiffuse comme diagnostic pour la cellule chaude de Cs lorsque l'excitation était faite sur les niveaux Cs (6P ₁/₂) et Cs (7P ₁/₂), nous avons interprété de façon plus consistante que les propositions précédentes de la littérature, des structures sub-Doppler observées dans l'excitation de la fluorescence au voisinage de la fenêtre<br>In this thesis we describe measurements of selective reflection spectroscopy that highlight the thermal effects of the Casimir-Polder interaction between atom and surface. In the near field regime, this interaction is governed by a potential decreasing with the cube of the distance between the atom and the surface (van der Waals -vdW- regime of dipoledipole type) We are particularly interested in the excited levels of cesium, we are particularly interested in the excited levels of cesium Cs (7P₁/₂) and Cs (7P₃/₂), which have a dipole coupling to respectively Cs (6D) at 12,15 µm and ~15 µm interacting with a thermally emissive sapphire surface. Sapphire emitting modes are around 12,2 µm, and, thus, these Cs levels are sensitive to a resonant, or non-resonant, vdW interaction. We compare experimentally these levels. The most important result of this thesis is the experimental observation of the difference in behavior of the vdW potential as a function of the window temperature (150 - 800 °C), for the Cs (7P₁/₂) and Cs (7P₃/₂) levels. For the Cs (7P₁/₂) level the vdW potential increases as a function of temperature, while for the Cs (7P₃/₂) level a slight decrease is observed. Selective reflection spectroscopy experiments, probing the Cs (6P₁/₂) level interacting with a hot sapphire surface, were also carried out, which confirm for this level the absence of a temperature effect. The theoretical predictions are refined by the evaluation of the dielectric constant of sapphire as a function of temperature, from new emissivity data provided by the CEMHTI's group, in Orléans. Finally, we use backscattered fluorescence as a diagnosis for the Cs hot cell when exciting Cs (6P ₁/₂) and Cs (7P ₁/₂) levels. We have interpreted, in a manner more consistent than previous literature, sub-Doppler structures observed in the excitation of the fluorescence near the window
45
Bugler-Lamb, Samuel Lloyd. "The quantum vacuum near time-dependent dielectrics." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/29879.
Testo completoAbstract (sommario):
The vacuum, as described by Quantum Field Theory, is not as empty as classical physics once led us to believe. In fact, it is characterised by an infinite energy stored in the ground state of its constituent fields. This infinite energy has real, tangible effects on the macroscopic clusters of matter that make up our universe. Moreover, the configuration of these clusters of matter within the vacuum in turn influences the form of the vacuum itself and so forth. In this work, we shall consider the changes to the quantum vacuum brought about by the presence of time-dependent dielectrics. Such changes are thought to be responsible for phenomena such as the simple and dynamical Casimir effects and Quantum Friction. After introducing the physical and mathematical descriptions of the electromagnetic quantum vacuum, we will begin by discussing some of the basic quasi-static effects that stem directly from the existence of an electromagnetic ground state energy, known as the \textit{zero-point energy}. These effects include the famous Hawking radiation and Unruh effect amongst others. We will then use a scenario similar to that which exhibits Cherenkov radiation in order to de-mystify the 'negative frequency' modes of light that often occur due to a Doppler shift in the presence of media moving at a constant velocity by showing that they are an artefact of the approximation of the degrees of freedom of matter to a macroscopic permittivity function. Here, absorption and dissipation of electromagnetic energy will be ignored for simplicity. The dynamics of an oscillator placed within this moving medium will then be considered and we will show that when the motion exceeds the speed of light in the dielectric, the oscillator will begin to absorb energy from the medium. It will be shown that this is due to the reversal of the 'radiation damping' present for lower velocity of stationary cases. We will then consider how the infinite vacuum energy changes in the vicinity, but outside, of this medium moving with a constant velocity and show that the presence of matter removes certain symmetries present in empty space leading to transfers of energy between moving bodies mediated by the electromagnetic field. Following on from this, we will then extend our considerations by including the dissipation and dispersion of electromagnetic energy within magneto-dielectrics by using a canonically quantised model referred to as 'Macroscopic QED'. We will analyse the change to the vacuum state of the electromagnetic field brought about by the presence of media with an arbitrary time dependence. It will be shown that this leads to the creation of particles tantamount to exciting the degrees of freedom of both the medium and the electromagnetic field. We will also consider the effect these time-dependencies have on the two point functions of the field amplitudes using the example of the electric field. Finally, we will begin the application of the macroscopic QED model to the path integral methods of quantum field theory with the purpose of making use of the full range of perturbative techniques that this entails, leaving the remainder of this adaptation for future work.
46
Devailly, Clémence. "Fluctuations thermiques - un outil pour étudier les fluides simples et binaires à l'échelle du micron." Thesis, Lyon, École normale supérieure, 2014. http://www.theses.fr/2014ENSL0976.
Testo completoAbstract (sommario):
Les transitions de phase près d'un point critique - dites du second ordre - sont un sujet toujours d'actualité en raison des nombreux phénomènes critiques intéressants tels que la force de Casimir critique, les problèmes de confinements ou les phénomènes hors d'équilibre suivant une trempe au point critique. Cette thèse vise à étudier expérimentalement certains phénomènes engendrés près d'un point critique. La thèse est divisée en deux axes : le premier consiste à développer plusieurs systèmes expérimentaux qui permettront de mesurer essentiellement la viscosité, par l'intermédiaire des fluctuations thermiques à l'échelle micrométrique. Le deuxième axe consiste à trouver et caractériser des mélanges binaires présentant une transition de phase du second ordre dans lesquelles on souhaite faire des mesures. Les enjeux de ces systèmes expérimentaux sont d'avoir une régulation en température précise, une sonde de mesure sensible aux fluctuations thermiques et/ou à des forces de l'ordre du pN, et un échantillon fiable et reproductible présentant un point critique accessible expérimentalement. Nous avons ainsi monté à partir d'un microscope à force atomique (AFM) déjà présent au laboratoire, un système de mesure de viscosité à sonde AFM fibrée. Malgré sa faible efficacité en terme de sonde de mesure métrologique, nous avons pu décrire et développer un modèle de couplage de modes de vibration permettant de comprendre la mécanique de microleviers AFM fibrés. J'ai également développé au laboratoire la mesure de microscopie dynamique différentielle qui permet de faire des mesures à sondes multiples contrairement au premier montage. J'ai discuté de la précision de la mesure dans le cadre de notre objectif d'étude des fluctuations critiques. En ce qui concerne l'échantillon de mesure, nous avons étudié plusieurs mélanges binaires que nous avons caractérisés par des méthodes classiques de turbidité et diffusion statique de la lumière. Cette caractérisation nous a permis de connaître les mélanges binaires pour les utiliser dans un troisième système de mesure : billes micrométriques piégées dans des pinces optiques déjà monté au laboratoire. Nous y avons rajouté un système de régulation thermique fait maison pour être exploité avec les contraintes de la pince optique. Ces tests ont fait apparaître un phénomène inattendu d'oscillations de transition de phase induites par laser. Nous avons développé un modèle pour les décrire. Enfin, des expériences préliminaires - toujours avec les pinces optiques dans les mélanges binaires - nous ont permis d'observer qualitativement des effets de l'approche au point critique par des mesures de viscosité et d'interaction type force de Casimir critique<br>Phase transitions near a critical point, or second order phase transitions, are still a recent object of studies because of the large amount of interesting critical phenomena as the critical Casimir force, confinements problems or out of equilibrium phenomena following a quench at the critical point. This thesis experimentally studies phenomena near a critical point. This manuscript is divided in two parts : the first one consists in building several experimental set-up which measure viscosity through thermal fluctuation at micrometric scale. The second part consists in finding and characterize binary mixtures which show a second order phase transition. Preliminary results have been done in these samples. One of the principal points of these experimental set-up are a well regulated temperature, a probe sensitive to thermal fluctuation and/or pN forces and a reproducible binary mixture which presents a critical point easy to reach experimentally. We mounted from an Atomic Force Microscope (AFM) already built in the laboratory, a hanging-fiber probe to measure viscosity of liquids. Despite its weak efficiency as a metrologic probe, we described and developed a mode coupling model which let us understand mechanics of hanging-fiber probes. I also developed in the lab the dynamic differential microscopy technique (DDM) which do measurements with several probes. I discussed about the measure precision with in mind the aim of studying critical fluctuations. For the choice of the sample, we studied several binary mixtures. We characterized them by classical methods as turbidity measurements and static light scattering. These characterizations let us learn about binary mixtures in order to use them in a third experimental set-up : beads trapped in an optical tweezers already built in the lab. We added to it a home-made thermal regulation which can be used with the constraints of optical tweezers. These tests showed an unexpected phenomenon of oscillating phase transition induce by laser. We developed a model to describe it. At last, preliminary experiments with optical tweezers in binary mixtures showed qualitative effects of an approach near a critical point on the viscosity and on interactions between beads as critical Casimir force
47
Hertlein, Johann Christopher. "Messung kritischer Casimir-Kräfte mit TIRM." [S.l. : s.n.], 2008. http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-37124.
Testo completo
48
Maury, Axel. "Effet Casimir-Polder sur des atomes piégés." Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066327/document.
Testo completoAbstract (sommario):
Ce travail de thèse présente la modélisation théorique de l'expérience FORCA-G. L'objectif de cette expérience est la mesure des interactions à courte portée entre des atomes piégés dans un réseau optique et une surface massive à une grande précision. Nous nous sommes intéressés plus particulièrement à l'effet Casimir-Polder induit par la surface sur les atomes. Le but était de fournir la prédiction la plus précise possible des états atomiques. Ceci a consisté à considérer les effets de la température sur l'interaction Casimir-Polder et modéliser la surface de la manière la plus réaliste possible. Afin de résoudre le problème de divergence qu'impliquait un traitement perturbatif de l'interaction atome-surface, nous avons développé une méthode numérique pour un traitement non-perturbatif de l'interaction Casimir-Polder et modélisé l'interaction atome-surface à très courte distance par un potentiel de Lennard-Jones. Chaque effet et incertitude sur les états atomiques ont été évalués afin de déterminer s'ils seraient observables ou un facteur limitant en regard de la précision visée par l'expérience. Enfin nous nous sommes intéressés au cas d'un déséquilibre thermique entre la température du miroir et la température de l'environnement qui pourrait être induit par les lasers en présence ou un laser de chauffage. Nous avons calculé la correction du potentiel Casimir-Polder due au déséquilibre et évalué l'effet sur les niveaux d'énergie atomiques pour déterminer si cet effet pouvait être mesuré<br>This thesis presents the theoretical modeling of the experiment FORCA-G. The purpose of this experiment is to measure short-range interactions between trapped atoms in an optical lattice and a massive surface with a high precision. We are focused on Casimir-Polder effect induced by the surface on the atoms. The aim was to give the most possible precise prediction of atomic states. This work took the temperature effects on Casimir-Polder interaction into account, modelled the surface of the experiment. In order to solve the divergence problem due to the perturbative treatment of the atom-surface interaction, we developed a digital method for a non-perturbative treatment of the Casimir-Polder interaction and modelled the short-range atom-surface interaction by a Lennard-Jones potential. Each effect and uncertainties on the atomic states were evaluated so that we know if they could be observable or a limiting factor compared to the experiment precision. Finally we were focused on an out of thermal equilibrium situation between the miroir and environment temperature which may be induced by the lasers. We computed the correction to the Casimir-Polder potential due to this disequilibrium and evaluated the effect on the atomic states
49
Busch, Xavier. "Effets dispersifs et dissipatifs en théorie quantique des champs en espace-temps courbe pour modéliser des systèmes de matière condensée." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112205/document.
Testo completoAbstract (sommario):
Les deux principales prédictions de la théorie quantique des champs en espace-temps courbe, à savoir la radiation de Hawking et la production de paires de particules ayant lieu dans un espace-temps non stationnaire, n'ont jamais été testé expérimentalement et impliquent toutes deux des processus à ultra haute énergie. En conséquence, de telles prédictions doivent être considérées prudemment. En utilisant l'analogie avec des systèmes de matière condensée mise en avant par Unruh, leur analogue pourrait être testé en laboratoire. Par ailleurs, dispersion et dissipation sont toujours présentes dans de tels systèmes, ce qui régularise la théorie à courte distances. Lors d'expériences destinées à tester les prédictions citées ci-dessus, le bruit thermique modifiera le résultat. En effet, il existe une compétition entre l'émission stimulée dudit bruit thermique et l'émission spontanée issue du vide quantique. Afin de mesurer la radiation de Hawking analogue et de l'analogue des productions de paires (souvent appelé effet Casimir dynamique), il est alors nécessaire de calculer les conséquence de la dispersion et de la dissipation, ainsi que d'identifier des observables permettant de certifier que l'amission spontanée a eu lieu. Dans cette thèse, nous analyserons d'abord les effets de la dispersion et de la dissipation à la fois sur la radiation de Hawking et sur la production de paires de particules. Afin d'obtenir des résultats explicites, nous travaillerons avec l'espace-temps de de Sitter. Les symétries de la théorie nous permettront d'obtenir des résultats exacts. Ceux-ci seront alors appliqués aux trous noirs grâce aux ressemblances entre la région proche du trou noir et l'espace de de Sitter. Afin d’introduire de la dissipation, nous considérerons un modèle exactement soluble permettant de modéliser n'importe quel taux de dissipation. Dans un tel modèle, le champ est couplé de manière linéaire à un environnement contenant un ensemble dense de degrés de liberté. Dans un tel contexte, nous étudierons l'intrication des particules produites. Ensuite, nous considérerons des systèmes de matière condensée spécifiques, à savoir les condensats de Bose et les polaritons. Nous analyserons les effets de la dissipation sur l'intrication de l’effet Casimir dynamique. Enfin, nous étudieront de manière générique l'intrication de la radiation de Hawking en présence de dispersion pour des systèmes analogues<br>The two main predictions of quantum field theory in curved space-time, namely Hawking radiation and cosmological pair production, have not been directly tested and involve ultra high energy configurations. As a consequence, they should be considered with caution. Using the analogy with condensed matter systems put forward by Unruh, their analogue versions could be tested in the lab. Moreover, the high energy behavior of these systems is known and involved dispersion and dissipation, which regulate the theory at short distances. When considering experiments which aim to test the above predictions, the thermal noise will contaminate the outcome. Indeed, there will be a competition between the stimulated emission from thermal noise and the spontaneous emission out of vacuum. In order to measure the quantum analogue Hawking radiation, or the analogue pair production also called dynamical Casimir effect, one should thus compute the consequences of ultraviolet dispersion and dissipation, and identify observables able to establish that the spontaneous emission took place. In this thesis, we first analyze the effects of dispersion and dissipation on both Hawking radiation and pair particle production. To get explicit results, we work in the context of de Sitter space. Using the extended symmetries of the theory in such a background, exact results are obtained. These are then transposed to the context of black holes using the correspondence between de Sitter space and the black hole near horizon region. To introduce dissipation, we consider an exactly solvable model producing any decay rate. In such a model, the field is linearly coupled to an environment containing a dense set of degrees of freedom. We also study the quantum entanglement of the particles so produced. In a second part, we consider explicit condensed matter systems, namely Bose Einstein condensates and exciton-polariton systems. We analyze the effects of dissipation on entanglement produced by the dynamical Casimir effect. As a final step, we study the entanglement of Hawking radiation in the presence of dispersion for a generic analogue system
50
Intravaia, Francesco. "Effet Casimir et interaction entre plasmons de surface." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2005. http://tel.archives-ouvertes.fr/tel-00009755.
Testo completoAbstract (sommario):
Dans cette thèse on discute l'influence des plasmons de surfaces sur l'effet Casimir entre deux miroirs métalliques plans et parallèles placés à une distance arbitraire. En utilisant le model plasma pour décrire la réponse optique du métal, on exprime l'énergie de Casimir comme une somme des contributions associées aux modes évanescents relatifs aux plasmons de surface et aux modes propagatifs de la cavité. Contrairement à une ce qu'on pouvait attendre, la contribution des modes plasmoniques est essentielle à toute distance afin d'assurer le correct résultat pour l'énergie de Casimir. Un des deux modes plasmoniques génère une contribution répulsive qui compense la contribution attractive provenant des modes propagatifs de la cavité, alors que les deux contributions, prises séparément, sont beaucoup plus importantes que la valeur réelle pour l'énergie de Casimir. Cela suggère qu'il est possible d'ajuster le signe de la force de Casimir en manipulant les plasmons de surface.