Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 41 for “"quantum fluctuations"”.
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Aspects of Quantum Fluctuations under Time-dependent External Influences
The vacuum of quantum field theory is not empty space but filled with quantum vacuum fluctuations, which give rise to many intriguing effects. The first part of this Thesis addresses cosmic inflation, where the quantum fluctuations of the inflaton field freeze and get amplified in the expanding …
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An Exploration of Quantum Critical Phenomena in One-Dimensional Lattice Systems: Geometric Frustration & Quantum Fluctuations
… of critical phenomena within one-dimensional quantum lattice spin systems. People are exposed to classical critical phenomena everyday in the form of phase transitions, such as from water to ice. Surrounding quantum phase transitions, there is a number of exciting phenomena still to be …
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Some Numerical and Phenomenological Studies in Loop Quantum Cosmology
… feature of the singularity resolution in loop quantum cosmology (LQC) is the occurrence of the quantum bounce when the spacetime curvature becomes comparable to the Planck scale. The presence of quantum bounce greatly modifies the dynamics of the early universe and can have important …
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Fluctuation-induced phenomena in non-equilibrium systems
… this thesis, we investigate the implications of fluctuations in systems away, possibly even far, from equilibrium due to their motion either in or out of thermal equilibrium. This subject encompasses several topics in physics including the dynamical Casimir effect in the presence of moving …
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Frustrated Magnetism in Strongly Correlated Electron Systems
… induced as a result of magnetic frustration and quantum fluctuations. We show that emergent spin textures can arise close to a magnetic field-induced quantum critical point, when the single magnon excitations have several degenerate non-coplanar minima. In this case, quantum fluctuations can lift …
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The fate of inflation fluctuations in multi-field scenarios during inflation
… in cosmology. Furthermore, we study the quantum fluctuations of a generic scalar field during inflation while putting the emphasis on the different behaviour of the fluctuations in or out of the horizon. Finally, we consider an inflationary potential composed of two coupled scalar fields: …
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Searching for novel objects in the electroweak theory
… configurations. We consider heavy fermion quantum fluctuations about static Higgs-Gauge configurations, and argue for the existence of stable fermionic solitons. These could resolve the fermion decoupling puzzle in chiral gauge theories. We describe our search for a fermionic soliton within …
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Casimir-Polder interaction in second quantization
… atom and a nearby surface, arising from the (quantum and thermal) fluctuations of the electromagnetic field, is a cornerstone of cavity quantum electrodynamics (cQED), and theoretically well established. Recently, Bose-Einstein condensates (BECs) of ultracold atoms have been used to test the …
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The Runny Gauge Plasma: shear viscosity to entropy for quarks and gluons
… properties of the QGP, within the theory of quantum chromodynamics (QCD). Meaningful approximations of most observables require quantum fluctuations to be taken into account. These arise in perturbation theory as loop corrections to tree level amplitudes, and describe both the …
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Novel applications of Maxwell's equations to quantum and thermal phenomena
… our contributions to the efforts to describe quantum fluctuations, known as Casimir forces, in terms of classical electromagnetism. We prove that chirality in metamaterials can have no appreciable effect on the Casimir force, and design an alternative metamaterial in which the structure can …
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Toward quantum opto-mechanics in a gram-scale suspended mirror interferometer
… will closely approach the fundamental quantum limits of measurement, serving as a prominent example of quantum mechanics at the macroscale. Simultaneously, numerous experiments involving micro-mechanical oscillators are beginning to explore the quantum regime, with the help of optical …
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Fluctuations in dc SQUIDs: Quantum Noise Effects, Low Frequency Noise, and Single Electron Trapping
… is expected to be limited by intrinsic quantum fluctuations, making these devices prime candidates for ideal quantum-limited detectors. The observed signal properties are excellent and a minimum for energy resolution of 1.6$\hbar$ was measured at 1.5K, the lowest value reported to date. …
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An action principle for dissipative fluid dynamics
… encodes the effects of thermal and quantum fluctuations. In our formulation, the dynamical degrees of freedom are Stuckelberg-type fields associated to the conserved quantities, which are subject to natural symmetry considerations, and the time evolution of the path integral is along …
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Fluctuation-mediated interactions of atoms and surfaces on a mesoscopic scale
Thermal and quantum fluctuations of the electromagnetic near field of atoms and macroscopic bodies play a key role in quantum electrodynamics (QED), as in the Lamb shift. They lead, e.g., to atomic level shifts, dispersion interactions (Van der Waals-Casimir-Polder interactions), and state …
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Quantum Effects of the Massless Spin One-Half Field in Static Spherically Symmetric Black Hole and Wormhole Spacetimes
… temperature vacuum state. We treat the field quantum mechanically on a classical background spacetime governed by general relativity. The full stress-energy tensor is found to be finite and regular for all spacetimes. We make comparisons between the numerical calculation and the analytic …
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Terahertz spectroscopy of quantum spin liquids
… Herbertsmithite is proposed to exhibit Quantum Spin Liquid behavior, in which electron spins have strong antiferromagnetic interactions, but quantum fluctuations inhibit magnetic order even at 0 K, instead giving way to a Resonating Valence Bond state. Quantum Spin Liquids host exotic …
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Dynamical correlations of S=1/2 quantum spin chains
… some of the striking effects of interactions and quantum fluctuations in one-dimensional systems. The XXZ model has been used to study the unusual properties of anisotropic spin chains in an external magnetic field. The zero temperature phase diagram for this model exhibits a critical or …
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Pairing symmetry, competing orders, and quantum criticality in iron based superconductors via London penetration depth measurements
… reaches a maximum. This may arise from quantum fluctuations associated with a quantum critical point buried beneath the superconducting dome.
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Little Big Bangs in Helium-Three
… dynamics of the pair subspace, as initiated by quantum fluctuations, tends irreversibly to a self-driven steady state with a gap 1 = C(e2/N(0) − 1)−1/2. In weak coupling this is half the equilibrium
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Quantum Optics and Mechanics in Gravitational-Wave Detectors
… the Sun, yet they remain at the whim of minute quantum fluctuations. Pushing our reach further into the cosmos demands a mastery over these quantum effects. In recent years, we have entered the era of quantum-enhanced gravitational-wave detection, wherein the injection of squeezed states has …
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