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Showing 1 to 20 of 27 for “"Path integrals"”.
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Path integrals on ultrametric spaces
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 1994.
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Path integrals and the quantum Routhian
… coordinates. Starting from the phase space path integral, we derive an expression for the quantum mechanical propagator of a system written in terms of its Routhian. We then go on to show how this formalism can provide calculational simplifications in simple situations such as a free …
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Path integrals on manifolds with boundary and their asymptotic expansions
… on a Riemannian manifold can be represented by a path integral. However, the problem with such path integrals is that they are notoriously ill-defined. One way to make them rigorous (which is often applied in physics) is finite-dimensional approximation, or time-slicing approximation: Given a fine …
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Conductance of single-electron devices from imaginary-time path integrals
… Our theoretical description is based on a <br>path-integral expression for the current autocorrelation function <br>which can be related to the conductance using linear response <br>theory. To circumvent the dynamical sign problem in the numerical <br>determination of real-time correlation …
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Escape processes far from thermal equilibrium : path integrals and force spectroscopy
… the second part of this thesis, the technique of path integration is employed to develop an approximation to the instantaneous escape rate that applies to arbitrarily modulated potentials and temperatures. As such systems are far from thermal equilibrium, the physics is not restricted by the …
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Quantum dynamics in the condensed phase: path integrals, master equations and purity
… propagator (QuAPI) and the quantum-classical path integral (QCPI). In particular, we present the incorporation of Langevin friction by eliminating classical trajectories, and a time-dependent driving field to study light-matter interactions, to the framework of QCPI. We further introduce the …
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Tunneling Systems in Condensed Phases: Quantum Dynamical Monte Carlo and Analytical Theories
… Carlo method for the evaluation of real time path integrals at finite temperatures is proposed. The technique is applied to two level tunneling systems coupled to many body environments, models for electron transfer and for the quantum coherence phenomenon in Josephson junctions. A dynamical …
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Brownian motion and multidimensional decision making
… and page numbering. Part I, "Potential theory, path integrals and the Laplacian of the indicator", finds the transition density of absorbed or reflected Brownian motion in a d-dimensional domain as a Feynman-Kac functional involving the Laplacian of the indicator, thereby relating the hitherto …
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The effects of instantons in a finite temperature quantum field theory
In this thesis we describe the Euclidean path integral approach and instanton methods for investigating a SU(2) Yang-Mills theory at finite temperature. We first begin with a review of tunneling in a one-dimensional periodic potential. Here we introduce the methods of Euclidean path integrals and …
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CP-Violation and Baryogenesis on Electroweak Scales
… actions based on the worldline representation of path integrals. The main part of the present work deals with transport theory of quantum systems. Based on the derivation of quantum transport equations for one flavour we generalize to mixing systems with several flavours. One prominent and novel …
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On the exact renormalization of states in quantum field theories
… quantum features of field theories. By using path integral methods, we can port our understanding of the renormalization of Euclidean field theories to states of the QFT Hilbert space. Such constructions require the use of manifolds with boundary in the path integral, presenting technical and …
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On extended supersymmetry in two and four dimensions.
… { a special deformation used in localization of path integrals of supersymmetric theories. Instead of performing the localization we treat the Omega background physically and study BPS solitons for such theories, albeit the latter already possess less supersymmetry. Theories with N = 2 SUSY in …
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Dynamical signatures of instantons: insights from path-integral studies
… quantified using imaginary-time Feynman path integrals. While traditionally used as a method to account for static quantum effects of atomic nuclei, the path-integral framework has also been augmented to simulate short-time quantum dynamics using essentially classical molecular-dynamics …
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Describing Charge Transfer in Extended Donor-Acceptor Systems with Density Functional Theory
… We discuss a procedure on the basis of density path integrals that transforms the BJ potential into a functional derivative of a corresponding energy expression.
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THE THEORY OF COMBINATORY DIFFERENTIATION AND LOCALITY IN QUANTUM CHEMISTRY
… connection between the combinatory logic and path integrals through a little bit of differential geometry captured in just two equations. This work started as an attempt to automate the differentiation process in quantum mechanics using fundamental concepts in programming language theories. It …
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Matsubara Dynamics and its Practical Implementation
… Matsubara dynamics is based on Feynman's path integral formulation of quantum mechanics and is expected to describe the physics of any system that satisfies quantum Boltzmann statistics and exhibits rapid quantum decoherence, e.g. liquid water at room temperature. Having derived the …
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Quasicentroid Molecular Dynamics
… subject to thermally averaged Feynman path fluctuations (“the mean field”). This theory approximates the dynamics of systems at thermal equilibrium that follow quantum Boltzmann statistics and undergo rapid quantum decoherence. As it relies on purely classical mechanics, the theory …
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Magnetization dynamics of single molecule magnets
Made available in DSpace on 2014-09-16T17:25:53Z (GMT). No. of bitstreams: 2 Yun_Liu.pdf: 2936489 bytes, checksum: 870b4bdf8c282c749cf14f4925088600 (MD5) license.txt: 4056 bytes, checksum: c0d6bd6324ecaf18c5d2647589f9beff (MD5)
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Phase space and path integral approaches to quantum dynamics
… this problem, we propose a numerically exact path integral based method which can be systematically converged to any desired level of accuracy at increasing computational cost. Both these methods can be used with quantum classical simulation frameworks. Second, we present developments of rate …
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