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Full-Text Articles in Engineering Science and Materials
Quantum Simulations Of Low Dimensional Systems And Analytic Continuation Of Imaginary Time Correlation Functions, Nathan Scott Nichols
Quantum Simulations Of Low Dimensional Systems And Analytic Continuation Of Imaginary Time Correlation Functions, Nathan Scott Nichols
Graduate College Dissertations and Theses
For over thirty years, a long standing problem in quantum many-body physics has been to reliably extract dynamical information from imaginary time quantum Monte Carlo data. I report on a new method developed using modern evolutionary computation routines to approach this notoriously ill-posed problem. Motivation towards a solution will be presented as a brief summary of work on quantum simulations of low dimensional systems including helium on strained graphene and helium confined within rare gas plated mesoporous silica. The Differential Evolution for Analytic Continuation (DEAC) algorithm reconstructs the dynamic structure factor from imaginary time density-density correlations at zero and finite …
Path Integral Quantum Monte Carlo Study Of Coupling And Proximity Effects In Superfluid Helium-4, Max Graves
Path Integral Quantum Monte Carlo Study Of Coupling And Proximity Effects In Superfluid Helium-4, Max Graves
Graduate College Dissertations and Theses
When bulk helium-4 is cooled below T = 2.18 K, it undergoes a phase transition to a superfluid, characterized by a complex wave function with a macroscopic phase and exhibits inviscid, quantized flow. The macroscopic phase coherence can be probed in a container filled with helium-4, by reducing one or more of its dimensions until they are smaller than the coherence length, the spatial distance over which order propagates. As this dimensional reduction occurs, enhanced thermal and quantum fluctuations push the transition to the superfluid state to lower temperatures. However, this trend can be countered via the proximity effect, where …