Relaxation and thermalization of nonequilibrium quantum systems in the semiclassical limit
Embargo Date
Indefinite
OA Version
Citation
Abstract
We discuss the development and application of semiclassical techniques to study dynamics and relaxation in quantum mechanical systems out of equilibrium, relevant to ultracold atomic gases. Due to the unprecedented amount of control in these systems, experimentalists have a lot of freedom in designing Hamiltonians, including the spatial dimension. Another advantage present in these systems is the fact that time scales are slow enough, in contradistinction with usual condensed matter systems, so that it is possible to follow nonequilibrium dynamics and relaxation after quantum quenches. The advent of these experiments has motivated us to further understand these systems. With this goal in mind, we apply a semiclassical phase space technique called Truncated Wigner Approximation (TWA) to study dynamics in the weakly interacting, semiclassical limit. In our study, we will further confine ourselves to one dimensional systems where thermalization is poorly understood due to the fact that generic one dimensional Hamiltonians lie close to integrable models. Due to the peculiarity of systems in low dimensions, such as the prohibition of true long range order, these systems relax in an interesting way, and we generically find the emergence of long-lived metastable states. In particular, we find it is possible to design Hamiltonians that share features with the Fermi-Pasta-Ulam model, and these systems relax to a metastable state where different momentum mode energies live at different temperatures.
Description
Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.