Back-reaction of perturbation wave packets on gray solitons

Within the Bogoliubov-de Gennes linearization theory of quantum or classical perturbations around a background solution to the one-dimensional nonlinear Schr\"odinger equation, we study the back-reaction of wave packet perturbations on a gray soliton background. From our recently published exact solutions, we determine that a wave packet effectively jumps ahead as it passes through a soliton, emerging with a wavelength-dependent forward translation in comparison to its motion in absence of the soliton. From this and from the full theory's exact momentum conservation, we deduce that post-Bogoliubov back-reaction must include a commensurate forward advance by the soliton itself. We quantify this effect with a simple theory, and confirm that it agrees with full numerical solution of the classical nonlinear Schr\"odinger equation. We briefly discuss the implications of this effect for quantum behavior of solitons in quasi-condensed dilute gases at finite temperature.Comment: 12 pages, 2 figure

Asset Mapping and Focus Group Usage: An Exploration of the Russian-Ukrainian Population’s Need For and Use of Health-Related Community Resources

Community resources are an important aspect of preventive medicine and can also provide support to individuals with existing medical conditions. However, resources may not address all population groups within the community equally, and immigrants, who frequently face cultural and language barriers, are often unable to access the full range of healthcare resources available in the community. The purpose of this study was to gain insight on healthcare needs, attitudes, and access of a Ukrainian immigrant population in a large town in northern Indiana. Focus groups were conducted as a first step to creating connections upon which a community-based participatory research project could be built. Findings revealed cultural barriers (lack of understanding of health insurance options or value, belief that similar services were less expensive in the Ukraine) and language issues (lack of translation services or resources written in languages other than English or Spanish) were key barriers to accessing healthcare resources in the community. Concerns about dental care and its expense were also voiced. Future efforts might build on these findings by exploring policies and practices that affect various immigrant groups’ access to community healthcare resources. Recommendations for such efforts are also discussed

A Narrative in One Scene

Filmmakers are visual storytellers, thus it is important to understand basic film theory as well as the elements of a narrative, such as voice, look, and feel. It is just as important for filmmakers to understand how film theory and the elements of a narrative work together to effectively convey stories to the people viewing the film. In this thesis, I researched basic film theory and analyzed three personally influential movies and directors including Charlie Chaplin’s Modern Times (1936), Juan Antonio Bayona’s The Impossible (2012), and Akira Kurosawa’s The Seven Samurai (1954). I chose one technique from each of the the films, synthesized them into an original scene, and described the process of creating the scene

Winding up by a quench: vortices in the wake of rapid Bose-Einstein condensation

A second order phase transition induced by a rapid quench can lock out topological defects with densities far exceeding their equilibrium expectation values. We use quantum kinetic theory to show that this mechanism, originally postulated in the cosmological context, and analysed so far only on the mean field classical level, should allow spontaneous generation of vortex lines in trapped Bose-Einstein condensates of simple topology, or of winding number in toroidal condensates.Comment: 4 pages, 2 figures; misprint correcte

Inhibition of spontaneous emission in Fermi gases

Fermi inhibition is a quantum statistical analogue for the inhibition of spontaneous emission by an excited atom in a cavity. This is achieved when the relevant motional states are already occupied by a cloud of cold atoms in the internal ground state. We exhibit non-trivial effects at finite temperature and in anisotropic traps, and briefly consider a possible experimental realization.Comment: 4 pages with 3 figure

Deconstructing Decoherence

The study of environmentally induced superselection and of the process of decoherence was originally motivated by the search for the emergence of classical behavior out of the quantum substrate, in the macroscopic limit. This limit, and other simplifying assumptions, have allowed the derivation of several simple results characterizing the onset of environmentally induced superselection; but these results are increasingly often regarded as a complete phenomenological characterization of decoherence in any regime. This is not necessarily the case: The examples presented in this paper counteract this impression by violating several of the simple ``rules of thumb''. This is relevant because decoherence is now beginning to be tested experimentally, and one may anticipate that, in at least some of the proposed applications (e.g., quantum computers), only the basic principle of ``monitoring by the environment'' will survive. The phenomenology of decoherence may turn out to be significantly different.Comment: 13 two-column pages, 3 embedded figure

Second-quantized Landau-Zener theory for dynamical instabilities

State engineering in nonlinear quantum dynamics sometimes may demand driving the system through a sequence of dynamically unstable intermediate states. This very general scenario is especially relevant to dilute Bose-Einstein condensates, for which ambitious control schemes have been based on the powerful Gross-Pitaevskii mean field theory. Since this theory breaks down on logarithmically short time scales in the presence of dynamical instabilities, an interval of instabilities introduces quantum corrections, which may possibly derail a control scheme. To provide a widely applicable theory for such quantum corrections, this paper solves a general problem of time-dependent quantum mechanical dynamical instability, by modelling it as a second-quantized analogue of a Landau-Zener avoided crossing: a `twisted crossing'.Comment: 4 pages, 3 figure