Thermodynamics of the superfluid dilute Bose gas with disorder

We generalize the Beliaev-Popov diagrammatic technique for the problem of interacting dilute Bose gas with weak disorder. Averaging over disorder is implemented by the replica method. Low energy asymptotic form of the Green function confirms that the low energy excitations of the superfluid dirty Boson system are sound waves with velocity renormalized by the disorder and additional dissipation due to the impurity scattering. We find the thermodynamic potential and the superfluid density at any temperature below the superfluid transition temperature and derive the phase diagram in temperature vs. disorder plane.Comment: 4 page

The Energy of a Trapped Interacting Bose Gas

A Bose gas in an external potential is studied by means of the semi-classical approximation. Analytical results are derived for the energy of an interacting Bose gas in a generic power-law trapping potential. An expression for the chemical potential below the critical temperature is also obtained. The theoretical results are in qualitative agreement with a recent energy measurement.Comment: 6 pages, REVTex, one figure

Ferromagnetism in a lattice of Bose condensates

We show that an ensemble of spinor Bose-Einstein condensates confined in a one dimensional optical lattice can undergo a ferromagnetic phase transition and spontaneous magnetization arises due to the magnetic dipole-dipole interaction. This phenomenon is analogous to ferromagnetism in solid state physics, but occurs with bosons instead of fermions.Comment: 4 pages, 2 figure

Fate of a Bose-Einstein condensate with attractive interaction

We calculate the decay amplitude of a harmonically trapped Bose-Einstein condensate with attractive interaction via the Feynman path integral. We find that when the number of particles is less than a critical number, the condensate decays relatively slowly through quantum tunneling. When the number exceeds the critical one, a "black hole" opens up at the center of the trap, in which density fluctuations become large due to a negative pressure, and collisional loss will drain the particles from the trap. As the black hole is fed by tunneling particles, we have a novel system in which quantum tunneling serves as a hydrodynamic source.Comment: 3 pages, REVTeX; email to [email protected] (Kerson Huang

Critical Behaviour of Superfluid 4^4He in Aerogel

We report on Monte Carlo studies of the critical behaviour of superfluid $^4$He in the presence of quenched disorder with long-range fractal correlations. According to the heuristic argument by Harris, uncorrelated disorder is irrelevant when the specific heat critical exponent $\alpha$ is negative, which is the case for the pure $^4$He. However, experiments on helium in aerogel have shown that the superfluid density critical exponent $\zeta$ changes. We hypothesize that this is a cross-over effect due to the fractal nature of aerogel. Modelling the aerogel as an incipient percolating cluster in 3D and weakening the bonds at the fractal sites, we perform XY-model simulations, which demonstrate an increase in $\zeta$ from $0.67 \pm 0.005$ for the pure case to an apparent value of $0.722\pm 0.005$ in the presence of the fractal disorder, provided that the helium correlation length does not exceed the fractal correlation length.Comment: 4 pages, RevTex, 3 postscript figures, LaTeX file and figures have been uuencoded

The Good, the Bad and the Ugly: A Study of the Organization through the Lens of Popular Films of the Western World

This chapter examined portrayals of the morality of organizations using the lens of Western films. The work explored six decades of film, analyzing the organizational contexts and their agents, in order to understand filmmakers’ and audiences’ perceptions of organizational settings. In order to examine the organization as an entity within film, this chapter provided a content analysis of plot summaries from a purposefully selected body of top grossing box office films spanning 60 years. The plot summaries constituted a strong basis for identifying the characteristics of the organization as they are largely descriptive in nature and as such do not offer any evaluation or analysis of the film. Any assumptions about the character of organizations (or their members/employees) are unconscious, and as such they constitute a verbal description of what competent observers would say has occurred within the film. The plots were coded to reveal perceptions of positive, neutral, or negative organizational contexts and actions. This approach exposed the filmmakers symbolic placing of the organization in order to provide backdrops for the narrative. The plot analysis revealed that throughout the decades there has been a sophisticated portrayal in film of the role of the organization and the agents therein. A generally negative view of organizational contexts was demonstrated, with only religion and education shown as positive within the films selected. It was recognized that there would be value in extending this research to analyze a larger body of works. The selection criteria resulted in a wide but not comprehensive corpus of film genres. The body of works was sufficient to reveal the complexity of attitudes to organizational values and delivery which has evolved through time. Different selection criteria and more substantial narrative text could serve to confirm these results. Further implications for future research were discussed. While in the real-life sphere, there has been an emphasis on organizational standards and “corporate governance” delivering ethical exemplars, the film contexts highlight the complexities of delivering trusted organizations. The reality that there remains the potential for organizational corruption is well understood by the general public and clearly depicted within the film world. The conceptual contribution is original as limited work has been conducted on the organizational context in films. This work revealed the possibility of using this approach to further develop a greater understanding of perceptions of organizations

Citizen science for observing and understanding the Earth

Citizen Science, or the participation of non-professional scientists in a scientific project, has a long history—in many ways, the modern scientific revolution is thanks to the effort of citizen scientists. Like science itself, citizen science is influenced by technological and societal advances, such as the rapid increase in levels of education during the latter part of the twentieth century, or the very recent growth of the bidirectional social web (Web 2.0), cloud services and smartphones. These transitions have ushered in, over the past decade, a rapid growth in the involvement of many millions of people in data collection and analysis of information as part of scientific projects. This chapter provides an overview of the field of citizen science and its contribution to the observation of the Earth, often not through remote sensing but a much closer relationship with the local environment. The chapter suggests that, together with remote Earth Observations, citizen science can play a critical role in understanding and addressing local and global challenges

Orthogonal metals: The simplest non-Fermi liquids

We present a fractionalized metallic phase which is indistinguishable from the Fermi liquid in conductivity and thermodynamics, but is sharply distinct in one-electron properties, such as the electron spectral function. We dub this phase the “orthogonal metal.” The orthogonal metal and the transition to it from the Fermi liquid are naturally described using a slave-particle representation wherein the electron is expressed as a product of a fermion and a slave Ising spin. We emphasize that when the slave spins are disordered, the result is not a Mott insulator (as erroneously assumed in the prior literature), but rather the orthogonal metal. We construct prototypical ground-state wave functions for the orthogonal metal by modifying the Jastrow factor of Slater-Jastrow wave functions that describe ordinary Fermi liquids. We further demonstrate that the transition from the Fermi liquid to the orthogonal metal can, in some circumstances, provide a simple example of a continuous destruction of a Fermi surface with a critical Fermi surface appearing right at the critical point. We present exactly soluble models that realize an orthogonal metal phase, and the phase transition to the Fermi liquid. These models thus provide valuable solvable examples for phase transitions associated with the death of a Fermi surface.National Science Foundation (U.S.) (Grant DMR-1005434