Effects of disorder on quantum fluctuations and superfluid density of a Bose-Einstein condensate in a two-dimensional optical lattice

We investigate a Bose-Einstein condensate trapped in a 2D optical lattice in the presence of weak disorder within the framework of the Bogoliubov theory. In particular, we analyze the combined effects of disorder and an optical lattice on quantum fluctuations and superfluid density of the BEC system. Accordingly, the analytical expressions of the ground state energy and quantum depletion of the system are obtained. Our results show that the lattice still induces a characteristic 3D to 1D crossover in the behavior of quantum fluctuations, despite the presence of weak disorder. Furthermore, we use the linear response theory to calculate the normal fluid density of the condensate induced by disorder. Our results in the 3D regime show that the combined presence of disorder and lattice induce a normal fluid density that asymptotically approaches 4/3 of the corresponding condensate depletion. Conditions for possible experimental realization of our scenario are also proposed.Comment: 8 pages, 0 figure. To appear in Physical Review

Optically trapped quasi-two-dimensional Bose gases in random environment: quantum fluctuations and superfluid density

We investigate a dilute Bose gas confined in a tight one-dimensional (1D) optical lattice plus a superimposed random potential at zero temperature. Accordingly, the ground state energy, quantum depletion and superfluid density are calculated. The presence of the lattice introduces a crossover to the quasi-2D regime, where we analyze asymptotically the 2D behavior of the system, particularly the effects of disorder. We thereby offer an analytical expression for the ground state energy of a purely 2D Bose gas in a random potential. The obtained disorder-induced normal fluid density $n_n$ and quantum depletion $n_d$ both exhibit a characteristic $1/\ln\left(1/n_{2D}a_{2D}^{2}\right)$ dependence. Their ratio $n_n/n_d$ increases to $2$ compared to the familiar $4/3$ in lattice-free 3D geometry, signifying a more pronounced contrast between superfluidity and Bose-Einstein condensation in low dimensions. Conditions for possible experimental realization of our scenario are also proposed.Comment: 8 pages, 2 figure

A cross-country study of mis-implementation in public health practice

Abstract Background Mis-implementation (i.e., the premature termination or inappropriate continuation of public health programs) contributes to the misallocation of limited public health resources and the sub-optimal response to the growing global burden of chronic disease. This study seeks to describe the occurrence of mis-implementation in four countries of differing sizes, wealth, and experience with evidence-based chronic disease prevention (EBCDP). Methods A cross-sectional study of 400 local public health practitioners in Australia, Brazil, China, and the United States was conducted from November 2015 to April 2016. Online survey questions focused on how often mis-termination and mis-continuation occur and the most common reasons programs end and continue. Results We found significant differences in knowledge of EBCDP across countries with upwards of 75% of participants from Australia (n = 91/121) and the United States (n = 83/101) reporting being moderately to extremely knowledgeable compared with roughly 60% (n = 47/76) from Brazil and 20% (n = 21/102) from China (p < 0.05). Far greater proportions of participants from China thought effective programs were never mis-terminated (12.2% (n = 12/102) vs. 1% (n = 2/121) in Australia, 2.6% (n = 2/76) in Brazil, and 1.0% (n = 1/101) in the United States; p < 0.05) or were unable to estimate how frequently this happened (45.9% (n = 47/102) vs. 7.1% (n = 7/101) in the United States, 10.5% (n = 8/76) in Brazil, and 1.7% (n = 2/121) in Australia; p < 0.05). The plurality of participants from Australia (58.0%, n = 70/121) and the United States (36.8%, n = 37/101) reported that programs often mis-continued whereas most participants from Brazil (60.5%, n = 46/76) and one third (n = 37/102) of participants from China believed this happened only sometimes (p < 0.05). The availability of funding and support from political authorities, agency leadership, and the general public were common reasons programs continued and ended across all countries. A program’s effectiveness or evidence-base—or lack thereof—were rarely reasons for program continuation and termination. Conclusions Decisions about continuing or ending a program were often seen as a function of program popularity and funding availability as opposed to effectiveness. Policies and practices pertaining to programmatic decision-making should be improved in light of these findings. Future studies are needed to understand and minimize the individual, organizational, and political-level drivers of mis-implementation