The Boson-Hubbard Model on a Kagome Lattice with Sextic Ring-Exchange Terms

High order ring-exchange interactions are crucial for the study of quantum fluctuations on highly frustrated systems. We present the first exact quantum Monte Carlo study of a model of hard-core bosons with sixth order ring-exchange interactions on a two-dimensional kagome lattice. By using the Stochastic Green Function algorithm, we show that the system becomes unstable in the limit of large ring-exchange interactions. It undergoes a phase separation at all fillings, except at 1/3 and 2/3 fillings for which the superfluid density vanishes and an unusual mixed valence bond and charge density ordered solid is formed.Comment: 4 pages, 7 figure

Let them Moodle: Utilizing an open source learning management system to extend the English classroom

The purpose of the project was to install a Moodle installation on a server and deploy it to select teachers while developing a series of training modules to help assist teachers to utilize Moodle as an online supplement to their classroom teaching. The goal was to give the teachers involved an additional outlet for learning beyond the classroom setting. Specifically, this project centered on creating video tutorials and a demo class aimed to help teachers utilize this powerful medium. Moodle activities are items such as blogs, forums, wikis, and quizzes among many other learner-centric technologies. The participants to pilot this project were found by asking for volunteers at an English department meeting at Hesperia High School in Southern California. Three teachers volunteered. With the researcher included, this would put the pilot participants at four teachers with five classes each

Complex phases in the doped two-species bosonic Hubbard Model

We study a two-dimensional bosonic Hubbard model with two hard-core species away from half filling using Quantum Monte Carlo simulations. The model includes a repulsive interspecies interaction and different nearest-neighbor hopping terms for the two species. By varying the filling we find a total of five distinct phases, including a normal liquid phase at higher temperature, and four different phases at lower temperature. We find an anti-ferromagnetically ordered Mott insulator and a region of coexistent anti-ferromagnetic and superfluid phases near half filling. Further away from half filling the phase diagram displays a superfluid phase and a novel phase inside the superfluid region at even lower temperatures. In this novel phase separated region, the heavy species has a Mott behavior with integer filling, while the lighter species shows phase separated Mott and superfluid behaviors.Comment: 5 pages, 4 figure

Phase diagram of the Bose-Hubbard model on a ring-shaped lattice with tunable weak links

Motivated by recent experiments on toroidal Bose-Einstein condensates in all-optical traps with tunable weak links, we study the one-dimensional Bose-Hubbard model on a ring-shaped lattice with a small region of weak hopping integrals using quantum Monte Carlo simulations. Besides the usual Mott insulating and superfluid phases, we find a phase which is compressible but non superfluid with a local Mott region. This `local Mott' phase extends in a large region of the phase diagram. These results suggest that the insulating and conducting phases can be tuned by a local parameter which may provide a new insight to the design of atomtronic devices.Comment: 5 pages, 5 figure

Political Decentraliza tion in Socialist France: Alternative Theories--AIternative Struggles

A unitary, strongly centralized state has characterized French political thought and practice for centuries. The Socialist Party broke from this tradition during its recent tenure in national office when it passed a comprehensive program of political decentralization. We consider these recent changes in the structure of the French state from pluralist, elitist, and ruling class perspectives, and conclude that each of these traditional conceptualizations limits our understanding of state power in various ways. We explore the utility of a refined ruling class perspective known as social capital, and suggest it offers insights into political decentralization and state structure not provided by alternative perspectives. We conclude by suggesting that social capital holds promise for application to problems of analytical and practical significance

Does French Matter? France and Francophonie in the Age of Globalization

THE ORGANISATION INTERNATIONALE DE LA FRANCOPHONIE (OIF) increasingly acts as a powerful French-speaking voice in defense of both French culture and language and in advancing French-speaking nations\u27 multiple global, political and economic interests. While the OIF includes developed as well as developing1 nations, its policies and financial resources come from its wealthier and more economically powerful members, fueling charges that it exists to represent those members\u27 interests. The OIF is unique among international organizations in propounding economic policies based on assumptions different from those espoused by the World Trade Organization (WTO). These differences become most apparent in OIF\u27s strong stance supporting cultural exceptions in international trade. This article examines the claims pursued by the OIF, the issue of whose interests are being served, and prospects for its future

Point singularities and suprathreshold stochastic resonance in optimal coding

Motivated by recent studies of population coding in theoretical neuroscience, we examine the optimality of a recently described form of stochastic resonance known as suprathreshold stochastic resonance, which occurs in populations of noisy threshold devices such as models of sensory neurons. Using the mutual information measure, it is shown numerically that for a random input signal, the optimal threshold distribution contains singularities. For large enough noise, this distribution consists of a single point and hence the optimal encoding is realized by the suprathreshold stochastic resonance effect. Furthermore, it is shown that a bifurcational pattern appears in the optimal threshold settings as the noise intensity increases. Fisher information is used to examine the behavior of the optimal threshold distribution as the population size approaches infinity.Comment: 11 pages, 3 figures, RevTe

Ferromagnetic phase in the polarized two-species bosonic Hubbard model

We recently studied a doped two-dimensional bosonic Hubbard model with two hard-core species, with different masses, using quantum Monte Carlo simulations [Hettiarachchilage, Phys. Rev. B 88, 161101(R) (2013)PRBMDO1098-012110.1103/PhysRevB.88.161101]. Upon doping away from half filling, we find several distinct phases, including a phase-separated ferromagnet with Mott behavior for the heavy species and both Mott-insulating and superfluid behaviors for the light species. Introducing polarization, i.e., an imbalance in the population between species, we find a fully phase-separated ferromagnet. This phase exists for a broad range of temperatures and polarizations. By using finite-size scaling of the susceptibility, we find a critical exponent which is consistent with the two-dimensional Ising universality class. Significantly, since the global entropy of this phase is higher than that of the ferromagnetic phase with single species, its experimental observation in cold atoms may be feasible