Maximum thickness of a two-dimensional trapped Bose system

The trapped Bose system can be regarded as two-dimensional if the thermal fluctuation energy is less than the lowest energy in the perpendicular direction. Under this assumption, we derive an expression for the maximum thickness of an effective two-dimensional trapped Bose system.Comment: 1 pages, 0 figure

An optical lattice on an atom chip

Optical dipole traps and atom chips are two very powerful tools for the quantum manipulation of neutral atoms. We demonstrate that both methods can be combined by creating an optical lattice potential on an atom chip. A red-detuned laser beam is retro-reflected using the atom chip surface as a high-quality mirror, generating a vertical array of purely optical oblate traps. We load thermal atoms from the chip into the lattice and observe cooling into the two-dimensional regime where the thermal energy is smaller than a quantum of transverse excitation. Using a chip-generated Bose-Einstein condensate, we demonstrate coherent Bloch oscillations in the lattice.Comment: 3 pages, 2 figure

Collapsing dynamics of attractive Bose-Einstein condensates

The self-similar collapse of 3D and quasi-2D atom condensates with negative scattering length is examined. 3D condensates are shown to blow up following the scenario of {\it weak collapse}: The inner core of the condensate diverges with an almost zero particle number, while its tail distribution spreads out to large distances with a constant density profile. For this case, the 3-body recombination arrests the collapse, but it weakly dissipates the atoms. The confining trap then reforms the condensate at later times. In contrast, 2D condensates undergo a {\it strong collapse}: The atoms stay mainly located at center and recombination sequentially absorbs a significant amount of particles.Comment: 4 pages, submitted for publicatio

Killed a Bird Today: The Emergence and Functionality of the Santeria Trickster, Eleggua

Recognizable by their cunning exploits and gray morality, tricksters can be found in mythology, folklore, and religions throughout the world. Two tricksters were familiar to the Yoruba people in West Africa, Ajapa and Eshu, and their stories and abilities provide insight to the functions fulfilled by trickster characters. Upon the introduction of Regla de Ocha (or Santeria) to Cuba following the transatlantic slave trade, a new figure emerges, known for his tricks and adaptability. Due to the West African influence in Santeria religious practices, the original roles and traits of Eshu and Ajapa are analyzed for comparison, but Eleggua, the Santeria trickster, has become his own entity. Through ethnographic observations, personal conversations, and a collection of various sources and manuals, this project explores Eleggua and the trickster presence in Cuba. Although his role as a trickster has changed throughout the past few centuries, Eleggua and the trickster identity persists in modern Cuba, visible in religious practices and secular exchanges

Frequencies and Damping rates of a 2D Deformed Trapped Bose gas above the Critical Temperature

We derive the equation of motion for the velocity fluctuations of a 2D deformed trapped Bose gas above the critical temperature in the hydrodynamical regime. From this equation, we calculate the eigenfrequencies for a few low-lying excitation modes. Using the method of averages, we derive a dispersion relation in a deformed trap that interpolates between the collisionless and hydrodynamic regimes. We make use of this dispersion relation to calculate the frequencies and the damping rates for monopole and quadrupole mode in both the regimes. We also discuss the time evolution of the wave packet width of a Bose gas in a time dependent as well as time independent trap.Comment: 13 pages, latex fil

Dilute Bose gas in two dimensions: Density expansions and the Gross-Pitaevskii equation

A dilute two-dimensional (2D) Bose gas at zero temperature is studied by the method developed earlier by the authors. Low density expansions are derived for the chemical potential, ground state energy, kinetic and interaction energies. The expansion parameter is found to be a dimensionless in-medium scattering amplitude u obeying the equation 1/u+\ln u=-\ln(na^2\pi)-2\gamma, where na^2 and \gamma are the gas parameter and the Euler constant, respectively. It is shown that the ground state energy is mostly kinetic in the low density limit; this result does not depend on a specific form of the pairwise interaction potential, contrary to 3D case. A new form of 2D Gross-Pitaevskii equation is proposed within our scheme.Comment: 4 pages, REVTeX, no figure

Reforming Peru’s Political Institutions : The Role of Good Governance Aid as a Driver of Change

Decades-long debates over the quality, quantity and purpose of development aid have led to a renewed emphasis on whether, and under what circumstances, aid is effective in achieving development outcomes. There is significant policy consensus that aid is most effective in environments with “good” governance, which the United Nations defines as processes of decision making and implementation that are effective and efficient, equitable and inclusive, and accountable and transparent. Aid donors fund numerous projects aimed at strengthening good governance in recipient countries, often through reforms of political institutions. Yet many aid donors fail to theorize about the process or mechanism through which good governance aid drives institutional change, and in doing so often ignore the impact that other drivers of change may have on the implicitly assumed direct causal relationship between aid and improved governance in political institutions. This thesis explores the role of aid in shifting institutions toward the ideal of good governance through an analysis that embeds this aid within a larger context that takes into account the role of other drivers of change. It compares good governance-related changes within Peru’s judicial institutions and Comptroller (Auditor) General over a 30-year period, from 1980-2010, examining the main actors and factors that drove or influenced changes in institutional accountability, transparency, effectiveness and efficiency, asking how they drove these changes and overcame resistance to reforms. Building upon this within-case analysis, this thesis then compares across cases to develop conclusions about the necessary and sufficient conditions that resulted in positive good governance-related changes. It concludes with a discussion of the opportunities for, and limitations of, good governance aid as a driver of change in political institutions

Creating a low-dimensional quantum gas using dark states in an inelastic evanescent-wave mirror

We discuss an experimental scheme to create a low-dimensional gas of ultracold atoms, based on inelastic bouncing on an evanescent-wave mirror. Close to the turning point of the mirror, the atoms are transferred into an optical dipole trap. This scheme can compress the phase-space density and can ultimately yield an optically-driven atom laser. An important issue is the suppression of photon scattering due to ``cross-talk'' between the mirror potential and the trapping potential. We propose that for alkali atoms the photon scattering rate can be suppressed by several orders of magnitude if the atoms are decoupled from the evanescent-wave light. We discuss how such dark states can be achieved by making use of circularly-polarized evanescent waves.Comment: 8 pages, 4 figure

Two-dimensional atom trapping in field-induced adiabatic potentials

We show how to create a novel two-dimensional trap for ultracold atoms from a conventional magnetic trap. We achieve this by utilizing rf-induced adiabatic potentials to enhance the trapping potential in one direction. We demonstrate the loading process and discuss the experimental conditions under which it might be possible to prepare a 2D Bose condensate. A scheme for the preparation of coherent matterwave bubbles is also discussed

Multi Mode Interferometer for Guided Matter Waves

We describe the fundamental features of an interferometer for guided matter waves based on Y-beam splitters and show that, in a quasi two-dimensional regime, such a device exhibits high contrast fringes even in a multi mode regime and fed from a thermal source.Comment: Final version (accepted to PRL