Finite-well potential in the 3D nonlinear Schroedinger equation: Application to Bose-Einstein condensation

Using variational and numerical solutions we show that stationary negative-energy localized (normalizable) bound states can appear in the three-dimensional nonlinear Schr\"odinger equation with a finite square-well potential for a range of nonlinearity parameters. Below a critical attractive nonlinearity, the system becomes unstable and experiences collapse. Above a limiting repulsive nonlinearity, the system becomes highly repulsive and cannot be bound. The system also allows nonnormalizable states of infinite norm at positive energies in the continuum. The normalizable negative-energy bound states could be created in BECs and studied in the laboratory with present knowhow.Comment: 8 pages, 12 figure

Loss of superfluidity in a Bose-Einstein condensate via forced resonant oscillations

We predict the loss of superfluidity in a Bose-Einstein condensate in an axially symmetric harmonic trap alone during resonant collective oscillations via a classical dynamical transition. The forced resonant oscillation can be initiated by (a) a periodic modulation of the atomic scattering length with a frequency that equals twice the radial trapping frequency or multiples thereof, or by (b) a periodic modulation of the radial trapping potential with a frequency that equals the radial trapping frequency or multiples thereof. Suggestion for future experiment is made.Comment: 12 Latex Pages, 12 eps figures, Accepted in Physics Letters

Josephson oscillation of a superfluid Fermi gas

Using the complete numerical solution of a time-dependent three-dimensional mean-field model we study the Josephson oscillation of a superfluid Fermi gas (SFG) at zero temperature formed in a combined axially-symmetric harmonic plus one-dimensional periodic optical-lattice (OL) potentials after displacing the harmonic trap along the axial OL axis. We study the dependence of Josephson frequency on the strength of the OL potential. The Josephson frequency decreases with increasing strength as found in the experiment of Cataliotti et al. [Science 293 (2001) 843] for a Bose-Einstein condensate and of the experiment of Pezze et al. [Phys. Rev. Lett. 93 (2004) 120401] for an ideal Fermi gas. We demonstrate a breakdown of Josephson oscillation in the SFG for a large displacement of the harmonic trap. These features of Josephson oscillation of a SFG can be tested experimentally.Comment: 7 pages, 10 figure

Josephson oscillation and induced collapse in an attractive Bose-Einstein condensate

Using the axially-symmetric time-dependent Gross-Pitaevskii equation we study the Josephson oscillation of an attractive Bose-Einstein condensate (BEC) in a one-dimensional periodic optical-lattice potential. We find that the Josephson frequency is virtually independent of the number of atoms in the BEC and of the inter-atomic interaction (attractive or repulsive). We study the dependence of Josephson frequency on the laser wave length and the strength of the optical-lattice potential. For a fixed laser wave length (795 nm), the Josephson frequency decreases with increasing strength as found in the experiment of Cataliotti {\it et al.} [Science {\bf 293}, 843 (2001)]. For a fixed strength, the Josephson frequency remains essentially unchanged for a reasonable variation of laser wave length around 800 nm. However, for a fixed strength, the Josephson oscillation is disrupted with the increase of laser wave length beyond 2000 nm leading to a collapse of a sufficiently attractive BEC. These features of Josephson oscillation can be tested experimentally with present set ups.Comment: 7 pages, 12 ps and eps figures, Physical Review

Entanglement and Teleportation in Bipartite System

We present a mathematical formulation of old teleportation protocol (original teleportation protocol introduced by Bennett et.al.) for mixed states and study in detail the role of mixedness of the two qubit quantum channel in a teleportation protocol. We show that maximally entangled mixed state described by the density matrix of rank-4 will be useful as a two qubit teleportation channel to teleport a single qubit mixed state when the teleportation channel parameter p1 greater than 0.5. Also we discuss the case when p1 less than equal to 0.5.Comment: 16 pages and 5 figures. Accepted in IJQ

Market-based Approaches to Environmental Management: A Review of Lessons from Payment for Environmental Services in Asia

Market-based approaches to environmental management, such as payment for environmental services (PES), have attracted unprecedented attention during the past decade. PES policies, in particular, have emerged to realign private and social benefits such as internalizing ecological externalities and diversifying sources of conservation funding as well as making conservation an attractive land-use paradigm. In this paper, we review several case studies from Asia on payment for environmental services to understand how landowners decide to participate in PES schemes. The analysis demonstrates the significance of four major elements facilitating the adoption and implementation of PES schemes: property rights and tenure security, transaction costs, household and community characteristics, communications, and the availability of PES-related information. PES schemes should target win-win options through intervention in these areas, aimed at maintaining the provision of ecological services and improving the conditions for local inhabitants

Bring your own devices classroom : issues of digital divides in teaching and learning contexts : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Information Technology at Massey University, Albany campus, New Zealand

Since the late 1990s, digital divide has gathered much attention from the research community and government organizations. The education sector has been an important area of inquiry for many researchers, as they strive to inform government initiatives on strategies to address digital divide issues prevalent here. This study reports on how existing and new digital divides have evolved with increased penetration of digital learning technologies into teaching and learning practices and the wide usage of enabling technologies by students across formal and informal learning spaces (i.e. both in- and out-of-school), within the context of a BYOD (bring your own device) classroom initiative. A five-year longitudinal investigation of a BYOD classroom initiative by a New Zealand school helped to gain insights into different nature of digital divides in the learning process. First, the BYOD classroom initiative did not end up accentuating existing gaps in access to digital devices and information, despite initial results indicating towards a potentially digitally divided classroom. Second, the study strongly indicated the presence of gaps in terms of information literacy and critical thinking ability, which was eventually bridged in the later stage, as students slowly adjusted to the classroom curricular structures in the BYOD classroom. Third, learner self-efficacy has been identified as the most influential determinant of learning outcomes among students. In earlier phases of investigation of BYOD classrooms initiative, learner self-efficacy was found to be influenced by digital capability, in combination with information literacy, critical thinking ability, and positive motivation. However subsequently, self-efficacy influences affordances in various aspects of social cognitive abilities related to individual’s learning activities affecting how learners engage and apply technology to shape their learning outcomes. The study findings will inform policy makers and education government agencies, in their ongoing quest for bringing about inclusive digital transformation and overall improvement in learning outcomes

Interactions and Correlations of Particulate Inclusions in a Columnar Phase

We calculate the elastic field mediated interaction between macroscopic particles in a columnar hexagonal phase. The interaction is found to be long-ranged and non-central, with both attractive and repulsive parts. We show how the interaction modifies the particle correlations and the column fluctuations. We also calculate the interaction of particles with the topological defects of the columnar phase. The particle-defect interaction reduces the mobility of the defects.Comment: RevTeX4 8 pages, 4 eps figures, submitted to Euro. Phys. J.

Estimation of Entanglement Negativity of a Two-Qubit Quantum System With Two Measurements

Numerous work had been done to quantify the entanglement of a two-qubit quantum state, but it can be seen that previous works were based on joint measurements on two copies or more than two copies of a quantum state under consideration. In this work, we show that a single copy and two measurements are enough to estimate the entanglement quantifier like entanglement negativity and concurrence. To achieve our aim, we establish a relationship between the entanglement negativity and the minimum eigenvalue of structural physical approximation of partial transpose of an arbitrary two-qubit state. The derived relation make possible to estimate entanglement negativity experimentally by Hong-Ou-Mandel interferometry with only two detectors. Also, we derive the upper bound of the concurrence of an arbitrary two-qubit state and have shown that the upper bound can be realized in experiment. We will further show that the concurrence of (i) an arbitrary pure two-qubit states and (ii) a particular class of mixed states, namely, rank-2 quasi-distillable mixed states, can be exactly estimated with two measurements.Comment: 6 pages, 2 figures, Published versio