Electrodynamics of Bose-Einstein condensates in angular motion

A theory determining the electric and magnetic properties of vortex states in Bose-Einstein condensates (BECs) is presented. The principal ingredient is the Lagrangian of the system which we derive correct to the first order in the atomic centre of mass velocity. For the first time using centre of mass coordinates, a gauge transformation is performed and relevant relativistic corrections are included. The Lagrangian is symmetric in the electric and magnetic aspects of the problem and includes two key interaction terms, namely the Aharanov-Casher and the Roentgen interaction terms. The constitutive relations, which link the electromagnetic fields to the matter fields via their electric polarisation and magnetisation, follow from the Lagrangian as well as the corresponding Hamiltonian. These relations, together with a generalised Gross-Pitaevskii equation, determine the magnetic (electric) monopole charge distributions accompanying an order n vortex state when the constituent atoms are characterised by an electric dipole (magnetic dipole). Field distributions associated with electric dipole active (magnetic dipole active) BECs in a vortex state are evaluated for an infinite- and a finite-length cylindrical BEC. The predictd monopole charge distributions, both electric and magnetic, automatically satisfy the requirement of global charge neutrality and the derivations highlight the exact symmetry between the electric and magnetic properties. Order of magnitude estimates of the effects are given for an atomic gas BEC, superfluid helium and a spin-polarised hydrogen BEC.Comment: 23 pages, 2 figures, submitted to Journal of Optics

Moving Atom-Field Interaction: Correction to Casimir-Polder Effect from Coherent Back-action

The Casimir-Polder force is an attractive force between a polarizable atom and a conducting or dielectric boundary. Its original computation was in terms of the Lamb shift of the atomic ground state in an electromagnetic field (EMF) modified by boundary conditions along the wall and assuming a stationary atom. We calculate the corrections to this force due to a moving atom, demanding maximal preservation of entanglement generated by the moving atom-conducting wall system. We do this by using non-perturbative path integral techniques which allow for coherent back-action and thus can treat non-Markovian processes. We recompute the atom-wall force for a conducting boundary by allowing the bare atom-EMF ground state to evolve (or self-dress) into the interacting ground state. We find a clear distinction between the cases of stationary and adiabatic motions. Our result for the retardation correction for adiabatic motion is up to twice as much as that computed for stationary atoms. We give physical interpretations of both the stationary and adiabatic atom-wall forces in terms of alteration of the virtual photon cloud surrounding the atom by the wall and the Doppler effect.Comment: 16 pages, 2 figures, clarified discussions; to appear in Phys. Rev.

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Online learning can be useful as a means of preparing individual students for assigned readings and study With respect to programmes and modes of operation, engineering colleges and universities will be different in the future. The providers of engineering education will make extensive use of the Internet and powerful computer technologies to define the new methods of distance learning, the alternative methods of delivery of educational content, and the norms and standards for quantity and quality, as well as scale and breadth of online learning In this study, research was undertaken on the use of the Internet for online learning for the students of a regular class taught in a traditional way. A questionnaire was developed in order to establish the availability of computers at home, Learning through technology, using the Internet at home for first year engineering students L.G. Boussiakou † & E.C. Kalkani ‡ King Saud University, Riyadh, Kingdom of Saudi Arabia † National Technical University of Athens, Athens, Greece ‡ ABSTRACT: In the present study, the findings are presented from research that was undertaken for a course for first year students of a technological curriculum. The students were asked about the availability of computers at home, Internet connections, the use of the Internet for education and playing games, the use for access for course materials, and for communication with the instructor. The findings indicate that students can use multiple sites on the Internet, devote different percentages of their study time to online learning, while the availability and the use of the Internet does not predict the grade of the final examination attained for the course. Students also indicated the most popular sites that they use on the Internet, the benefits to their learning from their present use of the Internet and the expected benefits from future use. Based on the above findings, not only do certain university Web sites need re-evaluation to improve their usefulness, but also there needs to be a modification in the teaching of the courses that are available online