Bose-Einstein condensates in `giant' toroidal magnetic traps

The experimental realisation of gaseous Bose-Einstein condensation (BEC) in 1995 sparked considerable interest in this intriguing quantum fluid. Here we report on progress towards the development of an 87Rb BEC experiment in a large (~10cm diameter) toroidal storage ring. A BEC will be formed at a localised region within the toroidal magnetic trap, from whence it can be launched around the torus. The benefits of the system are many-fold, as it should readily enable detailed investigations of persistent currents, Josephson effects, phase fluctuations and high-precision Sagnac or gravitational interferometry.Comment: 5 pages, 3 figures (Figs. 1 and 2 now work

Trans-spectral orbital angular momentum transfer via four-wave mixing in Rb vapor

We report the transfer of phase structure and, in particular, of orbital angular momentum from near-infrared pump light to blue light generated in a four-wave-mixing process in Rb-85 vapor. The intensity and phase profile of the two pump lasers at 780 and 776 nm, shaped by a spatial light modulator, influences the phase and intensity profile of light at 420 nm, which is generated in a subsequent coherent cascade. In particular, we observe that the phase profile associated with orbital angular momentum is transferred entirely from the pump light to the blue. Pumping with more complicated light profiles results in the excitation of spatial modes in the blue that depend strongly on phase matching, thus demonstrating the parametric nature of the mode transfer. These results have implications on the inscription and storage of phase information in atomic gases

A simple extended-cavity diode laser

Operating a laser diode in an extended cavity which provides frequency-selective feedback is a very effective method of reducing the laser's linewidth and improving its tunability. We have developed an extremely simple laser of this type, built from inexpensive commercial components with only a few minor modifications, A 780 nm laser built to this design has an output power of 80 mW, a Linewidth of 350 kHz, and it has been continuously locked to a Doppler-free rubidium transition for several days

A Modified "Bottom-up" Thermalization in Heavy Ion Collisions

In the initial stage of the bottom-up picture of thermalization in heavy ion collisions, the gluon distribution is highly anisotropic which can give rise to plasma instability. This has not been taken account in the original paper. It is shown that in the presence of instability there are scaling solutions, which depend on one parameter, that match smoothly onto the late stage of bottom-up when thermalization takes place.Comment: 8 pages and 1 embedded figure, talk presented at the Workshop on "Quark-Gluon Plasma Thermalization", Vienna, Austria, 10-12 August 200

On the thermodynamic framework of generalized coupled thermoelastic-viscoplastic-damage modeling

A complete potential based framework using internal state variables is put forth for the derivation of reversible and irreversible constitutive equations. In this framework, the existence of the total (integrated) form of either the (Helmholtz) free energy or the (Gibbs) complementary free energy are assumed a priori. Two options for describing the flow and evolutionary equations are described, wherein option one (the fully coupled form) is shown to be over restrictive while the second option (the decoupled form) provides significant flexibility. As a consequence of the decoupled form, a new operator, i.e., the Compliance operator, is defined which provides a link between the assumed Gibb's and complementary dissipation potential and ensures a number of desirable numerical features, for example the symmetry of the resulting consistent tangent stiffness matrix. An important conclusion reached, is that although many theories in the literature do not conform to the general potential framework outlined, it is still possible in some cases, by slight modifications of the used forms, to restore the complete potential structure

Explicit robust schemes for implementation of a class of principal value-based constitutive models: Theoretical development

The issue of developing effective and robust schemes to implement a class of the Ogden-type hyperelastic constitutive models is addressed. To this end, explicit forms for the corresponding material tangent stiffness tensors are developed, and these are valid for the entire deformation range; i.e., with both distinct as well as repeated principal-stretch values. Throughout the analysis the various implications of the underlying property of separability of the strain-energy functions are exploited, thus leading to compact final forms of the tensor expressions. In particular, this facilitated the treatment of complex cases of uncoupled volumetric/deviatoric formulations for incompressible materials. The forms derived are also amenable for use with symbolic-manipulation packages for systematic code generation

Adaptive reflection and focusing of Bose-Einstein condensates

We report adjustable magnetic `bouncing' and focusing of a dilute $^{87}$Rb Bose gas. Both the condensate production and manipulation are realised using a particularly straight-forward apparatus. The bouncing region is comprised of approximately concentric ellipsoidal magnetic equipotentials with a centre that can be adjusted vertically. We extend, and discuss the limitations of, simple Thomas-Fermi and Monte-Carlo theoretical models for the bouncing, which at present find close agreement with the condensate's evolution. Very strong focusing has been inferred and the observation of atomic matter-wave diffraction should be possible. Prospects look bright for applications in matter-wave atom-optics, due to the very smooth nature of the mirror

Investigation of double beta decay with the NEMO-3 detector

The double beta decay experiment NEMO~3 has been taking data since February 2003. The aim of this experiment is to search for neutrinoless ($0\nu\beta\beta$) decay and investigate two neutrino double beta decay in seven different isotopically enriched samples ($^{100}$Mo, $^{82}$Se, $^{48}$Ca, $^{96}$Zr, $^{116}$Cd, $^{130}$Te and $^{150}$Nd). After analysis of the data corresponding to 3.75 y, no evidence for $0\nu\beta\beta$ decay in the $^{100}$Mo and $^{82}$Se samples was found. The half-life limits at the 90% C.L. are $1.1\cdot 10^{24}$ y and $3.6\cdot 10^{23}$ y, respectively. Additionally for $0\nu\beta\beta$ decay the following limits at the 90% C.L. were obtained, $> 1.3 \cdot 10^{22}$ y for $^{48}$Ca, $> 9.2 \cdot 10^{21}$ y for $^{96}$Zr and $> 1.8 \cdot 10^{22}$ y for $^{150}$Nd. The $2\nu\beta\beta$ decay half-life values were precisely measured for all investigated isotopes.Comment: 12 pages, 4 figures, 5 tables; talk at conference on "Fundamental Interactions Physics" (ITEP, Moscow, November 23-27, 2009