Quantum dynamics of a binary mixture of BECs in a double well potential: an Holstein-Primakoff approach

We study the quantum dynamics of a binary mixture of Bose-Einstein condensates (BEC) in a double-well potential starting from a two-mode Bose-Hubbard Hamiltonian. Focussing on the regime where the number of atoms is very large, a mapping onto a SU(2) spin problem together with a Holstein-Primakoff transformation is performed. The quantum evolution of the number difference of bosons between the two wells is investigated for different initial conditions, which range from the case of a small imbalance between the two wells to a coherent spin state. The results show an instability towards a phase-separation above a critical positive value of the interspecies interaction while the system evolves towards a coherent tunneling regime for negative interspecies interactions. A comparison with a semiclassical approach is discussed together with some implications on the experimental realization of phase separation with cold atoms.Comment: 12 pages, 7 figures, accepted for publication in J. Phys.

Computation of the Modes of Elliptic Waveguides with a Curvilinear 2D Frequency-Domain Finite-Difference Approach

A scalar Frequency-Domain Finite-Difference approach to the mode computation of elliptic waveguides is presented. The use of an elliptic cylindrical grid allows us to take exactly into account the curved boundary of the structure and a single mesh has been used both for TE and TM modes. As a consequence, a high accuracy is obtained with a reduced computational burden, since the resulting matrix is highly sparse

Quantum Bose Josephson Junction with binary mixtures of BECs

We study the quantum behaviour of a binary mixture of Bose-Einstein condensates (BEC) in a double-well potential starting from a two-mode Bose-Hubbard Hamiltonian. We focus on the small tunneling amplitude regime and apply perturbation theory up to second order. Analytical expressions for the energy eigenvalues and eigenstates are obtained. Then the quantum evolution of the number difference of bosons between the two potential wells is fully investigated for two different initial conditions: completely localized states and coherent spin states. In the first case both the short and the long time dynamics is studied and a rich behaviour is found, ranging from small amplitude oscillations and collapses and revivals to coherent tunneling. In the second case the short-time scale evolution of number difference is determined and a more irregular dynamics is evidenced. Finally, the formation of Schroedinger cat states is considered and shown to affect the momentum distribution.Comment: 14 pages, 4 figure

An IRAS High Resolution Image Restoration (HIRES) Atlas of All Interacting Galaxies in the IRAS Revised Bright Galaxy Sample

We present high-resolution (30"-1') 12, 25, 60, and 100 micron images of 106 interacting galaxy systems contained in the IRAS Revised Bright Galaxy Sample (RBGS, Sanders et al. 2003), a complete sample of all galaxies having a 60 micron flux density greater than 5.24 Jy. These systems were selected to have at least two distinguishable galaxies separated by less than three average galactic diameters, and thus we have excluded very widely separated systems and very advanced mergers. The new complete survey has the same properties as the prototype survey of Surace et al. 1993. We find no increased tendency for infrared-bright galaxies to be associated with other infrared bright galaxies among the widely separated pairs studied here. We find small enhancements in far-infrared activity in multiple galaxy systems relative to RBGS non-interacting galaxies with the same blue luminosity distribution. We also find no differences in infrared activity (as measured by infrared color and luminosity) between late and early-type spiral galaxies.Comment: 49 pages, 13 figures. To appear in the Astronomical Journal. Figures have been degraded due to space considerations. A PDF version with higher quality figures is available at http://humu.ipac.caltech.edu/~jason/pubs/surace_hires.pd

Massive Quantum Memories by Periodically Inverted Dynamic Evolutions

We introduce a general scheme to realize perfect quantum state reconstruction and storage in systems of interacting qubits. This novel approach is based on the idea of controlling the residual interactions by suitable external controls that, acting on the inter-qubit couplings, yield time-periodic inversions in the dynamical evolution, thus cancelling exactly the effects of quantum state diffusion. We illustrate the method for spin systems on closed rings with XY residual interactions, showing that it enables the massive storage of arbitrarily large numbers of local states, and we demonstrate its robustness against several realistic sources of noise and imperfections.Comment: 10 pages, 3 figures. Contribution to the Proceedings of the Workshop on "Quantum entanglement in physical and information sciences", held in Pisa, December 14-18, 200

Experimental investigation of the steady state behaviour of Breathing Walls by means of a novel laboratory apparatus

Breathing Walls are envelope components, based on porous materials, crossed by a natural or forced airflow. Since they behave both as recovery heat exchangers and active insulation, reducing the conductive heat flux, they represent a promising envelope technology, allowing to reduce energy consumption in buildings. From the modeling point of view, an analytical model can be found in literature, describing heat and mass transfer across Breathing Walls in steady state conditions. However, to the best of the authors' knowledge, the model lacks an exhaustive experimental validation. Therefore, in this paper, the novel laboratory apparatus named Dual Air Vented Thermal Box developed at Politecnico of Milano is presented. The apparatus is used to experimentally investigate the steady state behaviour of a 1 m2 Air Permeable Concrete sample, crossed by an airflow at different velocities up to 12 mm/s. The temperature profile inside the sample, measured in different positions, is compared with the model predictions. While in the central portion of the wall a very good agreement is found, the experimental results at the top and at the bottom of the wall suggest a non-uniform velocity field entering the sample. A qualitative confirmation of this hypothesis is provided by CFD simulations on the apparatus, clearly showing a mixed convection regime on both sides of the wall. The results lead to state the validity of the one-dimensional analytical model in literature, although a careful application should take into account adjusted boundary conditions, consisting in an airflow velocity possibly variable with height

Evidences for a quasi 60-year North Atlantic Oscillation since 1700 and its meaning for global climate change

The North Atlantic Oscillation (NAO) obtained using instrumental and documentary proxy predictors from Eurasia is found to be characterized by a quasi 60-year dominant oscillation since 1650. This pattern emerges clearly once the NAO record is time integrated to stress its comparison with the temperature record. The integrated NAO (INAO) is found to well correlate with the length of the day (since 1650) and the global surface sea temperature record HadSST2 and HadSST3 (since 1850). These findings suggest that INAO can be used as a good proxy for global climate change, and that a 60-year cycle exists in the global climate since at least 1700. Finally, the INAO ~60-year oscillation well correlates with the ~60- year oscillations found in the historical European aurora record since 1700, which suggests that this 60-year dominant climatic cycle has a solar-astronomical origin

Content analysis of children's programs on Boston's television stations

Thesis (Ed.M.)--Boston Universit

QBO of the Equatorial-Stratospheric Winds Revisited: New methods to verify the dominance of 28-month cycle

The equatorial-stratospheric wind that shows a Quasi Biennial Oscillation (22-32 months) has been revisited using a dual statistical detail regarding the search of the dominance harmonics. Data were used from the Freie Universitat of Berlin since 1953 for different heights combining the observations of the three radiosonde stations. The dominant period of 28 months has been reaffirmed but with a discernible amplitude and a phase, respectively, inversely varying with height. Such a cycle suggests an estimate for the coming easterly equatorial wind occurrence at 15 hPa level at the end of 2009. The 28-month harmonic is found to take about a year to descend from 15 to 70 hPa with a progressive lag of about 1 month/km. At the top of the stratosphere, easterlies dominate, while at the bottom, westerlies are more likely to be found. Correlation with sunspot numbers and seasonal rainfall is discussed

Resolved CO(1-0) Nuclei in IRAS 14348-1447: Evidence for Massive Bulge Progenitors to Ultraluminous Infrared Galaxies

High-resolution, CO(1-0) interferometry of the ultraluminous infrared galaxy IRAS 14348-1447 is presented. The merger system has a molecular gas mass of \~3x10^10 solar masses and a projected nuclear separation of 4.8 kpc (3.5"), making it one of the most molecular gas-rich galaxies known and an ideal candidate for studying the intermediate stages of an ultraluminous merger event. The CO morphology shows two molecular gas components associated with the stellar nuclei of the progenitors, consistent with the idea that the molecular disks are gravitationally bound by the dense bulges of the progenitor galaxies as the interaction proceeds. In contrast, less luminous infrared galaxies observed to date with projected nuclear separations of ~<5 kpc show a dominant CO component between the stellar nuclei. This discrepancy may be an indication that the progenitors of mergers with lower infrared luminosity do not possess massive bulges, and that the gas is stripped during the initial encounter of their progenitors. A comparison of the CO and radio luminosities of the NE and SW component show them to have comparable radio and CO flux ratios of f(NE)/f(SW) ~0.6, possibly indicating that the amount of star-forming molecular gas in the progenitors is correlated with the supernovae rate. The estimate of molecular gas masses of the nuclei and the extent of the radio emission are used to infer that the nuclei of IR 14348-1447 have gas densities comparable to the cores of elliptical galaxies.Comment: LaTex, 5 pages with 1 postscript and 1 jpg figure, ApJ Letters, in pres