Deconfinement and cold atoms in optical lattices

Despite the fact that by now one dimensional and three dimensional systems of interacting particles are reasonably well understood, very little is known on how to go from the one dimensional physics to the three dimensional one. This is in particular true in a quasi-one dimensional geometry where the hopping of particles between one dimensional chains or tubes can lead to a dimensional crossover between a Luttinger liquid and more conventional high dimensional states. Such a situation is relevant to many physical systems. Recently cold atoms in optical traps have provided a unique and controllable system in which to investigate this physics. We thus analyze a system made of coupled one dimensional tubes of interacting fermions. We explore the observable consequences, such as the phase diagram for isolated tubes, and the possibility to realize unusual superfluid phases in coupled tubes systems.Comment: Proceedings of the conference on "Quantum Many Body Theories 13", to be published by World Scientifi

Small polarons in dilute gas Bose-Einstein condensates

A neutral impurity atom immersed in a dilute Bose-Einstein condensate (BEC) can have a bound ground state in which the impurity is self-localized. In this small polaron-like state, the impurity distorts the density of the surrounding BEC, thereby creating the self-trapping potential minimum. We describe the self-localization in a strong coupling approach

Conditional choice modelling of time allocation among spouses in transport settings : theory and empirical findings

As part of a wider rule-based model of activity behaviour, this paper explores the possibility to build a suite of linked conditional choice models to predict the amount of time spouses in a household spend on a set of activities together and alone. First, a choice model is used to predict the probability and hence the amount of time the spouses spend together and alone. Conditional on the outcome of this choice model, a second model predicts the amount of time that is spent by each spouse separately on a set of activities, as a function of socio-demographics, car availability and work status. The model is estimated using a small sample in Hendrik-Ido-Ambacht and Zwijndrecht in the Netherlands. The results indicate the model to have face validity. Rho-square values are also high

The π+\pi^+--emission puzzle in Λ4^4_\LambdaHe decay

We re-examine the puzzling $\pi^+$ emission from the weak decay of $^4_\Lambda$He and propose an explanation in terms of a three-body decay of the virtual $\Sigma^+$. Such a resolution of the $\pi^+$ decay puzzle is consistent with the calculated $\Sigma^+$ probability in light $\Lambda$ hypernuclei as well as the experimentally observed $\pi^+$ energy spectrum and $s$--wave angular distribution.Comment: 16 pages, Revtex, 2 figures, amstex and amssymb style file