Dynamical instability of a spin spiral in an interacting Fermi gas as a probe of the Stoner transition

We propose an experiment to probe ferromagnetic phenomena in an ultracold Fermi gas, while alleviating the sensitivity to three-body loss and competing many-body instabilities. The system is initialized in a small pitch spin spiral, which becomes unstable in the presence of repulsive interactions. To linear order the exponentially growing collective modes exhibit critical slowing down close to the Stoner transition point. Also, to this order, the dynamics are identical on the paramagnetic and ferromagnetic sides of the transition. However, we show that scattering off the exponentially growing modes qualitatively alters the collective mode structure. The critical slowing down is eliminated and in its place a new unstable branch develops at large wave vectors. Furthermore, long-wavelength instabilities are quenched on the paramagnetic side of the transition. We study the experimental observation of the instabilities, specifically addressing the trapping geometry and how phase-contrast imaging will reveal the emerging domain structure. These probes of the dynamical phenomena could allow experiments to detect the transition point and distinguish between the paramagnetic and ferromagnetic regimes

Cross-validation of the body compassion scale in a sample of women in perimenopause.

This study is a cross-validation of the Body Compassion Scale (BCS) to confirm its factor structure and to assess concurrent validity in women in perimenopause. Body compassion is a construct developed by the author referring to the level of compassion with which an individual relates to her body. It is based in contemporary mindfulnessand acceptance-based conceptual models. The body is central to the experience of women in perimenopause. Moreover, this important transition has been largely medicalized— with little attention given to experiential aspects of this natural phase of life. A total of 281 women in perimenopause completed online questionnaires assessing their experience of key symptoms/characteristics of perimenopause, body image, and mindfulness- and acceptance-based characteristics, including body compassion. Confirmatory factor analysis of the previously identified three factor solution was performed using structural equation modeling. Overall, results showed good fit to the data. The present study provides support for continued use and application of the BCS as a reliable and valid measure of body compassion. Body compassion may provide an assessment that more accurately captures and addresses the experience of relating to one’s body than is currently available. Body compassion in women in perimenopause is described and recommendations for future research directions are provided

Oscillating Superfluidity of Bosons in Optical Lattices

We follow up on a recent suggestion by C. Orzel et. al., Science, 291, 2386 (2001), whereby bosons in an optical lattice would be subjected to a sudden parameter change from the Mott to the superfluid phase. We analyze the Bose Hubbard model with a modified coherent states path integral which can escribe - both - phases. The saddle point theory yields collective oscillations of the uniform superfluid order parameter. These would be seen in time resolved interference patterns made by the released gas. We calculate the collective oscillation's damping rate by phason pair emission. In two dimensions the overdamped region largely overlaps with the quantum critical region. Measurements of critical dynamics on the Mott side are proposed.Comment: 4 pages 1 eps figures; Final version as appears in PRL. Added discussion on spontaneous generation of vortice

The efficacy of problem-solving treatments after deliberate self-harm: meta-analysis of randomized controlled trials with respect to depression, hopelessness and improvement in problems

Background. Brief problem-solving therapy is regarded as a pragmatic treatment for deliberate self-harm (DSH) patients. A recent meta-analysis of randomized controlled trials (RCTs) evaluating this approach indicated a trend towards reduced repetition of DSH but the pooled odds ratio was not statistically significant. We have now examined other important outcomes using this procedure, namely depression, hopelessness and improvement in problems. Method. Six trials in which problem-solving therapy was compared with control treatment were identified from an extensive literature review of RCTs of treatments for DSH patients. Data concerning depression, hopelessness and improvement in problems were extracted. Where relevant statistical data (e.g. standard deviations) were missing these were imputed using various statistical methods. Results were pooled using meta-analytical procedures. Results. At follow-up, patients who were offered problem-solving therapy had significantly greater improvement in scores for depression (standardized mean difference =[minus sign]0·36; 95% CI [minus sign]0·61 to [minus sign]0·11) and hopelessness (weighted mean difference =[minus sign]3·2; 95% CI [minus sign]4·0 to [minus sign]2·41), and significantly more reported improvement in their problems (odds ratio = 2·31; 95% CI 1·29 to 4·13), than patients who were in the control treatment groups. Conclusions. Problem-solving therapy for DSH patients appears to produce better results than control treatment with regard to improvement in depression, hopelessness and problems. It is desirable that this finding is confirmed in a large trial, which will also allow adequate testing of the impact of this treatment on repetition of DSH

Constrained Cost-Coupled Stochastic Games with Independent State Processes

We consider a non-cooperative constrained stochastic games with N players with the following special structure. With each player there is an associated controlled Markov chain. The transition probabilities of the i-th Markov chain depend only on the state and actions of controller i. The information structure that we consider is such that each player knows the state of its own MDP and its own actions. It does not know the states of, and the actions taken by other players. Finally, each player wishes to minimize a time-average cost function, and has constraints over other time-avrage cost functions. Both the cost that is minimized as well as those defining the constraints depend on the state and actions of all players. We study in this paper the existence of a Nash equilirium. Examples in power control in wireless communications are given.Comment: 7 pages, submitted in september 2006 to Operations Research Letter

Employment implications of the growth of the Indigenous Australian working-age population to 2001

This paper has been specifically prepared as a submission to the review of the Aboriginal Employment Development Policy (AEDP) which is to be completed early in 1994. A critical innovative feature of the Commonwealth Government's AEDP, launched in 1986-87, is its overarching goal of attaining statistical employment equality between Indigenous and non-Indigenous Australians by the year 2000. This paper examines the nature of labour force planning and goal setting in the AEDP Statement. It then re-examines a critique of the statistical targets made by demographers Tesfaghiorghis and Gray in 1991. Using recently published 1991 Census data, the paper explores intercensal changes in the size and labour force status of the Indigenous population. The paper's main aim is to present new projections of the Indigenous population of working age to the year 2001 and to re-assess the employment creation goals that will need to be set if statistical equality is to be achieved. It is estimated that the Indigenous population of working age will exceed 200,000 by the year 2001 and that to achieve statistical equality between 6,400 and 7,400 new jobs per annum will need to be created. Both figures represent over 10 per cent of the 1991 base employment of Indigenous Australians and represent impossible targets. The paper highlights a number of statistical, methodological and conceptual issues. In particular, it emphasises that insufficient statistical data are available to make accurate projections and that a more sophisticated analytical framework is required. At the macro level, it will be essential to match the supply of Indigenous labour, in all its diversity, with regional demand. Given significant underestimation in initial AEDP goal-setting, the paper concludes that the aim of statistical equality may be both inappropriate and destined to fail and that a notion of equity that recognises diversity of both circumstances and aspirations is needed

Establishing trends in ATSIC regional council populations using census data: A cautionary note

Section 94(1) of the Aboriginal and Torres Strait Islander Act 1989 requires regional councils to 'formulate and revise from time to time a regional plan for improving the economic, social and cultural status of Aboriginal and Torres Strait Islander residents of the region'. Guidelines for the preparation of such regional plans require that councils compile a data base on the demographic composition of their council area and to consider how various social indicators may differ in the future, say in the next five years. While not explicitly stated, the guidelines thus require that some form of demographic trend analysis be undertaken for council areas so that meaningful projections of the population to be serviced may be calculated. This paper seeks to point out that limitations in official census data for Aborigines and Torres Strait Islanders draw into question the validity of trend analysis based on time series data for regional council areas. Accordingly, the meaningful application of projection techniques to estimate future population profiles using existing census data is severely restricted. Among the difficulties encountered in reconstructing council area populations are, census boundary changes over time, changes in enumeration techniques and coverage, the problems posed by self-identification and associated population growth, and, in some cases, the difficulty of matching ATSIC regional council boundaries with census geography. Following discussion of these problems, detailed figures showing changes in the size of the Aboriginal and Islander populations and labour force in each council area are presented using 1976 as the base year. As expected, geographic patterns of population and labour force change are difficult to discern and exact reasons for comparative growth or decline are impossible to determine. The paper concludes that reverse projections for regional council areas using 1991 Census data would provide a more reliable basis for establishing demographic trends. Although not entirely adequate, these reconstructions for ATSIC regional councils are the only estimates of these populations that have been undertaken to date

Hanbury Brown-Twiss Interferometry for Fractional and Integer Mott Phases

Hanbury-Brown-Twiss interferometry (HBTI) is used to study integer and fractionally filled Mott Insulator (MI) phases in period-2 optical superlattices. In contrast to the quasimomentum distribution, this second order interferometry pattern exhibits high contrast fringes in the it insulating phases. Our detailed study of HBTI suggests that this interference pattern signals the various superfluid-insulator transitions and therefore can be used as a practical method to determine the phase diagram of the system. We find that in the presence of a confining potential the insulating phases become robust as they exist for a finite range of atom numbers. Furthermore, we show that in the trapped case the HBTI interferogram signals the formation of the MI domains and probes the shell structure of the system.Comment: 13 pages, 15 figure