Manifestation of superfluidity in an evolving Bose-condensed gas

We study the generation of excitations due to an ''impurity''(static perturbation) placed into an oscillating Bose-condensed gas in the time-dependent trapping field. It is shown that there are two regions for the position of the local perturbation. In the first region the condensate flows around the ''impurity'' without generation of excitations demonstrating superfluid properties. In the second region the creation of excitations occurs, at least within a limited time interval, revealing destruction of superfluidity. The phenomenon can be studied by measuring the damping of condensate oscillations at different positions of the ''impurity''

Possible Quantum Diffusion of Polaronic Muons in Dy2_2Ti2_2O7_7 Spin Ice

We interpret recent measurements of the zero field muon relaxation rate in the frustrated magnetic pyrochlore Dy$_2$Ti$_2$O$_7$ as resulting from the quantum diffusion of muons in the substance. In this scenario, the plateau observed at low temperature ($<7$ K) in the relaxation rate is due to coherent tunneling of the muons through a spatially disordered spin state and not to any magnetic fluctuations persisting at low temperature. Two further regimes either side of a maximum relaxation rate at $T^* = 50$ K correspond to a crossover between tunnelling and incoherent activated hopping motion of the muon. Our fit of the experimental data is compared with the case of muonium diffusion in KCl.Comment: 15 pages, 2 figure

A contextual approach to trauma experience: lessons from life events research

There has been much debate over what constitutes trauma experience and how this is differentiated from other very negative life events in the diagnosis of PTSD. We believe the DSM implication that trauma events are uniquely different from other types of negative life events and are limited to a few specific types of predetermined event identified categorically hinders the utility of current trauma definitions in research and practice. Whilst we do not take issue with the standard definition of trauma events, a binary checklist-style approach to identifying such events has a potential for missing relevant experience. Instead, we argue that trauma events should be considered to be at one end of a continuum of threat/severity, with potential for more or less ‘threat to life’ in a range of domains. Furthermore, a wider assessment of events could elucidate a greater range of co-existing trauma events, those sub-threshold experiences related to phasing of trauma, and other unrelated negative life events which may contribute to context and impact. In this critique of definitions of trauma events we argue that the current definition of PTSD criterion-A events limits their utility in both research and clinical practice. Following intensive life event assessments such as the LEDS (Life Events and Difficulties Schedule) the application of dimensions underlying a cross spectrum of events includes loss (of person, role, plan or ideas about the self), danger (future loss/threat to security), humiliation (devaluation of self/rejection) and entrapment (sense of imprisonment) can be used to further categorise events or trauma, and specify their likely impact. Data is provided of the overlap of ‘markedly’ threatening negative events (using the LEDS) and those constituting trauma using a commonly used checklist in a high-risk community sample of women. This yielded high specificity (97%; CI = 95.60-97.71) but low sensitivity (41%; (95% CI = 27.57-54.97) with around a third rated on both. Most of the trauma events involved loss and danger categorisation and only in one instance humiliation. Other markedly threatening, non-trauma events, involved not only loss and danger but also humiliation and entrapment. We discuss how a more in-depth assessment of trauma events utilising these dimensions and with the new Computerised Life Events Assessment Record (CLEAR), could aid us in our understanding of trauma events and lead to more personalised treatment possibilities

Genuine phase diffusion of a Bose-Einstein condensate in the microcanonical ensemble: A classical field study

Within the classical field model, we find that the phase of a Bose-Einstein condensate undergoes a true diffusive motion in the microcanonical ensemble, the variance of the condensate phase change between time zero and time $t$ growing linearly in $t$. The phase diffusion coefficient obeys a simple scaling law in the double thermodynamic and Bogoliubov limit. We construct an approximate calculation of the diffusion coefficient, in fair agreement with the numerical results over the considered temperature range, and we extend this approximate calculation to the quantum field.Comment: 9 pages, 6 figure

Bound states of three and four resonantly interacting particles

We present an exact diagrammatic approach for the problem of dimer-dimer scattering in 3D for dimers being a resonant bound state of two fermions in a spin-singlet state, with corresponding scattering length $a_F$. Applying this approach to the calculation of the dimer-dimer scattering length $a_B$, we recover exactly the already known result $a_B=0.60 a_F$. We use the developed approach to obtain new results in 2D for fermions as well as for bosons. Namely, we calculate bound state energies for three $bbb$ and four $bbbb$ resonantly interacting bosons in 2D. For the case of resonant interaction between fermions and bosons we calculate exactly bound state energies of the following complexes: two bosons plus one fermion $bbf$, two bosons plus two fermions $bf_{\uparrow}bf_{\downarrow}$, and three bosons plus one fermion $bbbf$.Comment: 10 pages, 9 figure

A priori mixing of mesons and the |Delta I|=1/2 rule in K\to\pi\pi

We consider the hypothesis of a priori mixings in the mass eigenstates of mesons to obtain the |Delta I|=1/2 rule in K\to\pi\pi. The Hamiltonian responsible for the transition is the strong interacting one. The experimental data are described using the isospin symmetry relations between the strong coupling constants

Understanding trauma in children and young people in the school setting

Aim: Educational practitioners are increasingly aware of trauma experiences in students as a factor in child disturbance and schooling problems. This discussion paper aims to clarify definitions of trauma and differentiate them from other adverse childhood experiences (ACE), describe trauma impact in terms of clinical outcomes (PTSD, emotional and behavioural disorder) and how attachment factors mediate risk and discuss the challenges and ethics of identifying and enquiring about trauma experience in a school setting. Rationale: Schools are increasingly required to be 'trauma sensitive' and to intervene where possible, with government requirements of improving mental health in schools. However, this poses a real challenge for educationalists given the barriers due to ethics, stigma/secrecy, referral implications and measurement availability for whole school approaches. Universal screening may provide a framework that helps schools recognise, measure and treat trauma. Findings: A conceptual model clarifying trauma exposure, trauma impact and mediating factors is identified to aid understanding for teachers. Use of technological screening methods for whole school monitoring of trauma impacts, including mediating risks, are outlined. Limitations: A full literature review of trauma or school-based interventions is not provided. Nor are biological impacts of trauma at different developmental stages described. Conclusion: Teachers would benefit from having a psychological understanding of trauma models and their component parts in order to identify what lies within the remit of schools for identification and intervention