Semi-classical Analysis of Spin Systems near Critical Energies

The spectral properties of $su(2)$ Hamiltonians are studied for energies near the critical classical energy $\varepsilon_c$ for which the corresponding classical dynamics presents hyperbolic points (HP). A general method leading to an algebraic relation for eigenvalues in the vicinity of $\varepsilon_c$ is obtained in the thermodynamic limit, when the semi-classical parameter $n^{-1}=(2s)^{-1}$ goes to zero (where $s$ is the total spin of the system). Two applications of this method are given and compared with numerics. Matrix elements of observables, computed between states with energy near $\varepsilon_c$, are also computed and shown to be in agreement with the numerical results

Dissipation-induced long-range order in the one-dimensional Bose-Hubbard model

Understanding the stability of strongly correlated phases of matter when coupled to environmental degrees of freedom is crucial for identifying the conditions under which these states may be observed. Here, we focus on the paradigmatic one-dimensional Bose-Hubbard model, and study the stability of the Luttinger liquid and Mott insulating phases in the presence of local particle exchange with site-independent baths of non-interacting bosons. We perform a numerically exact analysis of this model by adapting the recently developed wormhole quantum Monte Carlo method for retarded interactions to a continuous-time formulation with worm updates; we show how the wormhole updates can be easily implemented in this scheme. For an Ohmic bath, our numerical findings confirm the scaling prediction that the Luttinger-liquid phase becomes unstable at infinitesimal bath coupling. We show that the ensuing phase is a long-range ordered superfluid with spontaneously-broken U(1) symmetry. While the Mott insulator remains a distinct phase for small bath coupling, it exhibits diverging compressibility and non-integer local boson occupation in the thermodynamic limit. Upon increasing the bath coupling, this phase undergoes a transition to a long-range ordered superfluid. Finally, we discuss the effects of super-Ohmic dissipation on the Luttinger-liquid phase. Our results are compatible with a stable dissipative Luttinger-liquid phase that transitions to a long-range ordered superfluid at a finite system-bath coupling.Comment: 16 pages, 15 figure

Positive Psychology and Aging through Heudonic and Eudaimonic Perspectives

Rowe and Kahn’s (1997) version of successful aging defines avoid- ance of disease and disability, maintenance of high physical and cogni- tive function, and sustained engagement in social and productive activ- ities as essential components of aging successfully. The applicability of this model in very advanced age has been questioned and the relative importance of these aspects to well-being is not properly established. In order to analyze the effect of Rowe and Kahn’ criteria on both subjective (hedonic) and psychological (eudaimonic) well-being, 140 individu- als with 100 and more years old from the Oporto Centenarian Study (PT100) were interviewed. The mean age of the sample was 101.18 (SD 1.59); 89.3% women, 76.4% widowed and 57.9% living in the com- munity. The Positive Valuation of Life Scale (Lawton et al., 2001), the Satisfaction with Life Scale (Diener et al., 1985) and a questionnaire of health and social information were used for data collection. Descriptive and inferential analyses were conducted. Mean scores of well-being were 27.81 (SD=5.21) for VOL and 6.51 (SD=1.97) for SWLS. Of the successful aging criteria only social engagement, i.e. participation in social activities, had a significant association with psychological well-being (p<0.01). These results stress out the influence of activity and social engagement participation in the adaptation to the challenges of very old age. The characteristics, sort and distribution of activities practiced at this age should be further investigated in order to promote and/or adjust available social engagement opportunities.info:eu-repo/semantics/publishedVersio

Quantum-Cops: When Communities of Practice Resemble Physics

This paper puts forwards a new way to view how Communities of Practice (CoPs) form in environments that make heavy use of information systems. It uses a concept from Physics to suggest a new type of CoP that can exist in workplaces. In order to do that, the paper uses a simplified taxonomy for CoPs to outline the \u27Quantum-CoPs\u27. These Communities are discussed regarding their behaviour and characteristics, and their potential use as fully developed CoPs. The paper presents some preliminary findings from a semi-structured interview conducted in The Higher Education Academy Psychology Network (UK). These findings are contrasted against the theory discussed and some additional proposals are suggested at the end

Flow structure beneath rotational water waves with stagnation points

The purpose of this work is to explore in detail the structure of the interior flow generated by periodic surface waves on a fluid with constant vorticity. The problem is mapped conformally to a strip and solved numerically using spectral methods. Once the solution is known, the streamlines, pressure and particle paths can be found and mapped back to the physical domain. We find that the flow beneath the waves contains zero, one, two or three stagnation points in a frame moving with the wave speed, and describe the bifurcations between these flows. When the vorticity is sufficiently strong, the pressure in the flow and on the bottom boundary also has very different features from the usual irrotational wave case.</p

What about the Portuguese oldest old? A global overview using census data

Background The older population is itself aging, and achieving an advanced age is becoming more common worldwide. In Portugal, individuals aged 80+ represent 5.6 % of the total population and 26.5 % of the popu- lation were aged 65 and over in 2011. Having a national profile on this population will give important information to develop interven- tion programs and identify the areas requiring most attention. Ob- jective: This study aims to provide a profile of the Portuguese oldest old, as given by the last national census data. Methods The characteristics of all residents aged 80+ (N = 532,219) were ana- lysed considering socio-demographic information (gender, marital status, education, type of residence, place of birth, income) and the existence of difficulties in functional, sensorial and cognitive activities due to health problems or ageing. Results The majority of the most aged are females (64.5 %), widowed (53.9 %), and present low educational levels (46.1 % never attended school and 31.6 % do not know how to read/write). Own pensions constitute the main source of income (96.3 %) and the majority live in private households (88.8 %), with 43.2 % currently living in the place where they were born. The majority (73.0 %) reported major difficulties in at least one functional activity – bathing/dressing, walk- ing/climbing stairs, seeing, hearing, memory/concentration, under- standing others/being understood. Conclusions The high percentage of oldest old living in private households and the presence of functional limitations point to the importance of in- formal care and community care services to support this population. Further studies paying attention to their needs and utilisation of ser- vices are required.info:eu-repo/semantics/publishedVersio

Being successful aged at one hundred years old: alternative and subjective criteria

Age, i.e. being younger, has been the most consistent predictor of successful aging, indicating a dramatic drop of the rate of success with advancing age. However, emergent studies based on expanded psychological concepts have been revealing the admirable capacity of oldest old individuals to overcome adversities and adapting to the challenges of very advanced age. This study aims to explore alternative criteria to Rowe and Kahn successful aging model in centenarians. A sample of 70 individuals (Mage100.91, SD 1.37, 87.1%female) with cognitive capacity for answering self-report questions were selected from the population-based Oporto Centenarian Study (PT100). Perceived economic status, sub- jective health and happiness were considered as components to assess successful aging. Main findings revealed that 62.9% of the sample was able to meet economic needs, 44.3% was happy and 32.3% reported a positive self-perception of health. 12.9% of the participants satisfied all three criteria and 16.1% didnt fulfilled any. A previous study using the same alternative criteria found that 47.5% of centenarians were successful aged, whereas none of them satisfied all three objective components from Rowe and Kahn’s success- ful aging model (Cho et al., 2012). Thus, the higher propor- tion of centenarians with positive self-ratings demonstrate that they may feel successful despite not being objectively considered as so. The alternative criteria of perceived eco- nomic status, subjective health and happiness considered in this study seem to be suitable to approach successful aging in very advanced age.info:eu-repo/semantics/publishedVersio