22 research outputs found
Negative Differential Conductivity in an Interacting Quantum Gas
No full textNegative differential conductivity (NDC) is a widely exploited mechanism in many areas of research dealing with particle and energy transport. We experimentally realize such a many body quantum transport system based on ultracold atoms in a periodic potential. We prepare our system by loading Bose condensed rubidium atoms in a 1D optical lattice with high atom occupancy per lattice site. Subsequently, we remove all the atoms from a central lattice site. While the atoms from neighboring sites tunnel into the empty site, we observe NDC in the resulting current voltage characteristics and investigate the microscopic mechanism behind it [R. Labouvie, B. Santra, S. Heun, S. Wimberger, H. Ott, arXiv:1411.5632]
Psyche and Eros
No full textIn Psyche and Eros, first published in 1994, Gisela Labouvie-Vief describes historical and current concepts of mind and development, drawing from disciplines as diverse as philosophy, mythology, religion, literature, and psychology. She then presents a powerful theory of the maturing of mind, which brings together her empirical work and her exploration into mythology. The classical Greek myth of the gods Psyche and Eros serves as an evocative illustration of the author's theory. Psyche and Eros asserts that the core experience of development differs along gender lines. Rationality is regarded as masculine, while imagination is viewed as feminine. Competition between 'masculine' and 'feminine' parts of the mind has limited our ability to describe the mind and its development over the life course, just as it limits our experiences of development as men and women. The author suggests that we overcome the dualistic way of thinking about mind, and see how rationality and imagination can complement each other.</jats:p
Parametrisches Heizen in optischen Gittern und Charakterisierung eines akusto-optischen Deflektors für die Erzeugung von zeitgemittelten Potentialen
No full textLooking Inside the Black Box of "Attendance at Services": New Measures for Exploring an Old Dimension in Religion and Health Research
No full textResearch in religion and health has spurred new interest in measuring religiousness. Measurement efforts have focused on subjective facets of religiousness such as spirituality and beliefs, and less attention has been paid to congregate aspects, beyond the single item measuring attendance at services. We evaluate some new measures for religious experiences occurring during congregational worship services. Respondents (N=576) were religiously-diverse community dwelling adults interviewed prior to cardiac surgery. Exploratory factor analysis of the new items with a pool of standard items yielded a readily interpretable solution, involving seven correlated but distinct factors and one index variable, with high levels of internal consistency. We describe religious affiliation and demographic differences in these measures. Attendance at religious services provides multifaceted physical, emotional, social, and spiritual experiences that may promote physical health through multiple pathways.This research was supported by grants from the National Institute on Aging (AG15160 and AG16750, Richard Contrada, PI).Published 2009 in International Journal for the Psychology of Religion at http://www.informaworld.com/smpp/content~db=all~content=a907482564~frm=titlelin
Initial classmate acceptance reduces freshman year decline in sense of school belonging among urban high school students
No full textAlthough research has examined the positive outcomes associated with sense of school belonging, relatively little empirical attention has been given to identifying the variables that influence or contribute to sense of belonging. There is some evidence from cross-sectional studies of middle school students that academic performance correlates with sense of school belonging. Furthermore, perceived classmate acceptance explained a significant amount of the variance in sense of belonging in one sample of middle schoolers. It is not yet clear, however, if (1) these relationships generalize to older students, and (2) if one or both of those correlates prospectively predict sense of school belonging during the key freshman year transitional period. A further question worth examining is if academic performance and perceived classmate acceptance prospectively predict sense of school belonging better than the reverse temporal sequencing (e.g., beginning of the year sense of belonging as a predictor of end of the year academic performance and classmate acceptance). The current study examined these questions in a sample of Black and Latino urban high school freshmen. Consistent with past research with younger and older adolescents, sense of school belonging declined over the course of the year in our sample of high school freshmen. With regard to predictive relations, perceived classmate acceptance, but not academic performance, prospectively predicted end of year sense of school belonging, after controlling for initial levels of sense of belonging. Furthermore, when the reverse temporal sequencing of these variables was tested, sense of school belonging did not prospectively predict perceived classmate acceptance. These findings suggest that the positive relation between perceived classmate acceptance and sense of school belonging generalizes from younger adolescents (middle schoolers) to older adolescents (high school freshmen). Although no conclusions regarding causality can be drawn from our brief longitudinal study of Black and Latino high school freshmen, given that perceived classmate acceptance prospectively predicted end of year sense of school belonging, and the lack of support for the reverse temporal sequence, the role of perceived classmate acceptance in the development and/or maintenance of sense of school belonging during the key transition into high school warrants further empirical attention.Ph.D.Includes bibliographical references (p. 29-31)
Dimensional phase transition from an array of 1D Luttinger liquids to a 3D Bose-Einstein condensate
No full textWe study the thermodynamic properties of a 2D array of coupled one-dimensional Bose gases. The system is realized with ultracold bosonic atoms loaded in the potential tubes of a two-dimensional optical lattice. For negligible coupling strength, each tube is an independent weakly interacting 1D Bose gas featuring Tomonaga Luttinger liquid behavior. By decreasing the lattice depth, we increase the coupling strength between the 1D gases and allow for the phase transition into a 3D condensate. We extract the phase diagram for such a system and compare our results with theoretical predictions. Because of the high effective mass across the periodic potential and the increased 1D interaction strength, the phase transition is shifted to large positive values of the chemical potential. Our results are prototypical to a variety of low-dimensional systems, where the coupling between the subsystems is realized in a higher spatial dimension such as coupled spin chains in magnetic insulators.</p
Spatiotemporal fermionization of strongly interacting one-dimensional bosons
No full textBuilding on the recent experimental achievements obtained with scanning electron microscopy on ultracold atoms, we study one-dimensional Bose gases in the crossover between the weakly (quasicondensate) and the strongly interacting (Tonks-Girardeau) regime. We measure the temporal two-particle correlation function and compare it with calculations performed using the time-evolving block decimation algorithm. More pronounced antibunching is observed when entering the more strongly interacting regime. Even though this mimics the onset of a fermionic behavior, we highlight that the exact and simple duality between one-dimensional bosons and fermions does not hold when such a dynamical response is probed. The onset of fermionization is also reflected in the density distribution, which we measure in situ to extract the relevant parameters and to identify the different regimes. Our results show agreement between experiment and theory and give insight into the dynamics of strongly correlated many-body systems.</p
Thermodynamics of strongly correlated one-dimensional Bose gases
No full textWe investigate the thermodynamics of one-dimensional (1D) Bose gases in the strongly correlated regime. To this end, we prepare ensembles of independent 1D Bose gases in a two-dimensional optical lattice and perform high-resolution in situ imaging of the column-integrated density distribution. Using an inverse Abel transformation we derive effective one-dimensional line-density profiles and compare them to exact theoretical models. The high resolution allows for a direct thermometry of the trapped ensembles. The knowledge about the temperature enables us to extract thermodynamic equations of state such as the phase-space density, the entropy per particle, and the local pair-correlation function.</p
Measuring finite-range phase coherence in an optical lattice using Talbot interferometry
No full textAbstractOne of the important goals of present research is to control and manipulate coherence in a broad variety of systems, such as semiconductor spintronics, biological photosynthetic systems, superconducting qubits and complex atomic networks. Over the past decades, interferometry of atoms and molecules has proven to be a powerful tool to explore coherence. Here we demonstrate a near-field interferometer based on the Talbot effect, which allows us to measure finite-range phase coherence of ultracold atoms in an optical lattice. We apply this interferometer to study the build-up of phase coherence after a quantum quench of a Bose–Einstein condensate residing in a one-dimensional optical lattice. Our technique of measuring finite-range phase coherence is generic, easy to adopt and can be applied in practically all lattice experiments without further modifications.</jats:p
