3,548 research outputs found
Real-time path integral approach to nonequilibrium many-body quantum system
A real-time path integral Monte Carlo approach is developed to study the
dynamics in a many-body quantum system until reaching a nonequilibrium
stationary state. The approach is based on augmenting an exact reduced equation
for the evolution of the system in the interaction picture which is amenable to
an efficient path integral (worldline) Monte Carlo approach. Results obtained
for a model of inelastic tunneling spectroscopy reveal the applicability of the
approach to a wide range of physically important regimes, including high
(classical) and low (quantum) temperatures, and weak (perturbative) and strong
electron-phonon couplings.Comment: 5 pages, 2 figure
Atmospheric Electricity Problems
The problems encountered when protecting rockets and launch operations from the dangers of lightning are discussed. This reveals the need for a mesoscale network for observing important parameters that indicate lightning danger, as well as the need to develop a set of rules for forecasting potential lightning danger. Before developing methods to inhibit the generation of electricity inside thunderclouds, it is imperative that the charge seperation mechanism be thoroughly understood. The present state-of-the-art of lightning suppression uses either metallic chaff fibers to produce a continuous discharge current or rocket propelled projectiles to discharge the thundercloud with artificially triggered lightning
Dissipative Dynamics with Trapping in Dimers
The trapping of excitations in systems coupled to an environment allows to
study the quantum to classical crossover by different means. We show how to
combine the phenomenological description by a non-hermitian Liouville-von
Neumann Equation (LvNE) approach with the numerically exact path integral
Monte-Carlo (PIMC) method, and exemplify our results for a system of two
coupled two-level systems. By varying the strength of the coupling to the
environment we are able to estimate the parameter range in which the LvNE
approach yields satisfactory results. Moreover, by matching the PIMC results
with the LvNE calculations we have a powerful tool to extrapolate the
numerically exact PIMC method to long times.Comment: 5 pages, 2 figure
Laser spectroscopy and cooling of Yb+ ions on a deep-UV transition
We perform laser spectroscopy of Yb+ ions on the 4f14 6s 2S_{1/2} - 4f13 5d
6s 3D[3/2]_{1/2} transition at 297 nm. The frequency measurements for 170Yb+,
172Yb+, 174Yb+, and 176Yb+ reveal the specific mass shift as well as the field
shifts. In addition, we demonstrate laser cooling of Yb+ ions using this
transition and show that light at 297 nm can be used as the second step in the
photoionization of neutral Yb atoms
Migration and health: Moving towards diversity-oriented public health monitoring at the Robert Koch Institute
Summarizing categories, such as migration background or history of migration, do not reflect the diversity and heterogeneity of the population living in Germany and their health.
A differentiated description of the health situation of people with a history of migration should consider migrationrelated, social, and structural determinants of health as well as their interactions.
The findings obtained in the 'Improving Health Monitoring in Migrant Populations (IMIRA)' projects will help to improve the inclusion of people with a history of migration in future studies as well as in the RKI panel. This will enable an adequate description of the health situation of people with a history of migration and therefore of the general population in Germany.
In future studies, the health status of people who have not been well included in health surveys so far, such as people who are not listed at the registration office, should be monitored. For this purpose, continuous development of sampling and survey methods is necessary
Background Simulations of the Wide Field Imager of the ATHENA X-Ray Observatory
The ATHENA X-ray Observatory-IXO is a planned multinational orbiting X-ray
observatory with a focal length of 11.5m. ATHENA aims to perform pointed
observations in an energy range from 0.1 keV to 15 keV with high sensitivity.
For high spatial and timing resolution imaging and spectroscopic observations
the 640x640 pixel^2 large DePFET-technology based Wide field Imager (WFI) focal
plane detector, providing a field of view of 18 arcsec will be the main
detector. Based on the actual mechanics, thermal and shielding design we
present estimates for the WFI cosmic ray induced background obtained by the use
of Monte-Carlo simulations and possible background reduction measures.Comment: IEEE NSS MIC Conference 2011, Valencia, Spai
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