Improved real-time dynamics from imaginary frequency lattice simulations

The computation of real-time properties, such as transport coefficients or bound state spectra of strongly interacting quantum fields in thermal equilibrium is a pressing matter. Since the sign problem prevents a direct evaluation of these quantities, lattice data needs to be analytically continued from the Euclidean domain of the simulation to Minkowski time, in general an ill-posed inverse problem. Here we report on a novel approach to improve the determination of real-time information in the form of spectral functions by setting up a simulation prescription in imaginary frequencies. By carefully distinguishing between initial conditions and quantum dynamics one obtains access to correlation functions also outside the conventional Matsubara frequencies. In particular the range between $\omega_0$ and $\omega_1=2\pi T$, which is most relevant for the inverse problem may be more highly resolved. In combination with the fact that in imaginary frequencies the kernel of the inverse problem is not an exponential but only a rational function we observe significant improvements in the reconstruction of spectral functions, demonstrated in a simple 0+1 dimensional scalar field theory toy model.Comment: 8 pages, 5 figures, Talk given at the XXXVth International Symposium on Lattice Field Theory, June 18-24, 2017, Granada, Spai

Classes of Skorokhod Embeddings for the Simple Symmetric Random Walk

The Skorokhod Embedding problem is well understood when the underlying process is a Brownian motion. We examine the problem when the underlying is the simple symmetric random walk and when no external randomisation is allowed. We prove that any measure on Z can be embedded by means of a minimal stopping time. However, in sharp contrast to the Brownian setting, we show that the set of measures which can be embedded in a uniformly integrable way is strictly smaller then the set of centered probability measures: specifically it is a fractal set which we characterise as an iterated function system. Finally, we define the natural extension of several known constructions from the Brownian setting and show that these constructions require us to further restrict the sets of target laws

Yellow fever disease : density equalizing mapping and gender analysis of international research output

Background: A number of scientific papers on yellow fever have been published but no broad scientometric analysis on the published research of yellow fever has been reported. The aim of the article based study was to provide an in-depth evaluation of the yellow fever field using large-scale data analysis and employment of bibliometric indicators of production and quantity. Methods: Data were retrieved from the Web of Science database (WoS) and analyzed as part of the NewQis platform. Then data were extracted from each file, transferred to databases and visualized as diagrams. Partially by means of density-equalizing mapping makes the findings clear and emphasizes the output of the analysis. Results: In the study period from 1900 to 2012 a total of 5,053 yellow fever-associated items were published by 79 countries. The United States (USA) having the highest publication rate at 42% (n = 751) followed by far from Brazil (n = 203), France (n = 149) and the United Kingdom (n = 113). The most productive journals are the "Public Health Reports", the "American Journal of Tropical Medicine and Hygiene" and the "Journal of Virology". The gender analysis showed an overall steady increase of female authorship from 1950 to 2011. Brazil is the only country of the five most productive countries with a higher proportion of female scientists. Conclusions: The present data shows an increase in research productivity over the entire study period, in particular an increase of female scientists. Brazil shows a majority of female authors, a fact that is confirmed by other studies

Perception of stress-related working conditions in hospitals (iCept-study): a comparison between physicians and medical students

Background: The students' perception of working conditions in hospitals hasn't been subject of research in Germany so far. However the perception plays an important role talking about the sustainability of working conditions. The iCept Study wants to examine the perception of medical students compared to the perception of practicing physicians. Methods: The perception will be investigated with a redesigned questionnaire based upon two established and validated questionnaires. The two samples built for this study (students and physician) will be chosen from members of the labor union Marburger Bund. The iCept-Study is designed as an anonymized online-survey. Discussion: The iCept-Study is thought to be the basis of ongoing further investigations regarding the perception of working conditions in hospitals. The results shall serve the facilitation of improving working conditions