Quantum fluctuations in the open universe

We solve a continuing controversy when dealing with density fluctuations in open Friedman-Robertson-Walker universes, on the physical relevance of a class of exponential modes. We show explicitly and rigorously that these modes enter the expansion of quantum fields. In the maximally symmetric de Sitter case, encountered in inflationary models, they are excited for fields with mass below a critical value. They are seen to be responsible for the breaking of the de Sitter symmetry for a massless field. We provide an exact calculation of the power spectrum for any mass. Our method is free of the divergences that appear in earlier treatments. We extend the construction to a generic open FRW universe

Lasing on a narrow transition in a cold thermal strontium ensemble

Highly stable laser sources based on narrow atomic transitions provide a promising platform for direct generation of stable and accurate optical frequencies. Here we investigate a simple system operating in the high-temperature regime of cold atoms. The interaction between a thermal ensemble of $^{88}$Sr at mK temperatures and a medium-finesse cavity produces strong collective coupling and facilitates high atomic coherence which causes lasing on the dipole forbidden $^1$S$_0 \leftrightarrow ^3$P$_1$ transition. We experimentally and theoretically characterize the lasing threshold and evolution of such a system, and investigate decoherence effects in an unconfined ensemble. We model the system using a Tavis-Cummings model, and characterize velocity-dependent dynamics of the atoms as well as the dependency on the cavity-detuning.Comment: 9 pages, 7 figure

Non-linear Spectroscopy of Sr Atoms in an Optical Cavity for Laser Stabilization

We study the non-linear interaction of a cold sample of strontium-88 atoms coupled to a single mode of a low finesse optical cavity in the so-called bad cavity limit and investigate the implications for applications to laser stabilization. The atoms are probed on the weak inter-combination line \lvert 5s^{2} \, ^1 \textrm{S}_0 \rangle \,-\, \lvert 5s5p \, ^3 \textrm{P}_1 \rangle at 689 nm in a strongly saturated regime. Our measured observables include the atomic induced phase shift and absorption of the light field transmitted through the cavity represented by the complex cavity transmission coefficient. We demonstrate high signal-to-noise-ratio measurements of both quadratures - the cavity transmitted phase and absorption - by employing FM spectroscopy (NICE-OHMS). We also show that when FM spectroscopy is employed in connection with a cavity locked to the probe light, observables are substantially modified compared to the free space situation where no cavity is present. Furthermore, the non-linear dynamics of the phase dispersion slope is experimentally investigated and the optimal conditions for laser stabilization are established. Our experimental results are compared to state-of-the-art cavity QED theoretical calculations.Comment: 7 pages, 4 figure

Continental-scale patterns of pathogen prevalence: a case study on the corncrake

Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence

Systematische Erfassung der Prävalenz und Schweregradausprägung von Komorbiditäten bei älteren Tumorpatienten mittels der Cumulative Illness Rating Scale for Geriatrics (CIRS-G) und Vergleich mit jüngeren Tumorpatienten und älteren Patienten ohne Malignom

In Zukunft ist v. a. aufgrund der demographischen Entwicklung eine deutliche Zunahme der Inzidenz maligner Neoplasien in Dtl. zu erwarten. Ältere Patienten mit Tumorerkrankungen unterscheiden sich in verschiedenen Merkmalen von jüngeren. Mit Hilfe eines sog. Geriatrischen Assessments (GA) können diese Besonderheiten des geriatrisch-onkologischen Patienten systematisch erfasst werden, um eine Aussage über bspw. Prognose oder Therapieverträglichkeit zu liefern und zu entscheiden, inwieweit eine Abweichung von der üblichen Therapie (wie sie bei jüngeren Patienten angewendet wird) notwendig ist. Die vorliegende Arbeit untersuchte die Komorbiditäten als wesentlichen Teil des GA mit der Cumulative Illness Rating Scale for Geriatrics (CIRS-G) vor Beginn einer spezifischen Therapie an 536 Patienten. Es wurden drei Patientengruppen definiert: Ältere Tumorpatienten (N=231, ÄTP), jüngere Tumorpatienten (N=172, JTP) und ältere Patienten ohne Malignom mit nichtmaligner internistischer Grunderkrankung, die zur Aufnahme ins Universitätsklinikum Jena führte (N=133, NTP). Maligne Grunderkrankungen bei Tumorpatienten waren zu 56,3 % hämatologisch (43,7 % solide). Häufigste Grunderkrankungen bei NTP waren Diabetes mellitus und Herz-Kreislauf-Erkrankungen. ÄTP hatten durchschnittlich 5,5 Komorbiditäten (JTP: 4,0; NTP: 6,9). Eine ähnliche Verteilung fand sich beim Summenscore (ältere TP: 10,3; jüngere TP: 6,8; NTP: 12,1). Die Korrelation der Parameter mit dem Lebensalter war gering bis mittelstark. Die häufigsten von Komorbiditäten betroffenen Organsysteme bei ÄTP waren das Gefäßsystem, Bluterkrankungen, das Herz, pulmonale sowie endokrin-metabolische Erkrankungen. Es handelt sich um eine umfassende Analyse der Prävalenz inklusive Beurteilung des Schweregrads von Komorbiditäten bei älteren Tumorpatienten sowie zweier Vergleichsgruppen. Mögliche Fehlerquellen und Limitationen der Untersuchungsmethode werden ausführlich diskutiert