A critical test of empirical mass loss formulae applied to individual giants and supergiants

To test our new, improved Reimers-type mass-loss relation, given by Schroder & Cuntz in 2005 (ApJL 630, L73), we take a look at the best studied galactic giants and supergiants - particularly those with spatially resolved circumstellar shells and winds, obtained directly or by means of a companion acting as a probing light source. Together with well-known physical parameters, the selected stars provide the most powerful and critical observational venues for assessing the validity of parameterized mass-loss relations for cool winds not driven by molecules or dust. In this study, star by star, we compare our previously published relation with the original Reimers relation (1975), the Lamers relation (1981), and the two relations by de Jager and his group (1988, 1990). The input data, especially the stellar masses, have been constrained using detailed stellar evolution models. We find that only the relationship by Schroder & Cuntz agrees, within the error bars, with the observed mass-loss rates for all giants and supergiants.Comment: 11 pages, 5 Figs. accepted by Astronomy & Astrophysic

Hypergeometric representation of a four-loop vacuum bubble

In this article, we present a new analytic result for a certain single-mass-scale four-loop vacuum (bubble) integral. We also discuss its systematic \e-expansion in d=4-2\e as well as d=3-2\e dimensions, the coefficients of which are expressible in terms of harmonic sums at infinity.Comment: 5 pages, to appear in the proceedings of the conference "Loops and Legs", Eisenach, 200

Populationsgenetische Differenzierung beim Eichenwickler (Tortrix viridana L.) und seiner Wirtspflanze (Quercus robur L.) anhand nukleärer Genmarker

In Western Europe pedunculate oak (Quercus robur L.) is the forest tree with the highest number of phytophagous insect species (Yela & Lawton 1997). One of these, the green oak leaf roller Tortrix viridana L. is an oligophagous herbivorous moth with a host range limited to the genus Quercus (Hunter 1990, Du Merle 1999). During outbreaks, T. viridana often leads to defoliation of oaks in spring. The abundance of T. viridana is subject to the population size fluctuations typical for herbivorous insects, where periods of small population sizes (latent periods) alternate with periods of high population sizes (outbreak) (e.g. Schütte 1957, Horstmann 1984). Apart from many experimental studies on population dynamics of the moth (e.g. Hunter 1990, Du Merle 1999, Ivashov & al. 2002) so far little attention has been paid to the genetic variation within the species as an important aspect of the genetics of this host-parasite interaction. Simchuk & al. (1999) found changes in the heterozygosity level of different isozyme loci during outbreaks in T. viridana and molecular markers for T. viridana have been developed for analyses of genetic variation within and among populations (Schroeder & Scholz 2005). But, investigations of genetic variation within and among populations of forest pest species are important to predict future pest outbreaks. So far the processes outbreaks based on are not entirely clarified, however it is known that migration plays a major role. Using molecular markers investigations of the genetic variation are possible and offer the opportunity to analyse distribution events. In this paper first results are presented concerning the genetic variation of the green oak leaf roller at three geographic scales: (1) among trees within a population, (2) among populations at a small spatial scale of about 150 km and (3) among populations at a broader geographic scale up to 3000 km. Furthermore results of the genetic variation of oaks at the small spatial scale are represented.Populationen des grünen Eichenwicklers (Tortrix viridana L., Lepidoptera: Tortricidae) und der Stieleiche (Quercus robur L., Fagaceae) wurden auf genetische Differenzierungen mit Hilfe von Kern-DNA-Markern untersucht. Insgesamt wurden 14 Eichenbestände in Nordrhein-Westfalen (NRW) und 7 weitere in verschiedenen Regionen Europas in die Untersuchung einbezogen. Weder für die Eiche noch für den Eichenwickler sind genetische Differenzierungen der Populationen auf einer kleinen geographischen Skala (etwa 150 km) nachweisbar, jedoch zeigen die Eichenpopulationen eine zunehmende genetische Distanz mit zunehmender geographischer Distanz. Für den Eichenwickler konnten innerhalb von Populationen in einem Radius von etwa 40 m Familienstrukturen ermittelt werden und auf einer kontinentalen Skala lassen sich die Ergebnisse für den Eichenwickler mit einer „isolation by distance“ erklären

On the valuation of Paris options: foundational results

This paper adresses the valuation of the Paris barrier options proposed by Yor, Jeanblanc-Picque, and Chesnay (Advances in Applied Probability, 29(1997), 165-184) using the Laplace transform approach. Based on suggestions by Pliska the notion of Paris options is extended such that their valuation is possible at any point during their lifespan. The Laplace transforms derived by Yor et al. are modified when necessary, and their basic analytic properties are discussed.Comment: 16 Pages, 2 Figure

Searches for ttˉHt\bar{t}H and tHtH with H→bbˉH\to b\bar b

The associated production of a Higgs boson with a top quark-antiquark pair ($\text{t}\bar{\text{t}}\text{H}$ production) or with a single top quark ($\text{tH}$ production) allows a direct measurement of the top-Higgs-Yukawa coupling with minimal model dependence. In this article, recent results of searches for $\text{t}\bar{\text{t}}\text{H}$ and $\text{tH}$ production in the $\text{H}\rightarrow\text{b}\bar{\text{b}}$ channel performed by the ATLAS and CMS experiments are reviewed. The analyses use pp collision data collected at a centre-of-mass energy of 13$\,$TeV corresponding to an integrated luminosity of up to 13.2$\,$fb${}^{-1}$.Comment: TOP2016 conferenc

The implied equity risk premium - an evaluation of empirical methods

A new approach of estimating a forward-looking equity risk premium (ERP) is to calculate an implied risk premium using present value (PV) formulas. This paper compares implied risk premia obtained from different PV models and evaluates them by analyzing their underlying firm-specific cost-of-capital estimates. It is shown that specific versions of dividend discount models (DDM) and residual income models (RIM) lead to similar ERP estimates. However, cross-sectional regression tests of individual firm risk suggest that there are qualitative differences between both approaches. Expected firm risk obtained from the DDM is more in line with standard asset pricing models and performs better in predicting future stock returns than estimates from the RIM

Linearizability of Non-expansive Semigroup Actions on Metric Spaces

We show that a non-expansive action of a topological semigroup S on a metric space X is linearizable iff its orbits are bounded. The crucial point here is to prove that X can be extended by adding a fixed point of S, thus allowing application of a semigroup version of the Arens-Eells linearization, iff the orbits of S in X are bounded