A field-theoretic approach to the Wiener Sausage

The Wiener Sausage, the volume traced out by a sphere attached to a Brownian particle, is a classical problem in statistics and mathematical physics. Initially motivated by a range of field-theoretic, technical questions, we present a single loop renormalised perturbation theory of a stochastic process closely related to the Wiener Sausage, which, however, proves to be exact for the exponents and some amplitudes. The field-theoretic approach is particularly elegant and very enjoyable to see at work on such a classic problem. While we recover a number of known, classical results, the field-theoretic techniques deployed provide a particularly versatile framework, which allows easy calculation with different boundary conditions even of higher momenta and more complicated correlation functions. At the same time, we provide a highly instructive, non-trivial example for some of the technical particularities of the field-theoretic description of stochastic processes, such as excluded volume, lack of translational invariance and immobile particles. The aim of the present work is not to improve upon the well-established results for the Wiener Sausage, but to provide a field-theoretic approach to it, in order to gain a better understanding of the field-theoretic obstacles to overcome.Comment: 45 pages, 3 Figures, Springer styl

COST725 – establishing a European phenological data platform for climatological applications: major results

COST – European COoperation in the field of Scientific and Technical Research – is the oldest and widest intergovernmental European network for cooperation in research. COST Action 725 (running from 2004 to 2009) aimed at and succeeded in establishing a European data base of phenological observations, classifying the data according to one common system and using the data in scientific peer reviewed papers. COST725 organized many workshops and conferences that helped to bring together not only the European, but also the global, phenological community. One of the highlights of COST725 was the boxed entry "Phenological responses to climate in Europe: the COST725 project" in the AR4 of IPCC in 2007. And last, but not least, although the action ended in April 2009 a follow up will be launched in 2010 under EUMETNET/ECSN