Spectral properties of the trap model on sparse networks

One of the simplest models for the slow relaxation and aging of glasses is the trap model by Bouchaud and others, which represents a system as a point in configuration-space hopping between local energy minima. The time evolution depends on the transition rates and the network of allowed jumps between the minima. We consider the case of sparse configuration-space connectivity given by a random graph, and study the spectral properties of the resulting master operator. We develop a general approach using the cavity method that gives access to the density of states in large systems, as well as localisation properties of the eigenvectors, which are important for the dynamics. We illustrate how, for a system with sparse connectivity and finite temperature, the density of states and the average inverse participation ratio have attributes that arise from a non-trivial combination of the corresponding mean field (fully connected) and random walk (infinite temperature) limits. In particular, we find a range of eigenvalues for which the density of states is of mean-field form but localisation properties are not, and speculate that the corresponding eigenvectors may be concentrated on extensively many clusters of network sites.Comment: 41 pages, 15 figure

QCD Corrections to Electroweak Annihilation Decays of Superheavy Quarkonia

QCD corrections to all the allowed decays of superheavy groundstate quarkonia into electroweak gauge and Higgs bosons are presented. For quick estimates, approximations that reproduce the exact results within less than at worst two percent are also given.Comment: 20 pages RevTeX, 9 figures. The complete paper, including figures, is also available via anonymous ftp at (129.13.102.139) as ftp://ttpux2.physik.uni-karlsruhe.de/ttp95-05/ttp95-05.ps, or via www at http://ttpux2.physik.uni-karlsruhe.de/cgi-bin/preprints

Is regulating the solvency of banks counter-productive?

This paper contains a critique of solvency regulation such as imposed on banks by Basel I and II. It argues that banks seeking to maximize rate of return on risk-adjusted capital (RORAC) aim at an optimal level of solvency because on the one hand, solvency S lowers the cost of refinancing; on the other, it ties costly capital. In period 1, exogenous changes in mean returns dµ and in volatility occur, causing optimal adjustments dS * / dµ and dS * / ds in period 2. Since banks reallocate their assets with certain µ and s values in response to the changed solvency level, an endogenous trade-off with slope dµ / ds results in period 3. Both Basel I and II are shown to modify this slope, inducing at least some banks to opt for a higher value of s in certain situations. Therefore, this type of solvency regulation can prove counter-productive

A semi-exact degree condition for Hamilton cycles in digraphs

The paper is concerned with directed versions of Posa's theorem and Chvatal's theorem on Hamilton cycles in graphs. We show that for each a>0, every digraph G of sufficiently large order n whose outdegree and indegree sequences d_1^+ \leq ... \leq d_n^+ and d_1^- \leq >... \leq d_n^- satisfy d_i^+, d_i^- \geq min{i + a n, n/2} is Hamiltonian. In fact, we can weaken these assumptions to (i) d_i^+ \geq min{i + a n, n/2} or d^-_{n - i - a n} \geq n-i; (ii) d_i^- \geq min{i + a n, n/2} or d^+_{n - i - a n} \geq n-i; and still deduce that G is Hamiltonian. This provides an approximate version of a conjecture of Nash-Williams from 1975 and improves a previous result of K\"uhn, Osthus and Treglown

Adequate Capital and Stress Testing for Operational Risks

We describe how the notion of sequential correlations naturally leads to the quantification of operational risk. Our main point is that functional dependencies between mutually supportive processes give rise to non-trivial temporal correlations, which can lead to the occurrence of collective risk events in the form of bursts and avalanches of process failures, and crashes of process networks. We show how the adequate capital for operational risk can be calculated via a stochastic dynamics defined on a topological network of interacting processes. One of the main virtues of the present model is the suitability for capital allocation and stress testing of operational risks

Intermittency in an interacting generalization of the geometric Brownian motion model

We propose a minimal interacting generalization of the geometric Brownian motion model, which turns out to be formally equivalent to a model describing the dynamics of networks of analogue neurons. For sufficiently strong interactions, such systems may have many meta-stable states. Transitions between meta-stable states are associated with macroscopic reorganizations of the system, which can be triggered by random external forcing. Such a system will exhibit intermittent dynamics within a large part of its parameter space. We propose market dynamics as a possible application of this model, in which case random external forcing would correspond to the arrival of important information. The emergence of a model of interacting prices of the type considered here can be argued to follow naturally from a general argument based on integrating out all non-price degrees of freedom from the dynamics of a hypothetical complete description of economic dependences. PACS numbers: 02.50.−r, 05.40.−a, 89.65.Gh, 89.75.Da 1

Zielgerichteter Einsatz von Antibiotika in der Eutergesundheit von Biobetrieben - Integration von tiergesundheitlichen Erfordernissen und Biorichtlinien

The effect of dry cow recommendations on udder health of cows after calving is investigated in 10 conventional Bavarian dairy farms. Information is based on monthly somatic cell count (SCC) measurements during the last 3 months and the result of quarter milk sample bacteriology and SCC (bovicare laboratory). An udder phase was calculated for every individual cow which could be “GREEN” (normal), “YELLOW” and “ORANGE” (mostly infected cows) or “RED” (mostly cows with low cure risk). Within 7 months, 219 cows had complete data to assess the effect of dry cow means (such as antibiotic treatment, teat sealing or no therapy) on SCC after calving. Farmers followed the recommendations in 80 % of the cases. Use of non-antibiotic therapies were recommended in 53% and applied in 43% of the cases. Effects depended on udder phase prior to drying off. Proportions of “unsuspicious cows” (SCC <100k/ml) were 66%, 60% and 48% for GREEN, YELLOW and ORANGE/RED cows, respectively. Targeted dry cow therapy with antibiotics was successful compared to use of antibiotics against recommendations in cows with phases beyond GREEN. The concept of an information based udder health management connects individual cow data as a basis for adequate therapy recommendations in accordance to organic regulations

Holocene palaeosols and aeolian activities in the Umimmalissuaq valley, West Greenland

Aeolian sand sheets and active dunefields preserve an ancient Holocene land surface represented by palaeosols that occur around the present ice margin in the Kangerlussuaq area, West Greenland. To determine the relation between Holocene aeolian activities and periods of soil formation, both substantially dependent on the deglaciation history, palaeosols, aeolian sand sheets and dunefields were analysed using field data, grain size analyses, optically stimulated luminescence dating and AMS 14C data in an area of about 15 km2 of the Umimmalissuaq valley. Palaeosols are developed close to the ice margin (&lt;2 km) in fine-grained aeolian sediment (silt loam) and covered by sandy aeolian layers. Silt contents of palaeosols (partly &gt;60 wt%) are comparable with aeolian sand sheets currently formed at greater distances (4–5 km) from the present ice margin. We propose a transport distance for fine aeolian sediments, in which the palaeosols are formed, of at least 4 km from inboard of the present ice margin. Soil formation of the palaeosols started around 2700 cal. yr b2k. Ages from the youngest parts of the palaeosols suggest a stable period of around 2400 years, allowing for pedogenesis. This period was characterised by low but constant aeolian activity. Since aeolian activity intensified after around 300 cal. yr b2k and is still resulting in active dunefields with coarse and medium sand accumulation, the ice margin must have reached its present position at that time. </jats:p