Cooperation in a resource extraction game

An exhaustible stock of resources may be exploited by N players. An arbitrarily long duration of the game is only possible, if the utility function satisfies certain restrictions at small values R of extraction. We find that stability against unilateral defection occurs if the elasticity of the marginal utility turns out to be larger than (N - 1 )/N, however independent of the value of the discount factor. Hence we find that cooperation does not depend on the discount factor for a certain range of elasticities. Analogy to phase transitions in statistical physics is discussed.

Multiplicative Approximations, Optimal Hypervolume Distributions, and the Choice of the Reference Point

Many optimization problems arising in applications have to consider several objective functions at the same time. Evolutionary algorithms seem to be a very natural choice for dealing with multi-objective problems as the population of such an algorithm can be used to represent the trade-offs with respect to the given objective functions. In this paper, we contribute to the theoretical understanding of evolutionary algorithms for multi-objective problems. We consider indicator-based algorithms whose goal is to maximize the hypervolume for a given problem by distributing {\mu} points on the Pareto front. To gain new theoretical insights into the behavior of hypervolume-based algorithms we compare their optimization goal to the goal of achieving an optimal multiplicative approximation ratio. Our studies are carried out for different Pareto front shapes of bi-objective problems. For the class of linear fronts and a class of convex fronts, we prove that maximizing the hypervolume gives the best possible approximation ratio when assuming that the extreme points have to be included in both distributions of the points on the Pareto front. Furthermore, we investigate the choice of the reference point on the approximation behavior of hypervolume-based approaches and examine Pareto fronts of different shapes by numerical calculations

An Iterative Procedure for the Estimation of Drift and Diffusion Coefficients of Langevin Processes

A general method is proposed which allows one to estimate drift and diffusion coefficients of a stochastic process governed by a Langevin equation. It extends a previously devised approach [R. Friedrich et al., Physics Letters A 271, 217 (2000)], which requires sufficiently high sampling rates. The analysis is based on an iterative procedure minimizing the Kullback-Leibler distance between measured and estimated two time joint probability distributions of the process.Comment: 4 pages, 5 figure

Spectroscopic investigations of delaminated and intercalated phyllosilicates

The characteristic feature of phyllosilicates like muscovite (KAl2[Si3AlO10(OH)2] is their layered structure. Due to the resulting anisotropic optical and electrical properties this mineral is an important raw material in paint industries and polymer composites. Crucial for many of these properties is on one hand a high aspect ratio of the stacks, which will be enhanced by delamination of the mineral. On the other hand the exchange of the interlayer cations like potassium changes the chemical properties of the muscovite, its refraction behaviour and surface properties. But these interlayer cations are difficult to access and are not exchangeable under normal conditions. Thus a process for the intercalation of cations like Cu2+, Mg2+ or Zn2+ from super saturated nitrate solutions in autoclaves was developed to reveal a chemically modified mica phase. The extensive modification of the muscovite structure, due to the intercalation is monitored by X-ray diffractometry and several spectroscopic methods. The XRD results strongly suggest the formation of an intercalated irregular mixed-layer phase. This is proven by far infrared spectroscopy which show the simultaneous occurrence of both K+ and Cu2+ in the interlayer region, strongly increasing the interlayer space. 1Investigations in the mid infrared region using diffuse reflectance spectroscopy (DRIFT) suggest a further migration of the intercalated cations deep into the ditrigonal holes of the tetrahedral sheet and their fixation within these holes close to the OH groups

Does the Introduction of IFRS Change the Timeliness of Loss Recognition? Evidence from German Firms

In this paper, we re-evaluate the hypothesis that the introduction of the IFRS has an impact on the timeliness of loss recognition. We test this hypothesis in a data set of public German firms that report according to German-GAAP and IFRS, respectively. The parallel use of the two accounting standards in Germany provides a unique opportunity to contribute to the academic discussion, as well as to the current policy debate on regulatory reform in Germany. Starting from the standard time series concept of conditional conservatism that was initially proposed by Basu (1997), we implement a wide range of test specifications, including (i) a threshold unit-root test specification; (ii) a multivariate approach to outlier detection and (iii) various forms of controlling for fixed effects. We do not find evidence that IFRS and German-GAAP firms differ with respect to their timeliness of loss recognition in any of these specifications - a result that appears surprising in light of the more prudent regulation in the German-GAAP, but is consistent with some earlier findings in the literature.IFRS, German-GAAP, Timely loss recognition, Conservatism

Cell body rocking is a dominant mechanism for flagellar synchronization in a swimming alga

The unicellular green algae Chlamydomonas swims with two flagella, which can synchronize their beat. Synchronized beating is required to swim both fast and straight. A long-standing hypothesis proposes that synchronization of flagella results from hydrodynamic coupling, but the details are not understood. Here, we present realistic hydrodynamic computations and high-speed tracking experiments of swimming cells that show how a perturbation from the synchronized state causes rotational motion of the cell body. This rotation feeds back on the flagellar dynamics via hydrodynamic friction forces and rapidly restores the synchronized state in our theory. We calculate that this `cell body rocking' provides the dominant contribution to synchronization in swimming cells, whereas direct hydrodynamic interactions between the flagella contribute negligibly. We experimentally confirmed the coupling between flagellar beating and cell body rocking predicted by our theory. This work appeared also in the Proceedings of the National Academy of Science of the U.S.A as: Geyer et al., PNAS 110(45), p. 18058(6), 2013.Comment: 40 pages, 15 color figure