Perfect Competition in an Oligoply (including Bilateral Monopoly)

We show that if limit orders are required to vary smoothly, then strategic (Nash) equilibria of the double auction mechanism yield competitive (Walras) allocations. It is not necessary to have competitors on any side of any market: smooth trading is a substitute for price wars. In particular, Nash equilibria are Walrasian even in a bilateral monopoly.Limit orders, double auction, Nash equilibria, Walras equilibria, mechanism design

On Partial Defaults in Portfolio Credit Risk : A Poisson Mixture Model Approach

Most credit portfolio models exclusively calculate the loss distribution for a portfolio of performing counterparts. Conservative default definitions cause considerable insecurity about the loss for a long time after the default. We present three approaches to account for defaulted counterparts in the calculation of the economic capital. Two of the approaches are based on the Poisson mixture model CreditRisk+ and derive a loss distribution for an integrated portfolio. The third method treats the portfolio of non-performing exposure separately. All three calculations are supplemented by formulae for contributions of the counterpart to the economic capital. --Portfolio credit risk,CreditRisk+,Recovery

Urban Design for Mussolini, Stalin, Salazar, Hitler and Franco During the Interwar Period

Urban design played a central role for the European dictatorships during the 20th century, it served to legitimate the regime, to produce agreement, to demonstrate power, efficiency and speed, it communicated the social, as well as design projects, of the dictatorial regimes domestically and internationally, it tied old experts, as well as new, to the regime. Dictatorial urban design also played an important role after the fall of the dictatorships: It became the object of structural and verbal handling strategies: of demolition, of transformation, of reconstruction, of forgetting, of suppressing, of re-interpretation and of glorification. The topic area is, therefore, both historical and relevant to the present day. The discussion of the topic area is, like it or not, always embedded in the present state of societal engagement with dictatorships. In order to even be able to discuss all of these aspects, different conceptual decisions are necessary. In retrospect, these may seem to many as self-evident, although they are anything but. Our thesis is that there are three methodological imperatives, especially, which allow an expanded approach to the topic area “urban design and dictatorship”. First and above all, the tunnel view, focused on individual dictatorships and neglecting the international dimension, must be overcome. Second, the differences in urban design over the course of a dictatorship, through an appropriate periodisation, should be emphasised. Third, we must strive for an open, flexible, but complex concept of urban design. The main focus lies on the urban design of the most influential dictatorships of the first half of the 20th century: Soviet Union, Fascist Italy and Nazi Germany, including the urban design of the autarky periods in Portugal and Spain. After all, urban design is not just a product of specific historic circumstances. It is a form that continues to have long-term effects, which demonstrates its usefulness and adaptability throughout this process. The urban design products undoubtedly still recall the dictatorial rule under which they were created. However, they are more than a memory space. They are also a living space of the present. They can and should be discussed with respect to their spatial and functional utility for today and tomorrow. Such a perspective is a given for the citizens of a city, but also for city marketing, having marvellous consequences. Only when we do not exclude this dimension a priori, even in academic discussions, can we do justice to the products of dictatorships. And finally, the view of the urban design of dictatorships can and must contribute to the questioning of simplified and naive conceptions of dictatorships. With urban design in mind, we can observe how dictatorships work and how they were able to prevail. In Europe, these questions are of the highest actuality

Towards Optimal Degree-distributions for Left-perfect Matchings in Random Bipartite Graphs

Consider a random bipartite multigraph $G$ with $n$ left nodes and $m \geq n \geq 2$ right nodes. Each left node $x$ has $d_x \geq 1$ random right neighbors. The average left degree $\Delta$ is fixed, $\Delta \geq 2$. We ask whether for the probability that $G$ has a left-perfect matching it is advantageous not to fix $d_x$ for each left node $x$ but rather choose it at random according to some (cleverly chosen) distribution. We show the following, provided that the degrees of the left nodes are independent: If $\Delta$ is an integer then it is optimal to use a fixed degree of $\Delta$ for all left nodes. If $\Delta$ is non-integral then an optimal degree-distribution has the property that each left node $x$ has two possible degrees, \floor{\Delta} and \ceil{\Delta}, with probability $p_x$ and $1-p_x$, respectively, where $p_x$ is from the closed interval $[0,1]$ and the average over all $p_x$ equals \ceil{\Delta}-\Delta. Furthermore, if $n=c\cdot m$ and $\Delta>2$ is constant, then each distribution of the left degrees that meets the conditions above determines the same threshold $c^*(\Delta)$ that has the following property as $n$ goes to infinity: If $c<c^*(\Delta)$ then there exists a left-perfect matching with high probability. If $c>c^*(\Delta)$ then there exists no left-perfect matching with high probability. The threshold $c^*(\Delta)$ is the same as the known threshold for offline $k$-ary cuckoo hashing for integral or non-integral $k=\Delta$

Resistenter Ölrettich zur Regulierung von Wurzelgallennematoden im ökologischen Landbau

Der Wurzelgallennematode Meloidogyne hapla ist einer der bedeutenden Schaderreger im ökologischen Anbau von Feldgemüse und Kartoffeln. Untersuchungen innerhalb dieses Forschungsvorhabens bestätigten die teils hohen Besatzdichten mit M. hapla auf ökologisch bewirtschafteten Betrieben. Faktoren wie weite Fruchtfolge, hoher Anteil an Leguminosen, Gemüse und Hackfrüchte (Wirtspflanzen) bei gleichzeitig geringem Anteil an Getreide (schlechte Wirtspflanzen) in der Fruchtfolge, kurze Brachezeiten sowie oftmals unzureichende Unkrautregulierung bedeuten ein fast kontinuierliches Vorhandensein an Wirtspflanzen für bestimmte pflanzenparasitäre Nematoden, insbesondere für M. hapla. Mit Ausnahme der im ökologischen Landbau unerwünschten Schwarzbrache sind derzeit keine Verfahren zur gezielten Bekämpfung von M. hapla im ökologischen Landbau praktisch anwendbar. Zur Information der Landwirte und Anbauberater über diesen Schaderreger wurde zu Beginn des Forschungsvorhabens ein Faltblatt zu M. hapla erstellt und verteilt. In dem Forschungsvorhaben wurde dann untersucht, inwieweit durch Anbau gering anfälliger Zwischenfrüchte eine Befallsreduzierung von M. hapla erzielt werden kann. Die Untersuchungen konzentrierten sich auf Ölrettich, da bekannt war, dass Einzelpflanzen einiger Sorten hoch resistent gegenüber diesem Schaderreger sind. Die in der beschreibenden Sortenliste 2002 aufgeführten Ölrettichsorten wurden hinsichtlich ihrer Anfälligkeit für M. hapla charakterisiert. Die geringste Anfälligkeit gegenüber M. hapla zeigte die Sorte 'Commodore' mit einem Pf/Pi = 0,14. Die befallsreduzierende Wirkung dieser Sorte bezüglich M. hapla konnte in Kleinparzellenversuchen bestätigt werden. Bei hohem Ausgangsbesatz wurde die Besatzdichte von M. hapla um 96 % reduziert. Durch Einarbeitung des Pflanzenaufwuchses konnte die befallsreduzierende Wirkung von Ölrettich sogar noch gesteigert werden. Feldversuche auf zwei ökologisch wirtschaftenden Betrieben in Niedersachsen im Jahr 2003 bestätigten die geringe Anfälligkeit von Ölrettich 'Commodore' gegenüber M. hapla. In dem Forschungsvorhaben wurden wichtige Ansätze und Möglichkeiten zur Abwehr von Wurzelgallennematoden im ökologischen Landbau erarbeitet, die durch das BMVEL weiter verfolgt werden sollten. Eine fachliche Information der Landwirte sowie eine intensive Förderung der Resistenzforschung stehen dabei an erster Stelle