Emergence of Network Structure in Models of Collective Evolution and Evolutionary Dynamics

We consider an evolving network of a fixed number of nodes. The allocation of edges is a dynamical stochastic process inspired by biological reproduction dynamics, namely by deleting and duplicating existing nodes and their edges. The properties of the degree distribution in the stationary state is analysed by use of the Fokker-Planck equation. For a broad range of parameters exponential degree distributions are observed. The mechanism responsible for this behaviour is illuminated by use of a simple mean field equation and reproduced by the Fokker-Planck equation treating the degree-degree correlations approximately. In the limit of zero mutations the degree distribution becomes a power law.Comment: 10 pages, 1 figur

Optimal degrees of transparency in monetary policymaking

According to most academics and policymakers, transparency in monetary policymaking is desirable. I examine this proposition in a small theoretical model emphasizing forwardlooking private sector behavior. Transparency makes it easier for price setters to infer the central bank's future policy intentions, thereby making current inflation more responsive to policy actions. This induces the central bank to pay more attention to inflation rather than output gap stabilization. Then, transparency may be disadvantageous. It may actually be a policy-distorting straitjacket if the central bank enjoys low-inflation credibility, and there is need for active monetary stabilization policy. -- Den meisten Akademikern und politischen Entscheidungsträgern zufolge ist Transparenz in der Geldpolitik wünschenswert. Ich untersuche diese Behauptung anhand eines kleinen theoretischen Models, das das vorausschauende Verhalten des privaten Sektors hervorhebt. Transparenz erleichtert es denjenigen, die Preise festsetzen, auf die künftigen geldpolitischen Absichten der Zentralbank zu schließen, wodurch die laufende Inflation stärker auf stabilitätspolitische Maßnahmen reagiert. Dies führt dazu, dass die Zentralbank sich eher auf die Inflation als auf die Stabilisierung der Produktionslücke konzentriert. In diesem Fall kann Transparenz negative Folgen haben. Sie kann sich sogar als eine die Geldpolitik verzerrende Zwangsjacke herausstellen, wenn die Zentralbank sich stabilitätspolitischer Glaubwürdigkeit erfreut und eine aktive monetäre Stabilisierungspolitik benötigt wird.Transparenz,Geldpolitik,Zentralbankinstitutionen,Transparency,monetary policy,central bank institutions

Optimal Degrees of Tranaparency in Monetary Policymaking.

According to most academics and policymakers, transparency in monetary policymaking is desirable. I examine this proposition in a small theoretical model emphasizing forward-looking private sector behavior. Transparency makes it easier for price setters to infer the central bank's future policy intentions, thereby making current inflation more responsive to policy actions. This induces the central bank to pay more attention to inflation rather than output gap stabilization. Then, transparency may be disadvantageous. It may actually be a policy-distorting straitjacket if the central bank enjoys low-inflation credibility, and there is need for active monetary stabilization policy.

Visualization of database structures for information retrieval

This paper describes the Book House system, which is designed to support children's information retrieval in libraries as part of their education. It is a shareware program available on CD‐ROM or floppy disks, and comprises functionality for database searching as well as for classifying and storing book information in the database. The system concept is based on an understanding of children's domain structures and their capabilities for categorization of information needs in connection with their activities in schools, in school libraries or in public libraries. These structures are visualized in the interface by using metaphors and multimedia technology. Through the use of text, images and animation, the Book House encourages children ‐ even at a very early age ‐ to learn by doing in an enjoyable way, which plays on their previous experiences with computer games. Both words and pictures can be used for searching; this makes the system suitable for all age groups. Even children who have not yet learned to read properly can, by selecting pictures, search for and find those books they would like to have read aloud. Thus, at the very beginning of their school life, they can learn to search for books on their own. For the library community, such a system will provide an extended service which will increase the number of children's own searches and also improve the relevance, quality and utilization of the book collections in the libraries. A market research report on the need for an annual indexing service for books in the Book House format is in preparation by the Danish Library Centre A/S

Creep of superconducting vortices in the limit of vanishing temperature: A fingerprint of off-equilibrium dynamics

We theoretically study the creep of vortex matter in superconductors. The low temperatures experimental phenomenology, previously interpreted in terms of ``quantum tunnelling'' of vortices, is reproduced by Monte Carlo simulations of a purely ``classical'' vortex model. We demonstrate that a non-zero creep rate in the limit of vanishing temperature is to be expected in systems with slow relaxations as a consequence of their off-equilibrium evolution in a complex free energy landscape.Comment: extended references, published versio