Pulsar-wind nebulae in X-rays and TeV gamma-rays

Pulsars are known to be efficient accelerators that produce copious amounts of relativistic particles and inject them into the Galactic medium. The radiation emitted by such a pulsar wind can be seen from radio through gamma-rays as a pulsar-wind nebula (PWN). Here we overview and summarize recent progress in X-ray and TeV observations of PWNe.Comment: 8 pages, 1 fugure, 2 tables to appear in the proceedings of "X-ray Astronomy 2009" conference, Bologna, Italy, September, 2009 published by AIP. Minor changes in the Tables and references. Added acknowledgment

Dynamic analysis of an institutional conflict within the music industry

Peer-to-peer technology has made massive music piracy possible, which, in turn, has arguably had a significant economic impact on the recording industry. Record labels have responded to online piracy with litigation and are also considering self-help measures. It is currently not obvious whether or not these counter-piracy strategies will ultimately stifle online file sharing in the long term. With this paper we attempt to add to our understanding of the conflict within the institution that is the commercial music industry. We conduct an institutional analysis of the industry in transition and extend the traditional pattern modeling methodology with a formal resource-based model of a representative online music network. The model accounts for complex causal interactions between resources, private provision of common goods, free riding and membership dynamics. The numerical implementation of the model is the basis of a decision support system, which is used in a series of computer experiments that emulate anti-piracy scenarios. We show that a peer-to-peer system may be quite resilient to outside disturbances. The experiments also demonstrate that policies rank differently in their effectiveness based on a selected yardstick.Peer-to-peer (P2P) networks; Online File Sharing; Copyright; Simulation

Mitigating the Tragedy of the Digital Commons: the Case of Unsolicited Commercial Email

The growth of unsolicited commercial email imposes increasing costs on organizations and causes considerable aggravation on the part of email recipients. A thriving anti-spam industry addresses some of the frustration. Regulation and various economic and technical means are in the works – all aimed at bringing down the flood of unwanted commercial email. This paper contributes to our understanding of the UCE phenomenon by drawing on scholarly work in areas of marketing and resource ownership and use. Adapting the tragedy of the commons to the email context, we identify a causal structure that drives the direct e-marketing industry. Computer simulations indicate that although filtering may be an effective method to curb UCE arriving at individual inboxes, it is likely to increase the aggregate volume, thereby boosting overall costs. We also examine other response mechanisms, including self-regulation, government regulation, and market mechanisms. The analysis advances understanding of the digital commons, the economics of UCE, and has practical implications for the direct e-marketing industrySPAM; Unsolicited Commercial Email (UCE); Tragedy of the Digital Commons; Simulation

Asset price dynamics with small world interactions under hetereogeneous beliefs

We propose a simple model of a financial market populated with heterogeneous agents. The market represents a network with nodes symbolizing the agents and edges standing for connections between them, thus, embodying local interactions in the market. By local interactions we mean any kind of interplay between the decisions of the agents unaffected by the market mechanism and unrelated to the physical distance between the agents. Using the rewiring procedure we restructure a network from regular lattice to random graph by varying the probability of the agents to switch from one trading strategy to another. We study how the network structure influences the asset price dynamics. The results show that for some intermediate values of the probability to switch, corresponding to a small world network, the price dynamics become reminiscent to the real. While for the boundary values of the probability the dynamics lacks some typical features of the real financial markets.local interactions, networks, small world, heterogeneous beliefs, price dynamics, bifurcations, chaos