Infection Spreading and Source Identification: A Hide and Seek Game

The goal of an infection source node (e.g., a rumor or computer virus source) in a network is to spread its infection to as many nodes as possible, while remaining hidden from the network administrator. On the other hand, the network administrator aims to identify the source node based on knowledge of which nodes have been infected. We model the infection spreading and source identification problem as a strategic game, where the infection source and the network administrator are the two players. As the Jordan center estimator is a minimax source estimator that has been shown to be robust in recent works, we assume that the network administrator utilizes a source estimation strategy that can probe any nodes within a given radius of the Jordan center. Given any estimation strategy, we design a best-response infection strategy for the source. Given any infection strategy, we design a best-response estimation strategy for the network administrator. We derive conditions under which a Nash equilibrium of the strategic game exists. Simulations in both synthetic and real-world networks demonstrate that our proposed infection strategy infects more nodes while maintaining the same safety margin between the true source node and the Jordan center source estimator

Detecting the Influence of Spreading in Social Networks with Excitable Sensor Networks

Detecting spreading outbreaks in social networks with sensors is of great significance in applications. Inspired by the formation mechanism of human's physical sensations to external stimuli, we propose a new method to detect the influence of spreading by constructing excitable sensor networks. Exploiting the amplifying effect of excitable sensor networks, our method can better detect small-scale spreading processes. At the same time, it can also distinguish large-scale diffusion instances due to the self-inhibition effect of excitable elements. Through simulations of diverse spreading dynamics on typical real-world social networks (facebook, coauthor and email social networks), we find that the excitable senor networks are capable of detecting and ranking spreading processes in a much wider range of influence than other commonly used sensor placement methods, such as random, targeted, acquaintance and distance strategies. In addition, we validate the efficacy of our method with diffusion data from a real-world online social system, Twitter. We find that our method can detect more spreading topics in practice. Our approach provides a new direction in spreading detection and should be useful for designing effective detection methods

Foreign Exchange Intervention When Interest Rates Are Zero: Does the Portfolio Balance Channel Matter After All?

The Japanese zero-interest rate period provides a “natural experiment” for investigating the effectiveness and transmission channels of sterilized intervention when traditional monetary policy options are constrained. This paper takes advantage of the fact that all interventions in the JPY/USD market during the zero-interest rate period are sterilized sales of JPY and, therefore, none of these interventions can signal a future interest rate decrease. In order to further assess through which transmission channel these interventions work, the analysis integrates official daily Japanese intervention data with a comprehensive set of rumors data that capture interventions of which the market is aware. Market awareness is a necessary condition for intervention to disseminate information and work through channels other than the portfolio balance channel. The results of the time series analysis show that intervention, on average, induces a statistically and economically significant same-day depreciation of the JPY. Market awareness is shown to be unimportant. Consequently, the effects of Japanese interventions during the zero-interest rate period are consistent only with the portfolio balance channel. This is a remarkable finding, demonstrating that sterilized intervention is, in principle, an independent policy instrument.exchange rates; foreign exchange market intervention; channels of transmission

Mixing navigation on networks

In this Letter, we proposed a mixing navigation mechanism, which interpolates between random-walk and shortest-path protocol. The navigation efficiency can be remarkably enhanced via a few routers. Some advanced strategies are also designed: For non-geographical scale-free networks, the targeted strategy with a tiny fraction of routers can guarantee an efficient navigation with low and stable delivery time almost independent of network size. For geographical localized networks, the clustering strategy can simultaneously increase the efficiency and reduce the communication cost. The present mixing navigation mechanism is of significance especially for information organization of wireless sensor networks and distributed autonomous robotic systems.Comment: 4 pages, and 7 figure

Foreign exchange intervention when interest rates are zero: does the portfolio balance channel matter after all?

The Japanese zero-interest rate period provides a "natural experiment" for investigating the effectiveness and transmission channels of sterilized intervention when traditional monetary policy options are constrained. This paper takes advantage of the fact that all interventions in the JPY/USD market during the zero-interest rate period are sterilized sales of JPY and, therefore, none of these interventions can signal a future interest rate decrease. In order to further assess through which transmission channel these interventions work, the analysis integrates official daily Japanese intervention data with a comprehensive set of rumors data that capture interventions of which the market is aware. Market awareness is a necessary condition for intervention to disseminate information and work through channels other than the portfolio balance channel. The results of the time series analysis show that intervention, on average, induces a statistically and economically significant same-day depreciation of the JPY. Market awareness is shown to be unimportant. Consequently, the effects of Japanese interventions during the zero-interest rate period are consistent only with the portfolio balance channel. This is a remarkable finding, demonstrating that sterilized intervention is, in principle, an independent policy instrument.Monetary policy - Japan ; Transmission mechanism (Monetary policy) ; Foreign exchange ; Financial markets ; Interest rates - Japan