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Université de Fribourg

Minority games with heterogeneous timescales

Mosetti, Giancarlo ; Challet, Damien ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2006, vol. 365, no. 2, p. 529-542

Minority games where groups of agents remember, react or incorporate information with different timescales are investigated. We support our findings by analytical arguments whenever possible.

Université de Fribourg

Exploring an opinion network for taste prediction: an empirical study

Blattner, Marcel ; Zhang, Yi-Cheng ; Maslov, Sergei

In: Physica A: Statistical and Theoretical Physics, 2007, vol. 373, no. 1, p. 753-758

We develop a simple statistical method to find affinity relations in a large opinion network which is represented by a very sparse matrix. These relations allow us to predict missing matrix elements. We test our method on the Eachmovie data of thousands of movies and viewers. We found that significant prediction precision can be achieved and it is rather stable. There is an intrinsic limit to...

Université de Fribourg

Decoding information from noisy, redundant, and intentionally distorted sources

Yu, Yi-Kuo ; Zhang, Yi-Cheng ; Laureti, Paolo ; Moret, Lionel

In: Physica A: Statistical and Theoretical Physics, 2006, vol. 371, no. 2, p. 732-744

Advances in information technology reduce barriers to information propagation, but at the same time they also induce the information overload problem. For the making of various decisions, mere digestion of the relevant information has become a daunting task due to the massive amount of information available. This information, such as that generated by evaluation systems developed by various web...

Université de Fribourg

Information filtering via iterative refinement

Laureti, Paolo ; Moret, Lionel ; Zhang, Yi-Cheng ; Yu, Yi-Kou

In: Europhysics Letters, 2006, vol. 75, no. 6, p. 1006-1012

With the explosive growth of accessible information, expecially on the Internet, evaluation-based filtering has become a crucial task. Various systems have been devised aiming to sort through large volumes of information and select what is likely to be more relevant. In this letter we analyse a new ranking method, where the reputation of information providers is determined self-consistently.

Université de Fribourg

Referee networks and their spectral properties

Slanina, F. ; Zhang, Yi-Cheng

In: Acta Physica Polonica B, 2005, vol. 36(9), p. 2797

The bipartite graph connecting products and reviewers of that product is studied empirically in the case of amazon.com. We find that the network has power-law degree distribution on the side of reviewers, while on the side of products the distribution is better fitted by stretched exponential. The spectrum of normalised adjacency matrix shows power-law tail in the density of states. Establishing...

Université de Fribourg

Towards a new information theory

Zhang, Yi-Cheng

In: International Journal of Modern Physics B, 2004, vol. 18, p. 2361-2365

Université de Fribourg

Ecology of active and passive players and their impact on information selection

Bianconi, Ginestra ; Laureti, Paolo ; Yu, Yi-Kou ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2004, vol. 332, p. 519-532

Is visitors’ attendance a fair indicator of a web site's quality? Internet sub-domains are usually characterized by power-law distributions of visits, thus suggesting a rich-get-richer process. If this is the case, the number of visits is not a relevant measure of quality. If, on the other hand, there are active players, i.e., visitors who can tell the value of the information available, better...

Université de Fribourg

Selection by pairwise comparisons with limited resources

Laureti, Paolo ; Mathiesen, Joachim ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2004, vol. 338, p. 596-604

We analyze different methods of sorting and selecting a set of objects by their intrinsic value, via pairwise comparisons whose outcome is uncertain. After discussing the limits of repeated Round Robins, two new methods are presented: The ran-fil requires no previous knowledge on the set under consideration, yet displaying good performances even in the least favorable case. The min-ent method...

Université de Fribourg

Aggregating partial, local evaluations to achieve global ranking

Laureti, Paolo ; Moret, Lionel ; Zhang, Yi-Cheng

In: Physica A: Statistical Mechanics and its Applications, 2005, vol. 345, 3-4, p. 705-712

We analyze some voting models mimicking online evaluation systems intended to reduce the information overload. The minimum number of operations needed for a system to be effective is analytically estimated. When herding effects are present, linear preferential attachment marks a transition between trustful and biased reputations.

Université de Fribourg

Supply and demand law under limited information

Zhang, Yi-Cheng

We present a model for the supply-demand law with quality and limited information capability. We postulate that imperfect information permeates in almost all economic transactions to varying degrees. Through a simple model we outline a research agenda that re-examines many standard issues in economics. Our analysis shows that whereas imperfect information can be improved, it leads to new...